FIN219和SPA1在遠紅光及茉莉酸訊息傳遞中的功能性研究

Abstract

在模式植物阿拉伯芥的研究中，已知光敏素A (phytochrome A) 是負責接收遠紅光的光接受體，並且藉由一系列的分子將遠紅光的訊息傳遞到細胞內。FAR-RED INSENSITIVE 219 (FIN219)/JAR1 是作用在光敏素A訊息下游的一正向因子，並且其經由轉錄、轉譯後產生的蛋白質為一酵素，可以催化茉莉酸 (Jasmonic acid) 接上異亮氨酸 (Isoleucine)。而本篇研究發現在fin219-2突變株中，光敏素A訊息中的負向調控因子SUPPRESSOR OF PHYA-105 1 (SPA1) 的轉錄表現量大量上升；為了瞭解FIN219和SPA1之間的基因調控關係，我們從雙突變株miSPA1/fin219-2，以及SPA1大量表現在fin219-2突變株(SPA1ox/fin219-2) 和FIN219大量表現在spa1突變株 (FIN219ox/spa1)的阿拉伯芥轉殖株的性狀觀察得知在遠紅光訊息中，SPA1是位在FIN219的下游。藉由分析spa1突變株的性狀，顯示下胚軸對於茉莉酸的反應需要SPA1，此外從基因表現檢測的結果發現茉莉酸所誘導表現的基因VSP1和MYC2都受到SPA1的正向調控，兩者顯示SPA1確實正向參與在茉莉酸的訊息傳遞之中。因此在遠紅光下，FIN219對於SPA1的抑制作用提供茉莉酸訊息傳遞中一個負回饋機制，來減緩植物對於茉莉酸的反應強度；此外分析轉殖株對於茉莉酸的反應，發現跟SPA1相比，FIN219在茉莉酸訊息中為主要的調控者。綜合研究的結果，顯示FIN219和SPA1之間的調控關係，反應出遠紅光訊息以及茉莉酸訊息之間的交互作用，以及對於彼此訊息傳遞的影響。

In Arabidopsis, phytochrome A is one of the photoreceptors and responsible for far-red light signal transduction. FAR-RED INSENSITIVE 219 (FIN219)/JAR1 is a positive component in the downstream of phytochrome A signaling and encodes a jasmonic acid (JA)-amido synthatase, catalyzing the synthesis of JA-isoleucine (JA-Ile). In this study, it is found that the transcript of SUPPRESSOR OF PHYA-105 1 (SPA1), a repressor of phytochrome A-mediated responses, is greatly enhanced in the fin219-2 mutant under continuous far-red light (FRc). To determine functional regulation between FIN219 and SPA1, we generated the mimic double mutant (miSPA1/fin219-2), SPA1 overexpression in fin219-2 (SPA1ox/fin219-2), and FIN219 overexpression in spa1 (FIN219ox/spa1) transgenic plants, and the results showed that SPA1 acts downstream of FIN219 in FRc. Phenotypic analysis of the spa1 mutant suggests that SPA1 is required for hypocotyl response to MeJA; besides, Real-time PCR results indicated that the induction of two JA-responsive genes, VSP1 and MYC2, is reduced in spa1 mutant. These data indicate that SPA1 is a positive regulator in JA signaling under FRc condition. Thus, FIN219 may serve as a negative feedback through inhibiting SPA1 to control the magnitude and duration of JA responses in far-red light. By examining JA responses of these transgenic plants, the results reveal that FIN219 plays a major role in JA signaling compared with SPA1. Taken together, these data indicate that FIN219 and SPA1 show genetic interactions and regulatory relation to provide a critical mechanism in the integration of far-red light and JA signaling.