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Authors: Marieke Dubois
Plant Physiology (2024)
Excerpt: "Altogether, the work performed by Mohorović and colleagues revealed the chronology of ethylene-mediated photosynthesis inhibition in young tomato leaves. Their approach defined a three-step response consisting of: (1) a reduction in the capture of CO2 and light, resulting in a rapid decline of soluble sugars, (2) a transcriptional down-regulation of genes related to photosynthesis, coupled to the up-regulation of genes necessary to gather energy from other sources, perhaps sucrose or proteins and (3) a long-term starch and chlorophyll breakdown resulting in leaf senescence (Figure 1D). Adding a time-factor to the extensively studied ethylene response is crucial, as hormones often affect temporary or dynamic processes (Waadt et al., 2022) that can only be detected by time-course experiments, as was elegantly performed in Mohorović et al., 2023. This work paves the way towards further molecular characterization of the regulatory cascades linking the different steps of the ethylene-mediated inhibition of photosynthesis."
Authors: Yanna Xu, Congjun You, Changbin Xu, Chaofan Zhang, Xiaoli Hu, Xiaolong Li, Haijie Ma, Jinli Gong and Xuepeng Sun.
Postharvest Biology and Technology (2024)
Highlights: • Skin coloration of tomato fruit responds differentially to red and blue light. • Both lights promote biosynthesis of carotenoids and phytohormones. • Gene modules associated with carotenoid and hormone metabolism were identified. • Transcription factors as key regulators of the modules were uncovered. • A working model was proposed to depict the light regulation of fruit coloration.
Abstract: "Understanding how light regulates pigment composition and accumulation is crucial for postharvest management of fruit quality and nutritional value. In this study, we investigated the influence of light quality, specifically the blue and red lights, on coloration of tomato fruit. We show that both lights expedite the progress of skin coloration in tomato fruit by promoting chlorophyll degradation, stimulating carotenoid biosynthesis, accelerating plastid conversion, and enhancing plant hormone (i.e., abscisic acid and ethylene) biosynthesis. However, red light shows higher efficiency in inducing color transition compared with blue light. Gene expression network analysis unraveled several modules that are associated with carotenoid metabolism and hormone biosynthesis in response to light treatments, among which the transcription factors including WRKY20, MYB12, ARR11, NAC16, bHLH46, ZNF69, and MYB58 were identified as potential key regulators. Collectively, our data provide new threads on the regulation of fruit coloration by light quality and highlight the potential utility of red LED treatment to improve the color and quality of tomato fruit."
Authors: Marta Pujol and Jordi Garcia-Mas.
Journal of Experimental Botany (2023)
Abstract: "Fruit ripening is a complex and highly regulated process where tomato and strawberry have been the model species classically used for studying climacteric and non-climacteric fleshy fruit ripening types, respectively. Melon has emerged as an alternative ripening model because climacteric and non-climacteric cultivars exist, which makes it possible to dissect the regulation of ripening using a genetic approach. Several QTLs that regulate climacteric fruit ripening have been identified to date, and their combination in both climacteric and non-climacteric genetic backgrounds resulted in lines with different ripening behaviors, demonstrating that the climacteric intensity can be genetically modulated. The review discusses our current knowledge of the physiological changes observed during melon climacteric fruit ripening as ethylene production, fruit abscission, chlorophyll degradation, firmness and aroma, as well as their complex genetic control. From pioneer experiments in which ethylene biosynthesis was silenced, to the recent genetic edition of ripening regulators, current data suggest that the climacteric response is determined by the interaction of several loci under quantitative inheritance. The exploitation of the rich genetic diversity of melon will enable the discovery of additional genes involved in the regulation of the climacteric response, ultimately leading to breeding aromatic melon fruits with extended shelf life."
Authors: Ming Zeng, Nicole M. van Dam and Bettina Hause.
Physiologia Plantarum (2023)
Abstract: "Ethylene (ET) controls many facets of plant growth and development under abiotic and biotic stresses. MtEIN2, as a critical element of the ET signalling pathway, is essential in biotic interactions. However, the role of MtEIN2 in responding to abiotic stress, such as combined nutrient deficiency, is less known. To assess the role of ethylene signalling in nutrient uptake, we manipulated nitrate (NO3-) and phosphate (Pi) availability for wild type (WT) and the ethylene-insensitive (MtEIN2-defective) mutant, sickle, in Medicago truncatula. We measured leaf biomass and photosynthetic pigments in WT and sickle to identify conditions leading to different responses in both genotypes. Under combined NO3- and Pi deficiency, sickle plants had higher chlorophyll and carotenoid contents than WT plants. Under these conditions, nitrate content and gene expression levels of nitrate transporters were higher in the sickle mutant than in the WT. This led to the conclusion that MtEIN2 is associated with nitrate uptake and the content of photosynthetic pigments under combined Pi and NO3-deficiency in M. truncatula. We conclude that ethylene perception plays a critical role in regulating the nutrient status of plants."
Via Jean-Michel Ané
Authors: Zhiqian Li, Jingwen Li, Xia Ye, Xianbo Zheng, Bin Tan, Jidong Li, Jun Cheng, Wei Wang, Langlang Zhang, Xiaobei Wang and Jiancan Feng.
Scientia Horticulturae (2022)
Highlights • Ethylene plays important role during rachis degreening, expression of VvERF95 can be induced by ethylene. • VvERF95 upregulate VvPAO1 expression by binding to DRE cis-element in its promoter. • Transgenic plants of VvERF95 have lower chlorophyll content and transcript level of VvPAO1 and the other CCGs were increased.
Abstract: "Rachis degreening is one of the main problems during postharvest storage of grape, its regulatory mechanism remains obscure. Here, we found that production of ethylene was increased and chlorophyll content was decreased during rachis degreening of Shine Muscat grape, while the reverse were observed after 1-MCP (1-methylcyclopropene) treatment. The ethylene transcription factor VvERF95 was isolated, and its transcriptional changes were closely correlated with chlorophyll content during rachis browning. The expression of VvERF95 was induced by ethylene and inhibited by 1-MCP. Dual-luciferase, yeast one-hybrid and EMSA assays, as well as motif mutation experiments, indicated that VvERF95 can bind to the promoter of pheophorbide a oxygenase (VvPAO1) and upregulate its transcript levels. Overexpression of VvERF95 in grape lead to chlorophyll degradation in grape leaves, and increases in the transcript levels of VvPAO1 and most genes in the chlorophyll degradation pathway. Collectively, our findings decipher the mechanism of ethylene-enhanced chlorophyll degradation in grape, and will be useful for manipulating chlorophyll accumulation in grape and other plants."
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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: Gang Ma, Lancui Zhang, Kan Murakami, Masaki Yahata and Masaya Kato.
The Horticulture Journal (2023)
Abstract: ‘Miyagawa-wase’ (Citrus unshiu Marcow.), an early-season citrus variety, is rich in multiple nutrients and widely consumed in Japan. In ‘Miyagawa-wase’, when the pulp reaches maturity and is ready to eat, the peel is still a greenish color because of the relatively high temperature in the harvest season. In this study, to improve the coloration of ‘Miyagawa-wase’ peel, we treated the fruit with 1-naphthaleneacetic acid (NAA) after harvest. The results showed that postharvest treatment with NAA was effective to induce chlorophyll degradation and carotenoid accumulation in ‘Miyagawa-wase’ peel during storage. In the NAA treatment, the reduction in the chlorophyll contents after harvest was in parallel with decreases in the expression of chlorophyll biosynthetic genes (CitGGDR, CitCHLH, CitCHL27, CitPORA, and CitCAO) and an increase in chlorophyll degradation gene CitPPH. The contents of the major carotenoids, β-cryptoxanthin and 9-cis-violaxanthin, were increased by the NAA treatment through upregulation of the expression of carotenoid biosynthetic genes (CitPSY, CitPDS, CitZDS, CitLCYb2, and CitHYb) after harvest. In addition, it was found that the positive effect on degreening in the NAA treatment was inhibited by the ethylene antagonist 1-MCP. In the combination treatment using NAA and 1-MCP, the total chlorophyll content was much higher, while the contents of β-cryptoxanthin and 9-cis-violaxanthin were lower compared with NAA treatment alone, indicating that the acceleration of degreening by NAA may be caused by ethylene. The results presented in this study suggest that postharvest NAA treatment is an effective method for improving the peel coloration in early-season citrus varieties."
Authors: Hongli Li, Gangshuai Liu and Daqi Fu.
Postharvest Biology and Technology (2023)
Highlights: • Tomato serves as the model plant for studying fruit quality formation. • Fruit quality formation is regulated by a series of transcription factors. • Interactions between transcription factors related to fruit quality.
Abstract: "Tomato serves as the model plant for studying fruit ripening and quality formation including pigment, texture, flavor, aroma and nutrition. The ripening of tomato fruit results from the selective expression of ripening-related genes, which are strictly regulated by transcription factors (TFs), such as RIPENING INHIBITOR (RIN), NON-RIPENING (NOR) and COLORLESS NON-RIPENING (CNR). Understanding the transcriptional network has important biological significance for the fruit ripening regulation, which can help improve fruit quality and commodity value, and improve the utilization of agricultural resources. The molecular mechanism of TF control, a redundant regulatory network, has been extensively studied thanks to advancements in scientific research technologies. Here, we focus on the synergistic or antagonistic regulation of TFs in tomato fruit ripening, including the relationship between TFs and the regulatory patterns of ripening-related target genes, which is supported by sufficient evidence."
Authors: Wei Chen, Yuchen Zheng, Jingyi Wang, Zijing Wang, Zhen Yang, Xiaoyu Chi, Lingyan Dai, Guihua Lu, Yonghua Yang and Bo Sun.
New Phytologist (2023)
Abstract: "The onset of leaf de-greening and senescence is governed by a complex regulatory network including environmental cues and internal factors such as transcription factors (TFs) and phytohormones, in which ethylene (ET) is one key inducer. However, the detailed mechanism of ET signalling for senescence regulation is still largely unknown. Here, we found that the WRKY TF SbWRKY50 from Sorghum bicolor L., a direct target of the key component ETHYLENE INSENSITIVE3 (EIN3) in ET signalling, functioned for leaf senescence repression. The CRISPR/Cas9-edited SbWRKY50 mutant (SbWRKY5O-KO) of sorghum displayed precocious senescent phenotypes, while SbWRKY50 overexpression delayed age-dependent and dark-induced senescence in sorghum. SbWRKY50 negatively regulated chlorophyll degradation through direct binding to the promoters of several chlorophyll catabolic genes. In addition, SbWRKY50 recruited the PRC1 complex through direct interaction with SbBMI1A, to induce H2Aub accumulation on the chlorophyll catabolic genes for epigenetic silencing and thus delayed leaf senescence. Especially, SbWRKY50 can suppress early steps of chlorophyll catabolic pathway via directly repressing SbNYC1 (NON-YELLOW COLORING 1). Other senescence-related hormones could also influence leaf senescence through repression of SbWRKY50. Hence, our work shows that SbWRKY50 is an essential regulator downstream of ET and SbWRKY50 also responds to other phytohormones for senescence regulation in sorghum."
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