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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: 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: Xiao Han, Mengyi Kui, Tingting Xu, Jingwen Ye, Jiancan Du, Milian Yang, Yanjuan Jiang and Yanru Hu.
The Plant Cell (2023)
Abstract: "CONSTANS (CO) is a master flowering-time regulator that integrates photoperiodic and circadian signals in Arabidopsis thaliana. CO is expressed in multiple tissues, including young leaves and seedling roots, but little is known about the roles and underlying mechanisms of CO in mediating physiological responses other than flowering. Here, we show that CO expression is responsive to jasmonate. CO negatively modulated jasmonate-imposed root growth inhibition and anthocyanin accumulation. Seedlings from co mutants were more sensitive to jasmonate, whereas overexpression of CO resulted in plants with reduced sensitivity to jasmonate. Moreover, CO mediated the diurnal gating of several jasmonate-responsive genes under long-day conditions. We demonstrate that CO interacts with JASMONATE ZIM-DOMAIN (JAZ) repressors of jasmonate signaling. Genetic analyses indicated that CO functions in a CORONATINE-INSENSITIVE1 (COI1)-dependent manner to modulate jasmonate responses. Furthermore, CO physically associated with the basic helix-loop-helix (bHLH) subgroup IIId transcription factors bHLH3 and bHLH17. CO acted cooperatively with bHLH17 in suppressing jasmonate signaling, but JAZ proteins interfered with their transcriptional functions and physical interaction. Collectively, our results reveal the crucial regulatory effects of CO on mediating jasmonate responses, and explain the mechanism by which CO works together with JAZ and bHLH subgroup IIId factors to fine-tune jasmonate signaling."
Authors: Susheng Song, Bei Liu, Junqiao Song, Shihai Pang, Tianxue Song, Shang Gao, Yue Zhang, Huang Huang and Tiancong Qi.
Journal of Integrative Plant Biology (2022)
Abstract: "The phytohormones ethylene (ET) and jasmonate (JA) regulate plant development, growth, and defense responses; however, the molecular basis for their signaling crosstalk is unclear. Here, we show that JA-ZIM-domain (JAZ) proteins, which repress JA signaling, repress trichome initiation/branching and anthocyanin accumulation, and inhibit the transcriptional activity of the bHLH-MYB members (GL3-GL1 and TT8-MYB75) of WD-repeat/bHLH/MYB (WBM) complexes. The ET-stabilized transcription factors ETHYLENE-INSENSITIVE3 (EIN3) and EIN3-LIKE1 (EIL1) were found to bind to several members of WBM complexes, including GL3, EGL3, TT8, GL1, MYB75, and TTG1. This binding repressed the transcriptional activity of the bHLH-MYB proteins and inhibited anthocyanin accumulation, trichome formation, and defenses against insect herbivores while promoting root hair formation. Conversely, the JA-activated bHLH members GL3, EGL3, and TT8 of WBM complexes were able to interact with and attenuate the transcriptional activity of EIN3/EIL1 at the HOOKLESS1 promoter, and their overexpression inhibited apical hook formation. Thus, this study demonstrates a molecular framework for signaling crosstalk between JA and ET in plant development, secondary metabolism, and defense responses."
Authors: Andrea Chini, Isabel Monte, Gemma Fernández-Barbero, Marta Boter, Glenn Hicks, Natasha Raikhel and Roberto Solano.
Plant Physiology (2021)
Abstract: "The phytohormone JA-Ile regulates many stress responses and developmental processes in plants. A co-receptor complex formed by the F-box protein COI1 (Coronatine Insensitive 1) and a JAZ (Jasmonate ZIM-domain) repressor perceives the hormone. JA-Ile antagonists are invaluable tools for exploring the role of JA-Ile in specific tissues and developmental stages, and for identifying regulatory processes of the signalling pathway. Using two complementary chemical screens, we identified three compounds that exhibit a robust inhibitory effect on both the hormone-mediated COI-JAZ interaction and degradation of JAZ1 and JAZ9 in vivo. One molecule, J4, also restrains specific JA-induced physiological responses in different angiosperm plants, including JA-mediated gene expression, growth inhibition, chlorophyll degradation and anthocyanin accumulation. Interaction experiments with purified proteins indicate that J4 directly interferes with the formation of the Arabidopsis (Arabidopsis thaliana) COI1-JAZ complex otherwise induced by JA. The antagonistic effect of J4 on COI1-JAZ also occurs in the liverwort Marchantia polymorpha, suggesting the mode of action is conserved in land plants. Besides JA signalling, J4 works as an antagonist of the closely-related auxin signalling pathway, preventing TIR1/Aux-IAA interaction and auxin responses in planta, including hormone-mediated degradation of an auxin repressor, gene expression and gravitropic response. However, J4 does not affect other hormonal pathways. Altogether, our results show that this dual antagonist competes with JA-Ile and auxin, preventing the formation of phylogenetically related receptor complexes. J4 may be a useful tool to dissect both the JA-Ile and auxin pathways in particular tissues and developmental stages since it reversibly inhibits these pathways."
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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: Andreas S. Richter, Thomas Nägele, Bernhard Grimm, Kerstin Kaufmann, Michael Schroda, Dario Leister and Tatjana Kleine.
Plant Communications (2023)
Abstract: "Plastids communicate their developmental and physiological status to the nucleus via retrograde signaling, thus allowing nuclear gene expression to be adjusted appropriately. Signaling during plastid biogenesis and responses of mature chloroplasts to environmental changes are designated as ‘biogenic’ and ‘operational’ controls, respectively. A prominent example of the investigation of biogenic signaling is the screen for gun (genomes uncoupled) mutants. Although the first five gun mutants were identified 30 years ago, the functions of GUN proteins in retrograde signaling remain controversial and that of GUN1 is hotly disputed. Here, we provide background information and critically discuss recently proposed concepts that address GUN-related signaling and some novel gun mutants. Moreover, considering heme as a candidate in retrograde signaling, we revisit the spatial organization of heme biosynthesis and export from plastids. Although this review focuses on GUN pathways, we also highlight recent progress in the identification and elucidation of chloroplast-derived signals that regulate the acclimation response in green algae and plants. Here, stress-induced accumulation of unfolded/misassembled chloroplast proteins evokes a chloroplast-specific unfolded protein response (cpUPR), which leads to changes in the expression levels of nucleus-encoded chaperones and proteases to restore plastid protein homeostasis. We also address the importance of chloroplast-derived signals for activation of flavonoid biosynthesis leading to the production of anthocyanins during stress acclimation through sucrose non-fermenting-1-related protein kinase-1 (SnRK1). Finally, a framework for the identification and quantification of intercompartmental signaling cascades at the proteomic and metabolomic levels is provided, and we discuss future directions in the dissection of organelle-nucleus communication."
Authors: Galileo Estopare Araguirang and Andreas S. Richter.
New Phytologist (2022)
Abstract: "Due to their sessile nature, plants cannot escape adverse environmental conditions and evolved mechanisms to cope with sudden environmental changes. The reaction to variations in abiotic factors, also summarized as acclimation response, affects all layers of cellular functions and involves rapid modification of enzymatic activities, the metabolome, proteome and transcriptome on different timescales. One trait of plants acclimating to high light (HL) is the rapid transcriptional activation of the flavonoid biosynthesis (FB) pathway resulting in the accumulation of photoprotective and antioxidative flavonoids, such as flavonols and anthocyanins, in the leaf tissue. Although enormous progress has been made in identifying enzymes and transcriptional regulators of FB by forward and reverse genetic approaches in the past, the signals and signalling pathways permitting the conditional activation of FB in HL are still debated. With this Tansley Insight, we summarize the current knowledge on the proposed signals and downstream factors involved in regulating FB and will discuss their contribution to, particularly, HL-induced accumulation of anthocyanins."
Authors: Peian Zhang, Qianqian Zuo, Huanchun Jin, Tariq Pervaiz, Tianyu Dong, Dan Pei, Yanhua Ren, Haifeng Jia and Jingggui Fang.
Scientia Horticulturae (2022)
Highlights: • VvSnRK2.2 and VvSnRK2.7 promoted the berry ripening process on a molecular and physiological level. • VvSnRK2.3 and VvSnRK2.6 induced high resistance of fruits to Botrytis cinerea. • VvSnRK2 family genes were studied systematically.
Abstract: "Even though abscisic acid (ABA) plays a significant role in fruit growth and responses to a variety of environmental stimuli, the signaling mechanisms that underpin these activities are unknown. role. In present study, we identified seven sucrose non-fermenting-1-related protein kinases 2 (SnRK2s) from the grape (Vitis vinifera L.) genome, which may localized in the nucleus, membrane, and cytoplasm. The overexpression (OE) of VvSnRK2s showed that VvSnRK2.2 and VvSnRK2.7 promoted the ripening process in strawberries on molecular and physiological levels (fruit weight, berry firmness, cell wall composition, total soluble sugar, titratable acid, pigments, phenolic compounds), furthermore, VvSnRK2.3 and VvSnRK2.6 induced strong resistance in strawberry fruits to B. cinerea. Only VvSnRK2.2 and VvSnRK2.7 were found to interact with VvMYB24, a positive regulator of grape berry ripening. Additionally, VvSnRK2s interact with VvABF1 (an ABA-responsive factor) and VvABI1 (ABA insensitive 1) to mediate the ABA signalling pathway. VvSnRK2s respond to different hormonal treatments and abiotic stresses to improve plant stress resistance. Collectively, our results demonstrated that VvSnRK2.2 and VvSnRK2.7 are positive regulators grape berry development and ripening, while, VvSnRK2.3 and VvSnRK2.6 mediate grape resistance against B. cinerea."
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