阿拉伯芥FIN219、光敏素A與AtGSTU17在遠紅光與荷爾蒙間相互作用之功能性研究

Abstract

PART I 植物生長發育受到光和植物荷爾蒙的調節。 FAR-RED INSISSITIVE 219（FIN219）/ JASMONATE RESISTANT 1（JAR1）參與光敏素A參與的遠紅光訊息傳遞，並且能合成茉莉酸-異亮胺酸。先前證據指出 遠紅光和茉莉酸的訊息傳遞是整合的。然而，其相互作用的分子機制尚未明瞭．我們發現 phyA 突變體具有茉莉酸敏感的外表型。此外，雙突變株 fin219-2phyA-211 對遠紅光下的幼苗發育具有協同作用。FIN219 和 phyA 調節了光和茉莉酸相關基因的表達，彼此為相互作用的必要條件。茉莉酸相反地調控 phyA 和 FIN219 在植物體內的含量，並且在遠紅光和黑暗條件下，FIN219 與 phyA 彼此拮抗。此外，FIN219 在延長照射遠紅光下與 phyA 相互作用，MeJA 可增強兩者在黑暗和遠紅光下的交互作用並與 COP1 結合。FIN219 和 phyA 的交互作用主要發生在細胞質，它們調節了遠紅光下彼此在細胞內的位置。此外，分子證據顯示，FIN219 和 phyA 以交互作用的方式相互拮抗，以調節下胚軸延長和相關基因表現。這些結果證明在遠紅光下 FIN219-phyA-COP1 結合的重要機制，及 MeJA 可能幫助光活化態的 phyA 引發阿拉伯芥幼苗的光形態發生。 PART II 穀胱甘肽 S-轉移酶(GST)已被充分證明參與在生物和非生物逆境的多方面，特別是解毒過程。它們是否調節植物發育仍不清楚。我們通過逆轉錄聚合酶鏈反應來分離阿拉伯芥的植物 GST，AtGSTU17 被證明其表達在所有光照條件下，由多種光接受體調節，特別是光敏素A。進一步的生理研究顯示，AtGSTU17 參與了幼苗發育的多方面，包括下胚軸延長，花青素積累，以及遠紅光參與的綠化抑制。 AtGSTU17 的突變體導致在生長素存在下幼苗重量和側根數減少，以及與不同的 phyA 突變體相似對離層酸抑制根長不敏感。此外，atgstu17 的根部性狀與通過添加生長素或離層酸的 AtGSTU17 啟動子活性 GUS 染色結果可相互對照。用遠紅光照射或離層酸處理的野生型和 atgstu17 幼苗的微陣列分析顯示，AtGSTU17 可能通過正向調節一些光訊息分子並負調控一群生長素相關基因來調節下胚軸延長，在離層酸的存在下控制生長素傳輸蛋白來負調控根部發育。因此，我們的結果顯示，AtGSTU17 參與光訊號傳導，並可能通過與 phyA 和植物荷爾蒙的協調，及影響穀胱甘肽恆定來調節阿拉伯芥的生長發育。

PART I Plant development is often regulated by the integration of light and phytohormones. FAR-RED INSENSITIVE 219 (FIN219)/JASMONATE RESISTANT 1 (JAR1) participates in phytochrome A (phyA)-mediated far-red (FR) signaling and is a jasmonate (JA)-conjugating enzyme for the formation of an active JA-isoleucine. Accumulating evidence indicates that FR and JA signaling is integrated. However, the molecular mechanisms underlying their interaction remain largely unknown. Here, we found that the phyA mutant has a JA-hypersensitive phenotype. Moreover, the double mutant fin219-2phyA-211 showed a synergistic effect on seedling development under FR light. FIN219 and phyA regulated the expression of light- and JA-responsive genes with a mutually functional requirement of each other. JA regulated phyA and FIN219 levels oppositely, and both antagonized each other under FR light and dark conditions. Furthermore, FIN219 interacted with phyA under prolonged FR light, and MeJA could enhance their interaction along with CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a repressor of photomorphogenesis, in the dark and FR light. The FIN219 and phyA interaction occurred mainly in the cytoplasm, and they regulated their mutual subcellular localization under FR light. Furthermore, molecular evidence revealed that FIN219 and phyA antagonized each other in a mutually functional manner to modulate hypocotyl elongation and gene expression. Overall, these data identified a vital mechanism of the FIN219–phyA–COP1 association in response to FR light, and MeJA may allow the photoactivated phyA to trigger photomorphogenic development of Arabidopsis seedlings. PART II Glutathione S-transferases (GSTs) have been well documented to be involved in diverse aspects of biotic and abiotic stresses, especially detoxification processes. Whether they regulate plant development remains unclear. Here, we report on our isolation by reverse transcription-polymerase chain reaction of a plant GST, AtGSTU17, from Arabidopsis (Arabidopsis thaliana) and demonstrate that its expression is regulated by multiple photoreceptors, especially phytochrome A (phyA) under all light conditions. Further physiological studies indicated that AtGSTU17 participates in various aspects of seedling development, including hypocotyl elongation, anthocyanin accumulation, and far-red light-mediated inhibition of greening with a requirement of functional phyA. The loss-of-function mutant of AtGSTU17 (atgstu17) resulted in reduced biomass of seedlings and number of lateral roots in the presence of auxin, as well as insensitivity to abscisic acid (ABA)-mediated inhibition of root elongation, with similarity to different phyA mutant alleles. Moreover, the root phenotype conferred by atgstu17 was reflected by histochemical b-glucuronidase staining of AtGSTU17 promoter activity with the addition of auxin or ABA. Further microarray analysis of wild-type Columbia and atgstu17 seedlings treated with far-red irradiation or ABA revealed that AtGSTU17 might modulate hypocotyl elongation by positively regulating some light-signaling components and negatively regulating a group of auxin-responsive genes and modulate root development by negatively controlling an auxin transport protein in the presence of ABA. Therefore, our data reveal that AtGSTU17 participates in light signaling and might modulate various aspects of Arabidopsis development by affecting glutathione pools via a coordinated regulation with phyA and phytohormones.