How WRKY75 Gene Controls Color Pigment in Young Citrus Plants

Jim Crocker
12th August, 2024

How WRKY75 Gene Controls Color Pigment in Young Citrus Plants

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Huazhong Agricultural University found that juvenile citrus tissues show temporary red coloration due to anthocyanin accumulation
  • The gene CitWRKY75 was identified as a key regulator, with its expression matching the appearance and fading of red coloration in these tissues
  • Overexpressing CitWRKY75 in tobacco plants increased anthocyanin content, confirming its role in promoting anthocyanin accumulation by activating the CitRuby1 gene
Understanding how plants regulate anthocyanin accumulation is crucial for enhancing their ornamental value, attracting pollinators, and improving their resilience to environmental stress. Anthocyanins are pigments responsible for red, purple, and blue colors in many plants. While the transcriptional regulation of anthocyanins has been widely studied, the mechanisms behind their accumulation in juvenile tissues remain less explored. Recent research conducted by Huazhong Agricultural University has shed light on this process in citrus plants[1]. The study discovered that many juvenile citrus tissues, including flowers, leaves, and pericarp, exhibit transient anthocyanin accumulation, resulting in a red coloration. Using a method called weighted gene co-expression network analysis (WGCNA), the researchers identified a candidate gene named CitWRKY75. This gene's expression levels were found to be highly consistent with the appearance and fading of the red coloration in juvenile tissues. To confirm the role of CitWRKY75, the researchers overexpressed this gene in tobacco plants, which led to a significant increase in anthocyanin content. Further experiments, including LUC and yeast one-hybrid assays, demonstrated that CitWRKY75 could bind to the promoter of another gene called CitRuby1. CitRuby1 encodes a key transcription factor that promotes anthocyanin accumulation. This finding indicates that CitWRKY75 promotes the expression of CitRuby1, thereby enhancing anthocyanin accumulation in juvenile citrus tissues. Interestingly, the study also compared the expression levels of CitWRKY75 and CitRuby1 during the later developmental stages of blood orange. The results showed that CitWRKY75 was not the main regulatory factor for anthocyanin accumulation at these later stages, suggesting its role is specific to juvenile tissues. This research builds on previous findings about the regulation of anthocyanin biosynthesis in various plants. For instance, similar regulatory mechanisms involving MYB transcription factors have been observed in petunia and Arabidopsis[2]. In petunia, the MYB27 gene acts as an anthocyanin repressor within the MYB-bHLH-WD repeat (MBW) complex, which regulates anthocyanin gene transcription[2]. Another study on pears demonstrated that light-induced anthocyanin biosynthesis involves a complex interaction between different proteins, including BBX16 and HY5[3]. The current study on citrus adds to this body of knowledge by identifying CitWRKY75 as a crucial upstream regulator of anthocyanin accumulation in juvenile tissues. Moreover, the study aligns with findings on the Ruby gene's role in anthocyanin production in various Citrus species[4]. The Ruby gene encodes a MYB transcription factor that controls anthocyanin biosynthesis. Variations in the Ruby gene's activity explain the differences in pigmentation among Citrus species. The identification of CitWRKY75 as an upstream regulator of CitRuby1 further elucidates the complex regulatory network controlling anthocyanin accumulation in citrus. In summary, the study by Huazhong Agricultural University has identified CitWRKY75 as a key transcription factor promoting anthocyanin accumulation in juvenile citrus tissues by regulating the expression of CitRuby1. This discovery enhances our understanding of the genetic mechanisms behind anthocyanin biosynthesis and provides new targets for improving the ornamental and stress-resilience traits of citrus plants.

FruitsGeneticsPlant Science

References

Main Study

1) WRKY75 regulates anthocyanin accumulation in juvenile citrus tissues.

Published 12th August, 2024

https://doi.org/10.1007/s11032-024-01490-9

Related Studies

2) A conserved network of transcriptional activators and repressors regulates anthocyanin pigmentation in eudicots.

https://doi.org/10.1105/tpc.113.122069

3) BBX16, a B-box protein, positively regulates light-induced anthocyanin accumulation by activating MYB10 in red pear.

https://doi.org/10.1111/pbi.13114

4) Changes in Anthocyanin Production during Domestication of Citrus.

https://doi.org/10.1104/pp.16.01701


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