FIN219基因外抑制者SOMBRERO/ANAC033參與遠紅光以及茉莉酸訊息調控下胚軸延長之功能性研究

Abstract

植物演化出各種內在分子機制來適應環境變化。在遠紅光下，光敏素A能被活化，進一步調控植物的生長發育。FIN219/JAR1做為光敏素A的下游，同時參與遠紅光與茉莉酸的訊息傳遞。因此，FIN219/JAR1在兩個訊息傳遞中扮演平衡調節的角色。為了更加了解是否有新的蛋白質調控FIN219/JAR1活性，影響它中介的傳遞路徑，因此，藉由建立fin219-1突變體的基因功能活化突變體種子庫 (activation-tagging mutant pool)，在遠紅光中篩選出編號40-3-1植株抑制fin219-1長下胚軸的外表型。40-3-1植株造成幾個遠紅光與茉莉酸相關基因增加表現，更進一步分析發現T-DNA插在SMB啟動子區域造成其大量表現。由雙突變體smb-3 fin219-2分析，SMB在遠紅光訊息傳遞中扮演正調控者的角色，且與FIN219/JAR1位於同一條訊息傳遞路徑。FIN219/JAR1可以干擾SMB形成二聚體，藉此來降低SMB作為轉錄因子的活性。且發現此機制可能在FIN219/JAR1負回饋調控中相當重要。在調控下胚軸延長方面，SMB也具有劑量效應的現象。總合以上所述，根冠專一性表達的轉錄因子SMB可以藉由參與茉莉酸的訊息傳遞，向上影響下胚軸延長，促進遠紅光的光型態發生。因此，推測在正常植物生長階段，茉莉酸的主要來源可能來自於根部，以此調控地上部的發育型態。

Plants have several strategies to grow under different environmental changes by adjusting their internal mechanisms. Under far-red (FR) light, phyA is activated to regulate plant growth and development. FIN219/JAR1 acts as a phyA-downstream component and a node of crosstalk with jasmonate (JA) signaling. To further understand functions of FIN219/JAR1 in regulation FR light and JA signaling, an activation-tagging pool of fin219-1 was generated. By selection of extragenic suppressors of fin219-1 under FR light, the 40-3-1 mutant line was obtained with a suppression of fin219-1 long-hypocotyl phenotype and the mutation affected the expression of several light- and JA-responsive genes. Further characterization revealed that the 40-3-1 was caused by SMB overexpression. The assay of smb-3 fin219-2 double mutant suggested that SMB acts in the same pathway as FIN219/JAR1 in FR light and JA signaling. FIN219/JAR1 interrupted SMB dimerization and resulted in the repression of SMB activity. Furthermore, SMB regulated FIN219/JAR1 transcription in a negative feedback manner. SMB also showed a dosage effect on the modulation of hypocotyl elongation. Taken together, the root cap-specific transcription factor SMB regulates JA signaling and further affects hypocotyl elongation in FR-mediated photomorphogenesis, which suggests that the main source of JA in normal development of seedlings might be from root to aboveground tissues to regulate several physiological processes.