探討遮蔭光下阿拉伯芥中受光與茉莉酸調控的FIN219/JAR1與組蛋白去乙醯酶HDA15的調控關係

Abstract

植物演化出許多分子機制適應環境中光條件的變化。在阿拉伯芥中遮蔭迴避效應即是個經典的例子。FIN219/JAR1已知會催化茉莉酸(jasmonate)結合異白胺酸(isoleucine, Ile)形成有活性JA-Ile，來參與茉莉酸訊息傳遞，並且也會參與阿拉伯芥的遮蔭迴避效應。其生理功能似乎透過調節COP1在細胞中的位置或轉錄因子ATHB2和PIF5等基因表現來負調控遮蔭迴避效應。因此FIN219/JAR1不僅參與光訊號路徑也參與賀爾蒙訊息傳遞。目前已有文獻顯示轉錄因子HY5可藉由與組蛋白去乙醯酶15(HDA15)交互作用來共同調節植物的光型態發生；且之前也已發現FIN219/JAR1在光訊息與茉莉酸訊息傳遞中會正調控HY5的蛋白含量。更進一步的文獻證實HY5也會負調控遮蔭迴避效應。但HDA15是否會參與遮蔭迴避效應到目前仍然不清楚。本研究發現HDA15會負調控阿拉伯芥的遮蔭迴避效應，進一步也發現在遮蔭環境下HDA15與HY5仍會有交互作用，因此推測HDA15與HY5藉由交互作用來共同調節遮蔭迴避效應的反應。另外透過對fin219-2 hy5-ks50以及pGR219 hy5-ks50雙突變株在遮蔭環境下的外表型分析，顯示FIN219/JAR1和HY5很可能位於同一條訊號路徑上，且在遮蔭環境底下FIN219/JAR1也會促進HY5蛋白質的穩定性。綜合上述，推測在遮蔭環境底下FIN219/JAR1可藉由調節HY5蛋白質的穩定性，進而影響HY5和HDA15的交互作用來共同調節阿拉伯芥遮蔭迴避效應。

Plants have evolved many molecular mechanisms to adapt to changes in light conditions. In Arabidopsis, the shade avoidance response is a typical example. Our laboratory found that FIN219/JAR1, an enzyme known to catalyze the formation of JA-isoleucine (JA-Ile), participates in JA signaling and is also involved in the shade avoidance response in Arabidopsis. Its physiological function appears to negatively regulate the shade avoidance by regulating the subcellular localization of COP1 and the expression of ATHB2 and PIF5. Therefore, FIN219/JAR1 is involved not only in light signaling but also in hormonal signaling pathways. It has been shown that transcription factor HY5 can co-regulate the photomorphogenesis of plants by interacting with HDA15. Previous studies also found that FIN219/JAR1 greatly affected HY5 protein levels under far-red light and JA treatment conditions. Other studies also showed that HY5 negatively regulated shade avoidance responses. However, whether HDA15 is involved in the shade avoidance responses remains unclear. This study reported that HDA15 negatively regulated the shade avoidance response, and HDA15 and HY5 also could interact with each other under shading conditions, suggesting that their interaction might regulate shade avoidance responses. In addition, the phenotypic analyses by using fin219-2 hy5-ks50 and pGR219 hy5-ks50 double mutants showed that FIN219/JAR1 and HY5 are likely to be on the same signaling pathway to modulate hypocotyl elongation under shading condition. Moreover, FIN219/ JAR1 may promote the stability of HY5 protein. In summary, FIN219/JAR1 regulates shade avoidance responses by regulating the stability of HY5 protein, leading to the effects on HY5 and HDA15 interaction under shade conditions.