How Cold-Responsive Factors Help Citrus Fruits Produce More Colorful Pigments

Greg Howard
26th June, 2024

How Cold-Responsive Factors Help Citrus Fruits Produce More Colorful Pigments

Image Source: Natural Science News, 2024

Key Findings

  • The study from Zhejiang University focused on how low temperature (LT) promotes anthocyanin production in blood oranges
  • Researchers identified two key proteins, CsERF054 and CsERF061, that activate the gene CsRuby1, which is crucial for anthocyanin biosynthesis
  • CsERF061 also forms a protein complex with CsRuby1 to further enhance the production of anthocyanins, revealing a dual regulatory mechanism
Anthocyanins are natural pigments and dietary antioxidants that serve multiple biological roles in plants and are crucial for animal and human nutrition. Low temperature (LT) has been known to promote anthocyanin biosynthesis in various species, including blood orange. A key player in this process is a retrotransposon in the promoter of Ruby1, which encodes an R2R3 MYB transcription factor responsible for cold-induced anthocyanin accumulation in blood orange flesh. However, the specific mechanism behind this phenomenon has remained unclear. A recent study from Zhejiang University aimed to shed light on this mechanism by characterizing two LT-induced ETHYLENE RESPONSE FACTORS (CsERF054 and CsERF061)[1]. The study found that both CsERF054 and CsERF061 can activate the expression of CsRuby1 by directly binding to a DRE/CRT cis-element within the retrotransposon in the promoter of CsRuby1. This binding positively regulates anthocyanin biosynthesis. Furthermore, it was discovered that CsERF061 also forms a protein complex with CsRuby1 to co-activate the expression of anthocyanin biosynthetic genes, providing a dual mechanism for the upregulation of the anthocyanin pathway. The findings from this study are significant as they provide insights into how LT mediates anthocyanin biosynthesis, thereby increasing our understanding of the regulatory network of anthocyanin biosynthesis in blood orange. This research ties together previous findings on the role of transcription factors in anthocyanin biosynthesis. For instance, in red-skinned pears, the MYB-bHLH-WDR complex is known to play a critical role in the transcriptional regulation of light-induced anthocyanin biosynthesis[2]. Similarly, in apples, the interaction between MdTRB1 and MdMYB9 is essential for modulating the accumulation of anthocyanin and proanthocyanidin, with the JA signaling repressor MdJAZ1 negatively modulating this process[3]. This study from Zhejiang University expands on these earlier findings by highlighting the role of ETHYLENE RESPONSE FACTORS in the cold-induced biosynthesis of anthocyanins in blood orange. The dual mechanism involving both direct activation of CsRuby1 and the formation of a protein complex with CsRuby1 to co-activate anthocyanin biosynthetic genes adds a new layer of complexity to our understanding of how environmental factors like temperature influence anthocyanin production. In terms of methodology, the researchers employed a series of molecular biology techniques to elucidate these mechanisms. They used chromatin immunoprecipitation and electrophoretic mobility shift assays to demonstrate the binding of CsERF054 and CsERF061 to the DRE/CRT cis-element within the CsRuby1 promoter. Additionally, protein interaction assays revealed the formation of a complex between CsERF061 and CsRuby1, which was shown to co-activate anthocyanin biosynthetic genes. These insights not only deepen our understanding of plant physiology but also have practical implications. For instance, manipulating the expression of these transcription factors could potentially be used to enhance anthocyanin content in fruits, thereby improving their nutritional value and antioxidant capacity. This is particularly relevant given that dietary anthocyanins have been shown to positively impact overall antioxidant status in humans[4]. Overall, the study provides a comprehensive understanding of the regulatory mechanisms behind LT-induced anthocyanin biosynthesis in blood orange, building on previous research and offering new avenues for both scientific inquiry and practical applications in agriculture and nutrition.

GeneticsBiochemPlant Science

References

Main Study

1) The R2R3 MYB Ruby1 is activated by two cold responsive ethylene response factors, via the retrotransposon in its promoter, to positively regulate anthocyanin biosynthesis in citrus.

Published 23rd June, 2024

https://doi.org/10.1111/tpj.16866

Related Studies

2) Light-responsive transcription factor PpWRKY44 induces anthocyanin accumulation by regulating PpMYB10 expression in pear.

https://doi.org/10.1093/hr/uhac199

3) Jasmonate induces biosynthesis of anthocyanin and proanthocyanidin in apple by mediating the JAZ1-TRB1-MYB9 complex.

https://doi.org/10.1111/tpj.15245

4) Dietary flavonoid intake, total antioxidant capacity and lipid oxidative damage: A cross-sectional study of Iranian women.

https://doi.org/10.1016/j.nut.2015.11.011


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