阿拉伯芥MYB3 及HDA15 在遠紅光下調控花青素生合成之功能性研究

Abstract

植物體內的花青素為一群酚類化合物，除了賦予植物顏色外還具有抗氧化及抗病的功能。花青素的生合成受到光與植物荷爾蒙的調控。MYB3為花青素生合成的負調控者，但目前尚不清楚MYB3如何受到光與植物荷爾蒙的調控。本篇研究發現MYB3與HDA15在遠紅光下具有交互作用，且myb3 hda15 雙突變株在遠紅光及外加茉莉酸處理下相對於野生型及單突變株具有較多的花青素累積。MYB3與HDA15可以共同抑制C4H基因的啟動子活性，因此MYB3與HDA15可能具有協同作用並共同負調控花青素的生合成。MYB3與HDA15也可以共同正調控CHS基因的表現，顯示MYB3與HDA15能夠同時正調控與負調控花青素合成相關基因的表達。myb3 及 hda15 單突變株在遠紅光及藍光環境下比野生型具有較長的下胚軸，但myb3 hda15 雙突變株卻有較單突變株及野生型較短的下胚軸，顯示MYB3與HDA15在調控幼苗光型態發生及下胚軸生長時可能具有相互拮抗的現象。HY5 是光型態發生及花青素生合成的正調控者，其生理功能需要依賴HDA15。總而言之，我們發現MYB3會與HY5競爭與HDA15結合，MYB3 與HDA15兩者具有協同性並能共同調控遠紅光及茉莉酸處理下花青素的生合成，因此MYB3會介導光與茉莉酸訊息傳遞路徑間的互動。

Anthocyanins in plants are phenolic compounds with various colors and function as antioxidants and antimicrobials. The biosynthesis of anthocyanin is regulated by light and various plant hormones. MYB3 functions as a negative regulator in the control of anthocyanin levels. However, how light and plant hormones regulate MYB3 functions remains largely unknown. We found that MYB3 interacted with HDA15 under far-red (FR) light. The double mutant myb3 hda15 showed higher levels of anthocyanin accumulation than wild type and single mutants under FR light and methyl-jasmonate (MeJA) treatment. MYB3 and HDA15 could work together to repress the C4H promoter activity, which suggests that MYB3 and HDA15 worked synergistically as negative regulators of anthocyanin content under FR light and MeJA treatment. MYB3 and HDA15 could work together to promote the CHS gene expression, which suggests that MYB3 and HDA15 act as positive and negative regulators in regulating anthocyanin biosynthesis-related gene expression under FR and JA treatment. In addition, myb3 and hda15 single mutants had a long hypocotyl phenotype under FR and blue light, but the myb3 hda15 double mutant had a shorter hypocotyl than single mutants and wild type, which implies that MYB3 and HDA15 mutually antagonized each other to modulate photomorphogenesis and hypocotyl elongation. Besides, HY5 is a positive regulator of photomorphogenesis and anthocyanin biosynthesis. It interacts with HDA15, and its function depends on HDA15. Further evidence revealed that MYB3 competed with HY5 for binding with HDA15 in negatively and synergistically regulating anthocyanin biosynthesis in Arabidopsis under FR light and MeJA treatment, which suggests the crosstalk between light and jasmonate signaling.