New Discovery Reveals How Kale Gets Its Color

Jim Crocker
13th June, 2024

New Discovery Reveals How Kale Gets Its Color

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Shenyang Agricultural University discovered a key gene, BoDFR1, that controls anthocyanin production in kale
  • A variation in the BoDFR1 promoter affects its activity, leading to different levels of pink coloration in kale
  • The study identified BoMYB4b as a repressor that reduces BoDFR1 expression, and BoMIEL1 as a protein that degrades BoMYB4b, promoting anthocyanin accumulation
Anthocyanin, a pigment responsible for the vivid coloration in plants and beneficial to human health, has been a focal point of plant biology research. Kale (Brassica oleracea var. acephala), known for its anthocyanin-rich leaves, serves as an excellent model to study the biosynthesis and regulation mechanisms of this pigment. Despite its importance, the molecular mechanisms underlying anthocyanin accumulation in kale have remained largely unexplored. A recent study conducted by researchers at Shenyang Agricultural University[1] sheds light on this intricate process, revealing a novel regulatory module that governs anthocyanin accumulation in kale. The study identified BoDFR1 as a key gene controlling anthocyanin biosynthesis in kale. The researchers discovered a 369-bp insertion/deletion (InDel) variation in the BoDFR1 promoter between two kale inbred lines with different pink coloration. This variation resulted in reduced transcriptional activity of the BoDFR1 gene in the light-pink line. The 369-bp insertion was used as a bait in yeast one-hybrid screening, leading to the identification of an R2R3-MYB repressor, BoMYB4b. Knockdown of BoMYB4b resulted in increased BoDFR1 expression and anthocyanin accumulation, highlighting its role as a negative regulator. The study further identified an E3 ubiquitin ligase, BoMIEL1, which mediates the degradation of BoMYB4b, thereby promoting anthocyanin biosynthesis. This finding aligns with previous research showing that ubiquitin ligases can negatively regulate anthocyanin biosynthesis by targeting key regulatory proteins for degradation. For instance, MdMIEL1 in apple was found to ubiquitinate and degrade MdMYB1, a crucial regulator of anthocyanin accumulation[2]. The new study extends this understanding to kale, demonstrating that BoMIEL1 facilitates anthocyanin accumulation by degrading the repressor BoMYB4b. Interestingly, the expression level of BoMYB4b was found to be significantly reduced by light signals. This reduction was attributed to the direct repression of BoMYB4b promoter by the light-signaling factor BoMYB1R1. This finding is particularly noteworthy as it integrates environmental signals, such as light, into the regulation of anthocyanin biosynthesis. Previous studies have shown that environmental factors can influence anthocyanin accumulation. For example, PHR1 in apple interacts with MdWRKY75 to enhance anthocyanin biosynthesis in response to phosphate starvation[3]. The current study adds another layer to this understanding by showing how light signals can modulate the expression of key regulatory genes in kale. The study's findings reveal a novel regulatory module comprising BoMYB1R1, BoMIEL1, BoMYB4b, and BoDFR1 that finely regulates anthocyanin accumulation in kale. This regulatory network is reminiscent of the MYB-bHLH-WD repeat (MBW) complexes that have been shown to regulate anthocyanin biosynthesis in other plant species, such as petunia and Arabidopsis[4]. In these systems, MYB repressors and activators, along with other regulatory proteins, form complex feedback loops to ensure appropriate levels of anthocyanin pigmentation in response to developmental and environmental cues. In summary, the study conducted by Shenyang Agricultural University provides significant insights into the molecular mechanisms regulating anthocyanin accumulation in kale. By identifying key regulatory genes and their interactions, the research establishes a scientific foundation for the genetic improvement of leaf color traits in kale. Moreover, it offers a valuable reference for future studies on plant coloration, potentially leading to broader applications in agriculture and horticulture.

GeneticsBiochemPlant Science

References

Main Study

1) A novel three-layer module BoMYB1R1-BoMYB4b/BoMIEL1-BoDFR1 regulates anthocyanin accumulation in kale.

Published 12th June, 2024

https://doi.org/10.1111/tpj.16881

Related Studies

2) Apple RING E3 ligase MdMIEL1 inhibits anthocyanin accumulation by ubiquitinating and degrading MdMYB1 protein.

https://doi.org/10.1093/pcp/pcx129

3) The E3 ubiquitin ligase SINA1 and the protein kinase BIN2 cooperatively regulate PHR1 in apple anthocyanin biosynthesis.

https://doi.org/10.1111/jipb.13538

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

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


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