阿拉伯芥SOMBRERO/ANAC033與FIN219/JAR1的交互作用參與在遠紅光以及茉莉酸訊息傳遞路徑中之功能性探討

Functional studies of SOMBRERO/ANAC033 and FIN219/JAR1 interaction in the integration of far-red light and jasmonate signaling pathways in Arabidopsis

洪爾慈(Er-Tsi Hung)

指導教授 ： 謝旭亮

國立臺灣大學/生命科學院/植物科學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202224

摘要

阿拉伯芥幼苗在光型態發生的發育階段中，受到光和植物賀爾蒙共同的調控，來更好地適應外界各種環境因子。FAR-RED INSENSITIVE 219 (FIN219/JAR1)可作用在光敏素A (phyA)的下游訊息路徑中，又本身為茉莉酸 (Jasmonate)結合酵素，因此在受光敏素A誘發的遠紅光訊息傳遞路徑，以及茉莉酸訊息傳遞路徑的交互作用當中，扮演平衡調節的重要角色。先前研究中發現了fin219-1的基因外抑制子，是一個專一表達在根冠的轉錄因子SOMBRERO (SMB)。在遠紅光誘導的光型態發生中，位在地下部根冠的SMB和FIN219有物理性交互作用，並且可以透過調控茉莉酸訊息傳遞來進一步影響地上部下胚軸的生長。因此推測有一遠端訊息傳遞參與其中來協調地上部、地下部生長。本研究提出三個假說: (一)SMB透過運送地下部根冠區域的FIN219到地上部；(二)透過運送地下部JA/JA-Ile到地上部；(三)SMB和FIN219一起被運送到地上部。之後在地上部誘發茉莉酸反應，進而來調控受遠紅光誘導的光型態發生的下胚軸延長抑制性。為了驗證假說，建立並檢測了專一表達FIN219在根冠的轉殖株。結果顯示，在強遠紅光下，專一表達在根冠的FIN219可以調控地上部下胚軸延長的抑制性，且此功能依賴正常SMB的存在；該FIN219也可以調控主根生長。此外，根部的FIN219對受遠紅光誘導的下胚軸延長抑制性具有重要性，而對MeJA所誘導的下胚軸生長抑制來說，地上部本身所表達的FIN219反而扮演重要角色。另外，SMB和FIN219對下胚軸的共同調節是需要正常功能的光敏素A存在。地下部FIN219作為可移動的訊號分子，會被運送到地上部，進而調控下胚軸生長。除此之外，遠紅光會促進SMB和FIN219的物理性交互作用，FIN219可能透過抑制SMB的自我活化來降低SMB基因表達。最後，在受遠紅光誘導的光型態發生中，SMB和FIN219蛋白質彼此調控，進而共同調節下胚軸和根部外表型。綜合以上所述，遠紅光可以影響SMB和FIN219的交互作用，並且讓FIN219從根部移動到地上部來誘發JA訊息傳遞，使下胚軸生長受到抑制，促進光型態發生。

關鍵字

遠紅光 ； 光型態發生 ； 遠端訊息傳遞 ； 茉莉酸 ； FIN219/JAR1 ； SMB ； 光敏素A

並列摘要

Arabidopsis thaliana seedlings integrate the external light signal and endogenous phytohormone pathways for better adaptation to different environmental cues when undergo photomorphogenesis. FAR-RED INSENSITIVE 219 (FIN219/JAR1), as a phytochrome A (phyA)-downstream component and a jasmonic acid (JA)-conjugating enzyme, is a key node of the crosstalk between phyA-mediated far-red (FR) light signaling and JA signaling. Previous studies identified a root cap-specific transcription factor SOMBRERO (SMB), which is a suppressor of fin219-1. SMB physically interacted with FIN219. Moreover, root SMB regulated JA signaling and further affected hypocotyl elongation in FR light-mediated photomorphogenesis, which suggested that the long distance signaling may exist to synchronize shoot-root growth. Three hypotheses were then proposed, including: (1) SMB modulates FR light-mediated hypocotyl elongation by the translocation of the root cap-expressed JA signaling component, FIN219, to the aboveground tissues; (2) translocation of the root-derived JA/JA-Ile themselves is proceeded to the aboveground tissues and (3) translocation of FIN219 accompanies with SMB to the aboveground tissues to induce JA response and mediate photomorphogenesis. To further elucidate these speculative hypotheses, the transgenic plants with FIN219 specifically expressed in the root caps were examined to reveal the underlying mechanisms. The results showed that the root cap-specific FIN219 can indeed regulate hypocotyl elongation in SMB-dependent manner under high FR light conditions; it can also regulate the primary root growth. In addition, the root-derived FIN219 was essential for FR-mediated inhibition of hypocotyl elongation, while local expression of FIN219 in the above-ground played vital roles in MeJA-mediated inhibition of hypocotyl elongation. Furthermore, the regulation of hypocotyl elongation by SMB and FIN219 in the root depended on phyA; root FIN219 acted as a mobile signal to translocate from root to aboveground tissues to trigger JA signaling in regulation of the hypocotyl elongation. Besides, FR light enhanced FIN219 and SMB interaction; FIN219 could fine-tune SMB perhaps by repressing SMB self-activation. Finally, SMB and FIN219 mutually regulated each other and worked together to inhibit hypocotyl and root elongation under FR light. Taken together, this study demonstrates that FR light affects the interaction between SMB and FIN219, and induces the migration of FIN219 from root to aboveground tissues to trigger JA signaling in inhibiting hypocotyl elongation, thus promoting photomorphogenesis.

並列關鍵字

far-red light ； photomorphogenesis ； long-distance signaling ； Jasmonates ； FIN219/JAR1 ； SMB ； phyA

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