HY5在光與茉莉酸訊息傳遞中的功能性研究

Abstract

光會藉由調控不同的植物荷爾蒙進而影響植物生長發育。LONG HYPOCOTYL5 (HY5)為bZIP 轉錄因子，作用在光訊息傳遞下游並促使光形態發生。近來研究顯示HY5在光訊傳中扮演正向調控者，此外，也參與許多不同荷爾蒙的訊息傳遞中，包含生長激素、吉貝素、乙烯以及離層酸等等；然而，目前仍未有報導指出HY5是否參與在茉莉酸訊息傳遞中。我們先前的證據顯示野生型中的HY5蛋白質含量會受到茉莉酸甲酯(methyl-jasmonate)的誘導並大量累積，然而在fin219-2中，此誘導現象消失。此外，利用yeast two-hybrid發現HY5會與JASMONATE-ZIM-DOMAIN PROTEIN 1(JAZ1)產生交互作用。外表型方面，下胚軸與根長會受到茉莉酸抑制，而花青素則會被誘導累積；我們檢測不同突變株在處理MeJA後的下胚軸與根長的抑制百分比，並且觀察花青素累積情況。結果顯示經MeJA處理後hy5對於下胚軸與根長生長抑制較不敏感，花青素也無法在hy5中被MeJA誘導，推測HY5確實參與在茉莉酸訊息傳遞中，且可能扮演正調控角色。我們的microarray資料分析顯示，比較茉莉酸處理的野生型與hy5突變株發現許多茉莉酸的相關基因表現可能會被正調控或負調控，其中包含JAZs、CHS以及MYBs，後續經由qPCR再次確認。綜合以上所述，我們認為處理MeJA後，HY5受到誘導並大量累積，接著調控許多JA相關基因或是另一類轉錄因子MYBs，進而影響茉莉酸所調控的花青素累積訊息傳遞。

Light crosstalks with different hormones to modulate plant development. LONG HYPOCOTYL5 (HY5), a bZIP transcription factor, acts downstream of light signal transduction and promotes photomorphogenesis in Arabidopsis. Recent studies indicate that HY5 is the integrator of light and multiple hormones such as auxin, gibberellins and abscisic acid. However, there is no evidence showing HY5 involvement in jasmonic acid (JA) signaling. Our previous data showed that HY5 protein level is induced by methyl jasmonate and coronatine that is a phytotoxin and mimics the structure of JA-isoleucine (JA-Ile), an active form of JA. HY5 induction by MeJA substantially reduced in fin219-2.Moreover, our data revealed that HY5 might interact with JAZ proteins in yeast two-hybrid studies. Besides, inhibition of hypocotyl and root elongation, as well as anthocyanin accumulation has been used as indicators of JA-mediated physiological responses. Thus, our data further showed that hy5 mutant lines exhibited insensitive responses to exogenous MeJA treatments. This result implies that HY5 may be a positive regulator in JA signaling pathway. In addition, our microarray data showed that many genes, including JAZ, CHS and MYBs involved in various hormone signaling pathways were up- or down-regulated in hy5 mutant lines with MeJA treatment. Thus, HY5 may participate in JA signaling pathway to regulate JA-mediated anthocyanin accumulation.