阿拉伯芥RACK1A參與調控離層酸反應之分子機制

Molecular mechanism of Receptor for Activated C Kinase 1 A (RACK1A) in ABA responses in Arabidopsis thaliana

翁嘉祺(Chia-Chi Weng)

指導教授 ： 張英峯

國立臺灣大學/生命科學院/植物科學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202101618

摘要

已知在哺乳動物中，活化態蛋白質激酶C受體RACK1具備「鷹架」（scaffold）的功能，會與多種蛋白質發生交互作用。在真核生物中，RACK1蛋白質序列在真核生物間具有高度保守性。在植物中，許多蛋白質作為RACK1的配體(ligand)，參與各種訊號傳遞路徑和細胞生理生化作用，其中轉譯調控腫瘤蛋白質TCTP1被報導參與生長調節、植物激素訊號途徑、以及逆境反應。此外，阿拉伯芥RACK1A被報導為離層酸訊號的負向調控者，且AtRACK1A基因表現量下降的突變株呈現抗旱的表現型。然而，RACK1A與TCTP1如何共同參與離層酸訊號途徑，進而引發植物抗逆境反應，其功能與作用機制仍未知。本研究中欲探討阿拉伯芥RACK1A與TCTP1間的交互作用是否共同參與調控離層酸訊號途徑，首先以雙分子螢光互補驗證RACK1A和TCTP1間的交互作用，並進一步嘗試利用阿拉伯芥突變株和轉殖株對RACK1A及TCTP1進行功能性和離層酸反應機制的探討。透過葉部表現型的觀察可知，與Col-0植株相比，突變株rack1a以及tctp1 rack1a雙基因突變株呈現較遲緩的營養生長速率。種子萌發及子葉綠化試驗結果顯示，於幼苗營養生長前期，突變株rack1a以及tctp1 rack1a雙基因突變株對於離層酸處理皆表現較高的敏感度。離層酸所誘導的氣孔關閉試驗結果亦顯示，突變株rack1a以及tctp1 rack1a雙基因突變株的氣孔關閉反應，對於離層酸處理的敏感度皆較高。此外， 過表現TCTP1的轉殖株經離層酸處理後，其RACK1A蛋白質累積量有減少的趨勢。對於RACK1在離層酸反應中擔任負向調控者的觀點，本篇研究為其提供了更多支持的證據，且以上試驗結果亦顯示TCTP1可能負向調控RACK1A並與之共同參與調控離層酸訊號途徑。

關鍵字

活化態蛋白質激酶C受體 ； 離層酸 ； 轉譯調控腫瘤蛋白質 ； 乾旱 ； 發育缺陷 ； 氣孔關閉

並列摘要

In mammals, receptor for activated C kinase 1 (RACK1) is known for providing a scaffold for interaction with various ligands. The protein sequence of RACK1 is highly conserved in eukaryotes. The interacting partners of plant RACK1 participate in numerous signaling pathways and cellular processes, for instance, translationally controlled tumor protein (TCTP) is associated with growth regulation, hormone signaling, and stress responses. RACK1 was reported to negatively regulate abscisic acid (ABA) responses in Arabidopsis. In addition, previous studies indicate that loss-of-function mutation in AtRACK1A exhibited drought tolerant phenotype. However, how RACK1 and TCTP are involved in ABA and environmental stress responses in plants remains elusive. The interaction of AtRACK1A and AtTCTP1 was hypothesized to mediate ABA responses in this study. To gain more evidences to support this hypothesis, the genetic and molecular characterization of RACK1A and TCTP1 was carried out. The bimolecular fluorescence complementation (BiFC) assays indicated that RACK1A physically interacted with TCTP1. According to the examination of the rate of leaf production, retardant vegetative growth could be detected in rack1a mutant, as well as double mutant tctp1 rack1a. Multiple assays upon ABA treatment were subsequently performed. Exhibition of the ABA hypersensitivity revealed in single mutant rack1a and double mutant tctp1 rack1a upon ABA exposure during early seedling development and stomatal closure. Furthermore, the inhibition of RACK1A protein accumulation under ABA treatment in TCTP1 overexpression line seemed to be aggravated, while that in tctp1 mutant was relatively mild. Taken together, TCTP1 is suggested to negatively regulate RACK1A in ABA responses.

並列關鍵字

RACK1A ； ABA ； TCTP1 ； drought ； developmental defects ； stomatal closure

參考文獻

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