阿拉伯芥中光敏素A對於FIN219/JAR1蛋白質 磷酸化修飾在遠紅光與茉莉酸訊息傳遞的功能性研究

Abstract

植物是屬於光合自營生物，能夠藉由感知光源來調控植物的發育與生理反應。在植物中，具有許多不同種類的光受體來共同調控植物幼苗發育。其中，光敏素A能專一地感知遠紅光，並且藉由與COP1蛋白質的交互作用，來調控植物幼苗的光型態發生。FAR-RED INSENSITIVE 219 (FIN219)/JAR1除了作為催化茉莉酸(JA)與胺基酸Isoleucine(Ile)結合成JA-Ile的合成酵素外，同時也扮演調節遠紅光與茉莉酸訊息傳遞的重要角色。在先前研究中，已知phyA具有磷酸激酶(kinase)的活性，並已確認參與反應的受質。在過去的研究成果中，phyA被認為可能會參與調控FIN219的磷酸化，並發現FIN219磷酸化與否會影響其自身酵素活性。然而，FIN219的磷酸化參與在遠紅光與茉莉酸訊息傳遞的調控機制尚未明瞭。為了更加了解FIN219受phyA磷酸化的調控機制，本研究進行試管外的磷酸化實驗。結果顯示FIN219的N端區域可能受到phyA的磷酸化。進一步藉由建立磷酸化位點改變的轉殖株，來了解磷酸化與否對於植物體的影響；結果發現，僅有去磷酸化FIN219的轉殖株才能互補fin219-2的外表型，而磷酸化FIN219的轉殖株則否。另外，去磷酸化FIN219轉殖株也會造成遠紅光與茉莉酸訊息傳遞相關基因增加表現，而磷酸化FIN219轉殖株則無法。綜合上述，去磷酸化FIN219可以增強茉莉酸與遠紅光訊息傳遞，而磷酸化FIN219則不具有此功能。因此，推測FIN219磷酸化可作為一個調控遠紅光和茉莉酸訊息傳遞的開關。

As photoautotrophs, plants have the capability to perceive light, and regulates internal developmental and physiological responses. Several photoreceptors co-regulate seedling growth and development. Among them, phyA perceives FR light specifically and regulates FR light signaling by interacting with various regulators, including CONSTITUTIVE PHOTOMOPHOGENIC1 (COP1) to promote photomorphogenic development of seedlings. As a JA-conjugating enzyme, FIN219/JAR1 is a key component to crosslink JA and FR light signaling. Previously, it has been reported that phyA has kinase activities and its substrates were identified. According to our previous results, phyA is potentially involved in the phosphorylation of FIN219 and the phosphorylation of FIN219 would alter its activity. However, the regulatory mechanism of FIN219 phosphorylation under FR light and JA signaling is still unknown. To further identify the phosphorylation of FIN219 by phyA under FR, an in vitro kinase assay was performed. The results showed that the N-terminal region of FIN219 would be phosphorylated by phyA. Furthermore, the transgenic lines with mutations in phosphorylation sites were generated. Among them, only the dephosphorylated FIN219 transgenic lines, 35S:FIN219-S100A/fin219-2, showed a rescue of rescued fin219-2 mutant phenotype, but the phosphorylated FIN219 transgenic lines, 35S:FIN219-S100D/fin219-2, did not. Furthermore, the JA and FR light responsive genes were upregulated in 35S:FIN219-S100A/fin219-2, but not in 35S:FIN219-S100D/fin219-2. In summary, dephosphorylated FIN219 could enhance the JA and FR light responses, while phosphorylated FIN219 could not. Collectively, these results suggest that phyA-mediated phosphorylation of FIN219 could serve as a switch to regulate FR light and jasmonate signaling.