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Authors: Rui Yan, Tianle Zhang, Yuan Wang, Wenxiu Wang, Rahat Sharif, Jiale Liu, Qinglong Dong, Haoan Luan, Xuemei Zhang, Han Li, Suping Guo, Guohui Qi and Peng Jia.
Plant Physiology and Biochemistry (2024)
Highlights: • Seventeen GA2-oxidase genes identified in apple clustered into four clades. • MdGA2ox7 responded to cold and salt treatments. • MdGA2ox7 was activated during light-induced anthocyanin accumulation. • MdGA2ox7 alleviated cold and salt stress damage. • MdGA2ox7 promoted anthocyanin biosynthesis.
Abstract: "Apple (Malus domestica Borkh.) is a widely cultivated fruit crop worldwide but often suffers from abiotic stresses such as salt and cold. Gibberellic acid (GA) plays a pivotal in controlling plant development, environmental adaptability, and secondary metabolism. The GA2-oxidase (GA2ox) is responsible for the deactivation of bioactive GA. In this study, seventeen GA2-oxidase genes were identified in the apple genome, and these members could be clustered into four clades based on phylogenetic relationships and conserved domain structures. MdGA2ox7 exhibited robust expression across various tissues, responded to cold and salt treatments, and was triggered in apple fruit peels via light-induced anthocyanin accumulation. Subcellular localization prediction and experiments confirmed that MdGA2ox7 was located in the cytoplasm. Overexpression of MdGA2ox7 in Arabidopsis caused a lower level of active GA and led to GA-deficient phenotypes, such as dwarfism and delayed flowering. MdGA2ox7 alleviated cold and salt stress damage in both Arabidopsis and apple in concert with melatonin (MT). Additionally, MdGA2ox7 enhanced anthocyanin biosynthesis in apple calli and activated genes involved in anthocyanin synthesis. These findings provide new insights into the functions of apple GA2ox in regulating development, stress tolerance, and secondary metabolism."
Authors: Ting Li, Yongqin Wang, Annelore Natran, Yi Zhang, Hao Wang, Kangxi Du, Peng Qin, Hua Yuan, Weilan Chen, Bin Tu, Dirk Inzé and Marieke Dubois.
New Phytologist (2024)
Abstract: "Gibberellic acid (GA) plays a central role in many plant developmental processes and is crucial for crop improvement. DELLA proteins, the core suppressors in the GA signaling pathway, are degraded by GA via the 26S proteasomal pathway to release the GA response. However, little is known about the phosphorylation-mediated regulation of DELLA proteins. In this study, we combined GA response assays with protein–protein interaction analysis to infer the connection between Arabidopsis thaliana DELLAs and the C-TERMINAL DOMAIN PHOSPHATASE-LIKE 3 (CPL3), a phosphatase involved in the dephosphorylation of RNA polymerase II. We show that CPL3 directly interacts with DELLA proteins and promotes DELLA protein stability by inhibiting its degradation by the 26S proteasome. Consequently, CPL3 negatively modulates multiple GA-mediated processes of plant development, including hypocotyl elongation, flowering time, and anthocyanin accumulation. Taken together, our findings demonstrate that CPL3 serves as a novel regulator that could improve DELLA stability and thereby participate in GA signaling transduction."
Authors: Shaofang Wu, Chaoyi Hu, Changan Zhu, Yanfen Fan, Jie Zhou, Xiaojia Xia, Kai Shi, Yanhong Zhou, Christine H. Foyer and Jingquan Yu.
Molecular Plant (2024)
Summary: By physically interacting with and ubiquitinating JAZ4, PUB22 functions as a crucial regulator in JA signaling. The degradation of JAZ4 is promoted by PUB22 but not by the classical SCFCOI1. Meanwhile, JA-activated MYC2 promotes the expression of PUB22, establishing a positive regulatory circuit in JA signaling. Our study provides new insights into the regulation of JA signaling through specific PUB.
Abstract: "Jasmonates (JAs), a class of lipid-derived stress hormones, play a crucial role across an array of plant physiological processes and stress responses. While JA signaling is generally thought to rely dominantly on the degradation of specific JASMONATE-ZIM DOMAIN (JAZ) proteins by SCFCOI1, it remains unclear whether other pathways are involved in the regulation of JAZ protein stability. Here, we report that PUB22, a plant U-box type E3 ubiquitin ligase, plays a vital role in the regulation of the resistance against Helicoverpa armigera and other JA responses in tomato. While COI1 physically interacts with JAZ1/2/5/7, PUB22 physically interacts with JAZ1/3/4/6. PUB22 ubiquitinates JAZ4 to promote its degradation via 26S proteasome pathway. Importantly, pub22 mutants had decreased whilst jaz4 mutants and jaz1 jaz3 jaz4 jaz6 quadruple mutants had enhanced resistance against H. armigera. The hypersensitivity to herbivores for pub22 mutants was partially rescued by JAZ4 mutation. Moreover, PUB22 expression was transcriptionally activated by MYC2, thus forming a positive feedback circuit in JA signaling. Notably, the PUB22-JAZ4 module regulated various JA responses, including the defense against Botrytis cinerea, root elongation inhibition and anthocyanin accumulation. Taken together, PUB22 plays a crucial role in plant response to environmental changes in concert with the COI1-regulated JA signaling by targeting specific JAZs."
Authors: Sylwia Keller-Przybylkowicz, Michal Oskiera , Xueqing Liu, Laiqing Song, Lingling Zhao, Xiaoyun Du, Dorota Kruczynska, Agnieszka Walencik, Norbert Kowara and Grzegorz Bartoszewski.
International Journal of Molecular Sciences (2024)
Abstract: "The red flesh coloration of apples is a result of a biochemical pathway involved in the biosynthesis of anthocyanins and anthocyanidins. Based on apple genome analysis, a high number of regulatory genes, mainly transcription factors such as MYB, which are components of regulatory complex MYB-bHLH-WD40, and several structural genes (PAL, 4CL, CHS, CHI, F3H, DFR, ANS, UFGT) involved in anthocyanin biosynthesis, have been identified. In this study, we investigated novel genes related to the red-flesh apple phenotype. These genes could be deemed molecular markers for the early selection of new apple cultivars. Based on a comparative transcriptome analysis of apples with different fruit-flesh coloration, we successfully identified and characterized ten potential genes from the plant hormone transduction pathway of auxin (GH3); cytokinins (B-ARR); gibberellins (DELLA); abscisic acid (SnRK2 and ABF); brassinosteroids (BRI1, BZR1 and TCH4); jasmonic acid (MYC2); and salicylic acid (NPR1). An analysis of expression profiles was performed in immature and ripe fruits of red-fleshed cultivars. We have uncovered genes mediating the regulation of abscisic acid, salicylic acid, cytokinin, and jasmonic acid signaling and described their role in anthocyanin biosynthesis, accumulation, and degradation. The presented results underline the relationship between genes from the hormone signal transduction pathway and UFGT genes, which are directly responsible for anthocyanin color transformation as well as anthocyanin accumulation during apple-fruit ripening."
Authors: Ru-Feng Song, Xiao-Yu Hu, Wen-Cheng Liu and Hong-Mei Yuan.
Plant Cell Reports (2024)
Key message ABI5 functions in ABA-mediated anthocyanin accumulation in plant response to low phosphate.
Abstract: "Low phosphate (LP)-induced anthocyanin biosynthesis and accumulation play an important role in plant adaptive response to phosphate starvation conditions. However, whether and how the stress phytohormone abscisic acid (ABA) participates in LP-induced anthocyanin accumulation remain elusive. Here, we report that ABA is required for LP-induced anthocyanin accumulation in Arabidopsis thaliana. Disrupting ABA DEFICIENT2 (ABA2), a key ABA-biosynthetic gene, or BETA-GLUCOSIDASE1 (BG1), a major gene implicated in converting conjugated ABA to active ABA, significantly impairs LP-induced anthocyanin accumulation, as LP-induced expression of the anthocyanin-biosynthetic genes Chalcone Synthase (CHS) is dampened in the aba2 and bg1 mutant. In addition, LP-induced anthocyanin accumulation is defective in the mutants of ABA signaling pathway, including ABA receptors, ABA Insensitive2, and the transcription factors ABA Insensitive5 (ABI5), suggesting a role of ABI5 in ABA-mediated upregulation of anthocyanin-biosynthetic genes in plant response to LP. Indeed, LP-induced expression of CHS is repressed in the abi5-7 mutant but further promoted in the ABI5-overexpressing plants compared to the wild-type. Moreover, ABI5 can bind to and transcriptionally activate CHS, and the defectiveness of LP-induced anthocyanin accumulation in abi5-7 can be restored by overexpressing CHS. Collectively, our findings illustrates that ABI5 functions in ABA-mediated LP-induced anthocyanin accumulation in Arabidopsis."
Authors: Jian-Ping An, Rui-Rui Xu, Xiao-Na Wang, Xiao-Wei Zhang, Chun-Xiang You and Yuepeng Han.
Journal of Integrative Plant Biology (2024)
Abstract: "Anthocyanins are secondary metabolites induced by environmental stimuli and developmental signals. The positive regulators of anthocyanin biosynthesis have been reported, whereas the anthocyanin repressors have been neglected. Although the signal transduction pathways of gibberellin (GA) and jasmonic acid (JA) and their regulation of anthocyanin biosynthesis have been investigated, the cross-talk between GA and JA and the antagonistic mechanism of regulating anthocyanin biosynthesis remain to be investigated. In this study, we identified the anthocyanin repressor MdbHLH162 in apple and revealed its molecular mechanism of regulating anthocyanin biosynthesis by integrating the GA and JA signals. MdbHLH162 exerted passive repression by interacting with MdbHLH3 and MdbHLH33, which are two recognized positive regulators of anthocyanin biosynthesis. MdbHLH162 negatively regulated anthocyanin biosynthesis by disrupting the formation of the anthocyanin-activated MdMYB1-MdbHLH3/33 complexes and weakening transcriptional activation of the anthocyanin biosynthetic genes MdDFR and MdUF3GT by MdbHLH3 and MdbHLH33. The GA repressor MdRGL2a antagonized MdbHLH162-mediated inhibition of anthocyanins by sequestering MdbHLH162 from the MdbHLH162-MdbHLH3/33 complex. The JA repressors MdJAZ1 and MdJAZ2 interfered with the antagonistic regulation of MdbHLH162 by MdRGL2a by titrating the formation of the MdRGL2a-MdbHLH162 complex. Our findings reveal that MdbHLH162 integrates the GA and JA signals to negatively regulate anthocyanin biosynthesis. This study provides new information for discovering more anthocyanin biosynthesis repressors and explores the cross-talk between hormone signals."
Authors: Tatiane Jéssica Siebeneichler, Rosane Lopes Crizel, Cesar Valmor Rombaldi and Vanessa Galli.
Phytochemistry Reviews (2024)
Abstract: "The biosynthesis of phenylpropanoids is regulated by a complex molecular, biochemical and physiological network. Modulation of phenylpropanoid metabolism occurs by endogenous (transcription and post-transcription factors, homeostasis modulators, hormones) and extrinsic (biotic and abiotic agents) signals, both during the growth and development of strawberries. In the context of endogenous modulation, during the transition from maturation to ripening of strawberries, the most significant alteration in the synthesis and accumulation of phenylpropanoids occurs, and phytohormones are intensely involved in regulating this event. The phytohormone abscisic acid (ABA) is highlighted, which plays a central role in strawberry ripening and seems necessary for anthocyanin synthesis. In this review, we report the main mechanisms involved before and during the biosynthesis of phenylpropanoid compounds in strawberry ripening, focusing on anthocyanin synthesis."
Authors: Lei Shi, Xing Li,Ying Fu and Changjiang Li.
International Journal of Molecular Sciences (2023)
Abstract: "Anthocyanin accumulation in plants plays important roles in plant growth and development, as well as the response to environmental stresses. Anthocyanins have antioxidant properties and play an important role in maintaining the reactive oxygen species (ROS) homeostasis in plant cells. Furthermore, anthocyanins also act as a “sunscreen”, reducing the damage caused by ultraviolet radiation under high-light conditions. The biosynthesis of anthocyanin in plants is mainly regulated by an MYB-bHLH-WD40 (MBW) complex. In recent years, many new regulators in different signals involved in anthocyanin biosynthesis were identified. This review focuses on the regulation network mediated by different environmental factors (such as light, salinity, drought, and cold stresses) and phytohormones (such as jasmonate, abscisic acid, salicylic acid, ethylene, brassinosteroid, strigolactone, cytokinin, and auxin). We also discuss the potential application value of anthocyanin in agriculture, horticulture, and the food industry."
Authors: Yalin Li, Xinyu Yang, Xuewen Li, Chuang Wang, Guangda Ding, Fangsen Xu, Sheliang Wang, Hongmei Cai, John P. Hammond, Sergey Shabala, Min Yu and Lei Shi.
Plant and Soil (2023)
Abstract: "Aims - The aims of this work were to investigate phosphate starvation responses of Brassica napus (B. napus) under heterogeneous phosphate (Pi) supply and the regulatory role of jasmonic acid (JA) in the systemic response to Pi starvation. Methods - A split-root system with two separated compartments was employed to mimic heterogeneous Pi distribution in the soil and to examine the effect of heterogeneous Pi supply, and JA or DIECA (JA biosynthesis inhibitor) on growth, root morphology, Pi concentration, Acid phosphatase (APase) activity, nutrition uptake, JA concentration and expression of Pi starvation systemically-induced (PSSI) genes of B. napus. Results - Heterogeneous Pi supply systemically modified root morphology that increased the total root surface area (TRSA), total root volume (TRV), total root length (TRL) and total lateral root number (TLRN) of root with local Pi supply (R +) and decreased them of root with local no Pi supply (R-) when compared to root with homogeneous Pi supply (R + +) and root devoid of Pi (R–), respectively. Anthocyanin, APase activity and JA concentration in shoot and root of B. napus were systemically regulated by heterogeneous Pi supply. In addition, heterogeneous Pi supply significantly promoted nutrient uptake when compared with homogeneous no Pi supply. Root morphology of B. napus was significantly changed by exogenous addition of JA or DIECA in a split-root system. JA enhanced Pi starvation response by inducing expression of PSSI genes in shoots and roots. Conclusions - Our results suggest that JA enhances systemic Pi starvation response of B. napus by regulating root morphology, Pi homeostasis and inducing expression of PSSI genes under heterogeneous Pi supply."
Authors: Hongxue Li, Shouwen Wang, Lulu Zhai, Yuhai Cui, Guiliang Tang, Junwei Huo, Xuyan Li and Shaomin Bian.
Plant Biotechnology Journal (2023)
Abstract: "Colour change is an important event during fruit ripening in blueberry. It is well known that miR156/SPLs act as regulatory modules mediating anthocyanin biosynthesis and ethylene plays critical roles during colour change, but the intrinsic connections between the two pathways remain poorly understood. Previously, we demonstrated that blueberry VcMIR156a/VcSPL12 affects the accumulation of anthocyanins and chlorophylls in tomato and Arabidopsis. In this study, we first showed that VcMIR156a overexpression in blueberry led to enhanced anthocyanin biosynthesis, decreased chlorophyll accumulation, and, intriguingly, concomitant elevation in the expression of ethylene biosynthesis genes and the level of the ethylene precursor ACC. Conversely, VcSPL12 enhanced chlorophyll accumulation and suppressed anthocyanin biosynthesis and ACC synthesis in fruits. Moreover, the treatment with ethylene substitutes and inhibitors attenuated the effects of VcMIR156a and VcSPL12 on pigment accumulation. Protein-DNA interaction assays indicated that VcSPL12 could specifically bind to the promoters and inhibit the activities of the ethylene biosynthetic genes VcACS1 and VcACO6. Collectively, our results show that VcMIR156a/VcSPL12 alters ethylene production through targeting VcACS1 and VcACO6, therefore governing fruit colour change. Additionally, VcSPL12 may directly interact with the promoter region of the chlorophyll biosynthetic gene VcDVR, thereby activating its expression. These findings established an intrinsic connection between the miR156/SPL regulatory module and ethylene pathway."
Authors: Hong-Liang Li, Zhi-Ying Liu, Xiao-Na Wang, Yuepeng Han, Chun-Xiang You and Jian-Ping An.
Plant, Cell & Environment (2023)
Abstract: Auxin/indole-3-acetic acid (AUX/IAA) and auxin response factor (ARF) proteins are important components of the auxin signalling pathway, but their ubiquitination modification and the mechanism of auxin-mediated anthocyanin biosynthesis remain elusive. Here, the ARF MdARF5-1 was identified as a negative regulator of anthocyanin biosynthesis in apple, and it integrates auxin and ethylene signals by inhibiting the expression of the ethylene response factor MdERF3. The auxin repressor MdIAA29 decreased the inhibitory effect of MdARF5-1 on anthocyanin biosynthesis by attenuating the transcriptional inhibition of MdERF3 by MdARF5-1. In addition, the E3 ubiquitin ligases MdSINA4 and MdSINA11 played negative and positive regulatory roles in anthocyanin biosynthesis by targeting MdIAA29 and MdARF5-1 for ubiquitination degradation, respectively. MdSINA4 destabilized MdSINA11 to regulate anthocyanin accumulation in response to auxin signalling. In sum, our data revealed the crosstalk between auxin and ethylene signals mediated by the IAA29-ARF5-1-ERF3 module and provide new insights into the ubiquitination modification of the auxin signalling pathway.
Authors: Ying Wang, Jian’an Li, Purui Guo, Qian Liu, Shuangshuang Ren, Lemei Juan, Jiacheng He, Xiaofeng Tan and Jindong Yan.
Planta (2023)
Main conclusion Ectopic expression of Camellia oleifera Abel. gibberellin 20-oxidase 1 caused a taller phenotype, promoted secondary cell wall deposition, leaf enlargement, and early flowering, and reduced chlorophyll and anthocyanin accumulation and seed enlargement phenotype in Arabidopsis.
Abstract: "Plant height and secondary cell wall (SCW) deposition are important plant traits. Gibberellins (GAs) play important roles in regulating plant height and SCWs deposition. Gibberellin 20-oxidase (GA20ox) is an important enzyme involved in GA biosynthesis. In the present study, we identified a GA synthesis gene in Camellia oleifera. The total length of the CoGA20ox1 gene sequence was 1146 bp, encoding 381 amino acids. Transgenic plants with CoGA20ox1 had a taller phenotype; a seed enlargement phenotype; promoted SCWs deposition, leaf enlargement, and early flowering; and reduced chlorophyll and anthocyanin accumulation. Genetic analysis showed that the mutant ga20ox1-3 Arabidopsis partially rescued the phenotype of CoGA20ox1 overexpression plants. The results showed that CoGA20ox1 participates in the growth and development of C. oleifera. The morphological changes in CoGA20ox1 overexpressed plants provide a theoretical basis for further exploration of GA biosynthesis and analysis of the molecular mechanism in C. oleifera."
Authors: Shubham Temgire, Anis Ahmad Mirza, Abdul Waheed Wani, Kondle Ravi, Pratik Tanpure and Suprikesh Kadlag.
Annals of Phytomedicine (2023)
Abstract: "In warm climates, 'Crimson Seedless' may fail to develop an appropriate red colour, despite being a high-quality, red table grape (Vitis vinifera L.). Green berries also persist in most bunches even when the rest of the bunch has turned red. The plant hormone abscisic acid (ABA) is involved in the accumulation of anthocyanins in grape berry skin during maturation. Temperature increases are negatively affecting anthocyanin biosynthesis and other fruit quality characteristics in warmer regions of the world, making high-quality table grapes challenging to cultivate. Crop productivity and sustainability can be improved with nanotechnology. Table grapes are marketed based on their red colour, which is one of the most significant criteria for fruit quality. Several chemicals and practices were evaluated in this review to determine their effect on the bunch colour and metabolic profile of the grapevine variety, Crimson Seedless."
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Authors: Zhichao Sun, Xinmiao Guo, R.M. Saravana Kumar, Chunying Huang, Yan Xie, Meng Li and Jisheng Li.
Plant Science (2024)
Highlights: • Late stage of mulberry fruit ripening witnessed ethylene accumulation and physiological changes. • Late stage fruit ripening-specific differentially expressed genes and associated metabolic pathways highlighted. • Transcriptome and metabolome data interconnects ethylene signaling and mulberry fruit ripening. • MaERF3 are important for ripening process.
Abstract: "Mulberry (Morus alba L.) is a climacteric and highly perishable fruit. Ethylene has been considered to be an important trigger of fruit ripening process. However, the role of ethylene in the mulberry fruit ripening process remains unclear. In this study, we performed a comprehensive analysis of metabolomic and transcriptomic data of mulberry fruit and the physiological changes accompanying the fruit ripening process. Our study revealed that changes in the accumulation of specific metabolites at different stages of fruit development and ripening were closely correlated to transcriptional changes as well as underlying physiological changes and the development of taste biomolecules. The ripening of mulberry fruits was highly associated with the production of endogenous ethylene, and further application of exogenous ethylene assisted the ripening process. Transcriptomic analysis revealed that differential expression of diverse ripening-related genes was involved in sugar metabolism, anthocyanin biosynthesis, and cell wall modification pathways. Network analysis of transcriptomics and metabolomics data revealed that many transcription factors and ripening-related genes were involved, among which ethylene-responsive transcription factor 3 (MaERF3) plays a crucial role in the ripening process. The role of MaERF3 in ripening was experimentally proven in a transient overexpression assay in apples. Our study indicates that ethylene plays a vital role in modulating mulberry fruit ripening. The results provide a basis for guiding the genetic manipulation of mulberry fruits towards sustainable agricultural practices and improve post-harvest management, potentially enhancing the quality and shelf life of mulberry fruits for sustainable agriculture and forestry."
Authors: Mingkun Chen, Xiaoyun Cao, Yuanxing Huang, Wenting Zou, Xiaolong Liang, Yue Yang, Yu Wang, Jun Wei and Houhua Li.
Plant Science (2024)
Highlights • The key factors affecting the color change of Malus ‘Pinkspire’ fruits were investigated using the periods of significant color changes during fruit ripening. • MpbZIP9 can directly bind the promoter of MpF3’H and significantly activate MpF3’H expression. • MpbZIP9 transcription factor can regulate the synthesis of peel anthocyanin, which a positive regulator.
Abstract: "Malus ‘Pinkspire’ is regulated by abscisic acid (ABA), which results in a red colour, but the regulatory relationship between ABA and anthocyanin synthesis has not been determined. The key factors affecting the colour change of M. ‘Pinkspire’ peel were investigated during the periods of significant colour changes during fruit ripening. The results showed that the transcription factor MpbZIP9 associated with ABA was screened by transcriptomic analysis. MpbZIP9 expression was consistent with the trend of structural genes expression for anthocyanin synthesis in the peel during fruit ripening, as well as with changes in the content of ABA, which is a positive regulator. A yeast one-hybrid assay showed that MpbZIP9 can directly bind to the promoter of MpF3’H. Dual luciferase reporter gene assays and GUS staining experiments showed that MpbZIP9 significantly activate MpF3’H expression. In addition, overexpression of the MpbZIP9 significantly enhanced anthocyanin accumulation and the expression of genes involved in anthocyanin synthesis. In contrast, virus-induced silencing of the MpbZIP9 significantly reduced the expression of structural genes involved in anthocyanin synthesis. These results suggest that the MpbZIP9 transcription factor can regulate the synthesis of peel anthocyanin and is a positive regulator that promotes anthocyanin biosynthesis by activating MpF3’H expression."
Authors: Xi Zhang, Lujia Yu, Mengjiao Zhang, Ting Wu, Tingting Song, Yuncong Yao, Jie Zhang and Ji Tian.
The Plant Journal (2024)
Significance Statement: Our findings validate a role for the MdERF109-MdWER-MdJAZ2 module in anthocyanin biosynthesis and uncover a novel mechanism for how light and MeJA signals are coordinated anthocyanin biosynthesis in apple fruit.
Abstract: "Anthocyanin generation in apples (Malus domestica) and the pigmentation that results from it may be caused by irradiation and through administration of methyl jasmonate (MeJA). However, their regulatory interrelationships associated with fruit coloration are not well defined. To determine whether MdERF109, a transcription factor (TF) involved in light-mediated coloration and anthocyanin biosynthesis, has synergistic effects with other proteins, we performed a yeast two-hybrid assessment and identified another TF, MdWER. MdWER was induced by MeJA treatment, and although overexpression of MdWER alone did not promote anthocyanin accumulation co-overexpression with MdERF109 resulted in significantly increase in anthocyanin biosynthesis. MdWER may form a protein complex with MdERF109 to promote anthocyanin accumulation by enhancing combinations between the proteins and their corresponding genes. In addition, MdWER, as a MeJA responsive protein, interacts with the anthocyanin repressor MdJAZ2. Transient co-expression in apple fruit and protein interaction assays allowed us to conclude that MdERF109 and MdJAZ2 interact with MdWER and take part in the production of anthocyanins upon MeJA treatment and irradiation. Our findings validate a role for the MdERF109-MdWER-MdJAZ2 module in anthocyanin biosynthesis and uncover a novel mechanism for how light and MeJA signals are coordinated anthocyanin biosynthesis in apple fruit."
Authors: Shuihuan Guo, Meng Zhang, Mingxin Feng, Guipeng Liu, Laurent Torregrosa, Xiaoqing Tao, Ruihua Ren, Yulin Fang, Zhenwen Zhang, Jiangfei Meng and Tengfei Xu.
Horticulture Research (2024)
Abstract: "Anthocyanins are the primary color components of grapevine berries and wines. In cultivation practices, a moderate water deficit can promote anthocyanin accumulation in red grape skins. Our previous study showed that ABA plays a key role in this process. Herein, we identified a microRNA, vv-miR156b, that is generated in grapevine berries in response to drought stress, along with increasing anthocyanin content and biosynthetic structural gene transcripts. In contrast, the vv-miR156b short tandem target mimic (STTM) function-loss callus exhibits the opposite phenotype. Results from the in vivo and in vitro experiments revealed that the abscisic acid (ABA) signaling regulated transcription factor VvAREB2 binds directly to the ABA responsive element (ABRE) of the MIR156b promoter and activates miR156b expression. Furthermore, two miR156b downstream targets, VvSBP8 and VvSBP13, exhibited reducing grape anthocyanin content in their overexpressors and contrary resulted showed in their CRISPR-edited lines, the decrease of anthocyanin content was rescued in miR156b and SBP8/13 double overexpressors. We further demonstrated that both VvSBP8 and VvSBP13 encoding transcriptional repressors displayed sufficient ability to interact with VvMYC1 and VvMYBA1, thereby interfering with MYB–bHLH–WD (MBW) repeat transcriptional complex formation, resulting in the repression of anthocyanin biosynthesis. Our findings demonstrate a direct functional relationship between ABA signaling and the miR156-SBP-MBW complex regulatory module in driving drought-induced anthocyanin accumulation in grape berries."
Authors: Qiu Yang, Yong Wang, Guilan Zhang, Yunxing Wang, Jingyong Huang, Youwei Feng, Yan Li, Jun Jiang and Yanjie Zhang.
Plant Science (2024)
Highlights • Overexpression of a BR inactivating enzyme gene GhPAG1 severely retarded eggplant growth and development. • BR deficiency impacts eggplant fruit development and anthocyanin coloration mainly by altering endogenous hormone homeostasis. • It was suggested that BR probably regulates eggplant fruit development and anthocyanin coloration via auxin and jasmonic acid signaling pathway, respectively.
Abstract: "Brassinosteroids (BRs) function importantly in plant growth and development, but the roles in regulating fruit development and anthocyanin pigmentation remain unclear. Eggplant (Solanum melongena L.) is an important Solanaceae vegetable crop rich in anthocyanins. The fruit size and coloration are important agronomic traits for eggplant breeding. In this study, transgenic eggplant exhibiting endogenous BRs deficiency was created by overexpressing a heterologous BRs-inactivating enzyme gene GhPAG1 driven by CaMV 35 S promoter. 35 S::GhPAG1 eggplant exhibited severe dwarfism, reduced fruit size, and less anthocyanin accumulation. Microscopic observation showed that the cell size of 35 S::GhPAG1 eggplant was significantly reduced compared to WT. Furthermore, the levels of IAA, ME-IAA, and active JAs (JA, JA-ILE, and H2JA) all decreased in 35 S::GhPAG1 eggplant fruit. RNA-Seq analyses showed a decrease in the expression of genes involved in cell elongation, auxin signaling, and JA signaling. Besides, overexpression of GhPAG1 significantly downregulated anthocyanin biosynthetic genes and associated transcription regulators. Altogether, these results strongly suggest that endogenous brassinosteroid deficiency arising from GhPAG1 overexpression impacts eggplant fruit development and anthocyanin coloration mainly by altering hormone homeostasis."
Authors: Guangyan Yang, Manyi Sun, Lester Brewer, Zikai Tang, Niels Nieuwenhuizen, Janine Cooney, Shaozhuo Xu, Jiawen Sheng, Christelle Andre, Cheng Xue, Ria Rebstock, Bo Yang, Wenjing Chang, Yueyuan Liu, Jiaming Li, Runze Wang, Mengfan Qin, Cyril Brendolise, Andrew C. Allan, Richard V. Espley, Kui Lin-Wang and Jun Wu.
Plant Biotechnology Journal (2024)
Abstract: "Variation in anthocyanin biosynthesis in pear fruit provides genetic germplasm resources for breeding, while dwarfing is an important agronomic trait, which is beneficial to reduce the management costs and allow for the implementation of high-density cultivation. Here, we combined bulked segregant analysis (BSA), quantitative trait loci (QTL), and structural variation (SV) analysis to identify a 14-bp deletion which caused a frame shift mutation and resulted in the premature translation termination of a B-box (BBX) family of zinc transcription factor, PyBBX24, and its allelic variation termed PyBBX24ΔN14. PyBBX24ΔN14 overexpression promotes anthocyanin biosynthesis in pear, strawberry, Arabidopsis, tobacco, and tomato, while that of PyBBX24 did not. PyBBX24ΔN14 directly activates the transcription of PyUFGT and PyMYB10 through interaction with PyHY5. Moreover, stable overexpression of PyBBX24ΔN14 exhibits a dwarfing phenotype in Arabidopsis, tobacco, and tomato plants. PyBBX24ΔN14 can activate the expression of PyGA2ox8 via directly binding to its promoter, thereby deactivating bioactive GAs and reducing the plant height. However, the nuclear localization signal (NLS) and Valine-Proline (VP) motifs in the C-terminus of PyBBX24 reverse these effects. Interestingly, mutations leading to premature termination of PyBBX24 were also identified in red sports of un-related European pear varieties. We conclude that mutations in PyBBX24 gene link both an increase in pigmentation and a decrease in plant height."
Authors: Linhui Zhu, Yuwu Liao, Kai Lin, Wenfei Wu, Lanjuan Duan, Pan Wang, Xian Xiao, Tingting Zhang, Xin Chen, Jianzhong Wang, Kaiqin Ye, Hao Hu, Zeng-Fu Xu and Jun Ni.
Tree Physiology (2024)
Abstract: "Anthocyanins are flavonoid-like substances that play important roles in plants in adaptation to various environmental stresses. In this research, we discovered that cytokinin (CK) alone could effectively induce the anthocyanin biosynthesis in Eucalyptus and many other perennial woody plant species, but not in tobacco and Arabidopsis, suggesting a diverse role of CK in regulating anthocyanin biosynthesis in different species. Transcriptomic and metabolomic strategies were used to further clarify the specific role of CK in regulating anthocyanin biosynthesis in Eucalyptus. The results showed that 801 and 2241 genes were differentially regulated at 6 and 24 h, respectively, after CK treatment. Pathway analysis showed that most of the differentially expressed genes were categorized into pathways related to cellular metabolism or transport of metabolites, including amino acids and sugars. The metabolomic results well supported the transcriptome data, which showed that most of the differentially regulated metabolites were related to the metabolism of sugar, amino acids, and flavonoids. Moreover, CK treatment significantly induced the accumulation of sucrose in the CK-treated leaves, while sugar starvation mimicked by either defoliation or shading treatment of the basal leaves significantly reduced the sugar increase of the CK-treated leaves, and thus inhibited CK-induced anthocyanin biosynthesis. The results of in vitro experiment also suggested that CK-induced anthocyanin in Eucalyptus was sugar-dependent. Furthermore, we identified an early CK-responsive transcription factor MYB113 in Eucalyptus, the expression of which was significantly upregulated by CK treatment in Eucalyptus but inhibited in Arabidopsis. Importantly, overexpression of EgrMYB113 in the Eucalyptus hairy roots was associated with significant anthocyanin accumulation, and upregulation of most of the anthocyanin biosynthetic genes. In conclusion, our study demonstrates a key role of CK in the regulation of anthocyanin biosynthesis in Eucalyptus, providing a molecular basis for further understanding the regulatory mechanism, and diversity of hormone-regulated anthocyanin biosynthesis in different plant species."
Authors: Maria C. Camarero, Beatriz Briegas, Jorge Corbacho, Juana Labrador and Maria C. Gomez-Jimenez.
Plants (2023)
Abstract: "The cultivated olive (Olea europaea L. subsp. europaea var. europaea) is one of the most valuable fruit trees worldwide. However, the hormonal mechanisms underlying the fruit growth and ripening in olives remain largely uncharacterized. In this study, we investigated the physiological and hormonal changes, by ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS), as well as the expression patterns of hormone-related genes, using quantitative real-time PCR (qRT-PCR) analysis, during fruit growth and ripening in two olive cultivars, ‘Arbequina’ and ‘Picual’, with contrasting fruit size and shape as well as fruit ripening duration. Hormonal profiling revealed that olive fruit growth involves a lowering of auxin (IAA), cytokinin (CKs), and jasmonic acid (JA) levels as well as a rise in salicylic acid (SA) levels from the endocarp lignification to the onset of fruit ripening in both cultivars. During olive fruit ripening, both abscisic acid (ABA) and anthocyanin levels rose, while JA levels fell, and SA levels showed no significant changes in either cultivar. By contrast, differential accumulation patterns of gibberellins (GAs) were found between the two cultivars during olive fruit growth and ripening. GA1 was not detected at either stage of fruit development in ‘Arbequina’, revealing a specific association between the GA1 and ‘Picual’, the cultivar with large sized, elongated, and fast-ripening fruit. Moreover, ABA may play a central role in regulating olive fruit ripening through transcriptional regulation of key ABA metabolism genes, whereas the IAA, CK, and GA levels and/or responsiveness differ between olive cultivars during olive fruit ripening. Taken together, the results indicate that the relative absence or presence of endogenous GA1 is associated with differences in fruit morphology and size as well as in the ripening duration in olives. Such detailed knowledge may be of help to design new strategies for effective manipulation of olive fruit size as well as ripening duration."
Authors: Shaohang Li, Yanxiao Dong, Dalu Li, Suli Shi, Na Zhao, Jielei Liao, Yang Liu and Huoying Chen.
Plant Physiology (2023)
Abstract: "Low light conditions severely suppress anthocyanin synthesis in fruit skins, leading to compromised fruit quality in eggplant (Solanum melongena L.) production. In this study, we found that exogenous methyl-jasmonate (MeJA) application can effectively rescue the poor coloration of the eggplant pericarp under low light conditions. However, the regulatory relationship between jasmonate and light signaling for regulating anthocyanin synthesis remains unclear. Here, we identified a JA-response factor, SmMYB5, as an anthocyanin positive regulator by applying RNA-sequencing, and characterization of transgenic plants. Firstly, we resolved that SmMYB5 can interact with TRANSPARENT TESTA8 (SmTT8), an anthocyanin-promoted BASIC HELIX-LOOP-HELIX (bHLH) transcription factor, to form the SmMYB5-SmTT8 complex and activate CHALCONE SYNTHASE (SmCHS), FLAVANONE-3-HYDROXYLASE (SmF3H) and ANTHOCYANIN SYNTHASE (SmANS) promoters by direct binding. Secondly, we revealed that JA signaling repressors JASMONATE ZIM DOMAIN5 (SmJAZ5) and SmJAZ10 can interfere with the stability and transcriptional activity of SmMYB5-SmTT8 by interacting with SmMYB5. JA can partially rescue the transcriptional activation of SmF3H and SmANS promoters by inducing SmJAZ5/10 degradation. Thirdly, we demonstrated that the protein abundance of SmMYB5 is regulated by light. CONSTITUTIVELY PHOTOMORPHOGENIC1 (SmCOP1) interacts with SmMYB5 to trigger SmMYB5 degradation via the 26S proteasome pathway. Finally, we delineated a light-dependent JA-SmMYB5 signaling pathway that promotes anthocyanin synthesis in eggplant fruit skins. These results provide insights into the mechanism of the integration of JA and light signals in regulating secondary metabolite synthesis in plants."
Authors: Chunxiang You, Yuepeng Han and Jianping An.
Fruit Research (2023
Abstract: "Gibberellin (GA) inhibits anthocyanin biosynthesis, but the mechanism by which GA regulates anthocyanin accumulation is still not fully understood. Teosinte branched1/cycloidea/proliferating (TCP) transcription factor MdTCP46 is a positive regulator of anthocyanin biosynthesis in apple, which acts by recruiting MdMYB1, a core anthocyanin regulator, and activating its transcriptional activity. In this study, we found that MdTCP46 was responsive to the GA signaling at the transcriptional level. GA treatment inhibited the transcription of MdTCP46, while the expression of the MdTCP46 promoter was induced by paclobutrazol (PAC), an inhibitor of GA biosynthesis. Anthocyanin accumulation assays in apple fruits and callus showed that MdTCP46 played a negative role in GA-inhibited anthocyanin biosynthesis. Molecular biochemical assays indicated that MdTCP46 interacted with the DELLA protein MdRGL2a, a GA repressor responsible for anthocyanin biosynthesis in apple. MdRGL2a played a synergistic role in MdTCP46-promoted anthocyanin biosynthesis by enhancing the interaction between MdTCP46 and MdMYB1. Taken together, these results reveal that the RGL2a-TCP46-MYB1 module plays an important role in GA-mediated anthocyanin biosynthesis in apple. The discovery of the RGL2a-TCP46-MYB1 module is helpful to enrich the anthocyanin transcriptional regulatory network and provide reference for further study of GA signaling pathway."
Authors: Xi Wang, Zhuoyang Li, Yiting Shi, Ziyan Liu, Xiaoyan Zhang, Zhizhong Gong and Shuhua Yang.
The EMBO Journal (2023)
Synopsis: Plants respond to extreme cold stress by synthesizing strigolactones; however, how this class of plant hormones promotes freezing tolerance is still poorly understood. Here, cold-induced strigolactones are shown to promote plant survival in sub-zero temperatures by enhancing expression of freezing tolerance regulators DREB1/CBF. Strigolactones positively regulate plant freezing tolerance via a CBF-dependent pathway. The E3 ligase MAX2 interacts with and ubiquitinates the transcription factor WRKY41, mediating its cold-induced degradation. WRKY41 represses the cold-induced expression of CBFs by directly binding to their promoters. SLs-mediated degradation of SMXLs also contributes to enhanced freezing tolerance by accumulating anthocyanin.
Abstract: "Cold stress is a major abiotic stress that adversely affects plant growth and crop productivity. The C-REPEAT BINDING FACTOR/DRE BINDING FACTOR 1 (CBF/DREB1) transcriptional regulatory cascade plays a key role in regulating cold acclimation and freezing tolerance in Arabidopsis (Arabidopsis thaliana). Here, we show that max (more axillary growth) mutants deficient in strigolactone biosynthesis and signaling display hypersensitivity to freezing stress. Exogenous application of GR245DS, a strigolactone analog, enhances freezing tolerance in wild-type plants and strigolactone-deficient mutants and promotes the cold-induced expression of CBF genes. Biochemical analysis showed that the transcription factor WRKY41 serves as a substrate for the F-box E3 ligase MAX2. WRKY41 directly binds to the W-box in the promoters of CBF genes and represses their expression, negatively regulating cold acclimation and freezing tolerance. MAX2 ubiquitinates WRKY41, thus marking it for cold-induced degradation and thereby alleviating the repression of CBF expression. In addition, SL-mediated degradation of SMXLs also contributes to enhanced plant freezing tolerance by promoting anthocyanin biosynthesis. Taken together, our study reveals the molecular mechanism underlying strigolactones promote the cold stress response in Arabidopsis."
Authors: Richard V. Espley and Laura Jaakola.
Plant, Cell & Environment (2023)
Abstract: "For many fruit crops, the colour of the fruit outwardly defines its eating quality. Fruit pigments provide reproductive advantage for the plant as well as providing protection against unfavourable environmental conditions and pathogens. For consumers these colours are considered attractive and provide many of the dietary benefits derived from fruits. In the majority of species, the main pigments are either carotenoids and/or anthocyanins. They are produced in the fruit as part of the ripening process, orchestrated by phytohormones and an ensuing transcriptional cascade, culminating in pigment biosynthesis. Whilst this is a controlled developmental process, the production of pigments is also attuned to environmental conditions such as light quantity and quality, availability of water and ambient temperature. If these factors intensify to stress levels, fruit tissues respond by increasing (or ceasing) pigment production. In many cases, if the stress is not severe, this can have a positive outcome for fruit quality. Here, we focus on the principal environmental factors (light, temperature and water) that can influence fruit colour."
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