阿拉伯芥Receptor for Activated C-Kinase 1在乾旱逆境下之功能性研究

Receptor for Activated C-Kinase 1 (RACK1)是一個分子量為36-kDa左右的鷹架蛋白質，普遍存在於動物和植物中。在阿拉伯芥中，有三個基因可以轉譯出RACK1蛋白質，分別命名為RACK1A (At1g18080)、RACK1B (At1g48630) 和RACK1C (At3g18130)。阿拉伯芥中的RACK1蛋白質會參與在賀爾蒙反應和植物生長發育的過程中，且會與40S核醣體發生交互作用。目前，RACK1被視為一個多功能性的鷹架蛋白質，在不同的訊息傳遞途徑中扮演重要的角色。除此之外，RACK1在離層酸反應中扮演一個負向調控的角色。然而，RACK1A的生理功能及究竟是與哪些蛋白質發生交互作用，共同參與或調控這些訊息傳遞的過程，都是尚未清楚的部分。本研究利用酵母菌雙雜合篩選的方式，找到了許多有可能與AtRACK1A產生交互作用的蛋白質，其中包括Translationally Controlled Tumor Protein (TCTP)，同時進一步以酵母菌雙雜合系統及雙分子螢光互補實驗證實AtTCTP與AtRACK1A是有直接交互作用。藉由分析RACK1A的蛋白質序列，我們也發現到有一段含有10個胺基酸的序列只會存在於雙子葉植物的RACK1中。之後建立AtRACK1A大量表現株及篩選rack1突變株，發現AtRACK1A會參與在根與葉的生長發育中。在模擬乾旱逆境下， AtRACK1A基因表現下降。在rack1a突變株中，被離層酸所調控的乾旱標的基因表現上升。更進一步， rack1a突變株的水分散失性較野生型稍低，經由離層酸處理後，其氣孔關閉程度較高，再者處理乾旱逆境後，其存活率亦比野生型高許多，這些結果皆暗示著AtRACK1A除了正向調節生長發育外，亦可能負向參與調控阿拉伯芥對乾旱逆境的耐受性。

關鍵字

RACK1 ；鷹架蛋白；氣孔；離層酸； TCTP ；乾旱

並列摘要

Receptor for Activated C-Kinase 1 (RACK1) is a 36-kDa protein, which is highly conserved in both animals and plants. There are three RACK1 genes in Arabidopsis thaliana, namely RACK1A (At1g18080), RACK1B (At1g48630) and RACK1C (At3g18130). AtRACK1 is involved in multiple hormone responses, developmental processes, and associated with 40S ribosomes in Arabidopsis. Notably, RACK1 is regarded as a versatile scaffold protein which serves as a nexus for multiple signal transduction pathways. Moreover, AtRACK1 plays a negative regulator role under abscisic acid (ABA) responses. However, the specific interactions between AtRACK1 and its binding partners are still unclear. Some proteins and transcription factors that can interact with AtRACK1A were identified by yeast two-hybrid screen, including Translationally Controlled Tumor Protein (TCTP). Furthermore, yeast two-hybrid and bimolecular fluorescence complementation were used to study the interactions between TCTP and RACK1A, and results confirmed that RACK1A interacts with TCTP directly. Protein sequence analysis revealed that a short sequence containing 10 amino acids only exists in dicots. After generating the AtRACK1A overexpression line and isolating the rack1 mutant line, we found AtACK1A participates in roots and rosette leaves development based on phenotype. On the other hand, AtRACK1A expression was down regulated by 20% mannitol treatment. Furthermore, some drought response marker genes that are regulated by ABA are highly expressed in rack1a. After ABA treatment, rack1a showed greater ABA-mediated stomatal closure. We also found that the rack1a showed greatly enhanced tolerance to drought. In summary, these results showed that AtRACK1A not only positively can regulate plant development but also imply that AtRACK1A may negatively participate in the drought stress tolerance.

並列關鍵字

RACK1 ； scaffold protein ； stomata ； ABA ； TCTP ； drought

參考文獻

林靖凰，2011。阿拉伯芥RACK1A是否會與14-3-3蛋白有分子上的交互作用？國立台灣大學植物科學研究所。

魯建宇，2011。暖溫層積處理過程中山櫻花休眠種子的基因調控。國立台灣大學植物科學研究所。

Bommer, U.A., and Thiele, B.J. (2004). The translationally controlled tumour protein (TCTP). Int. J. Biochem. Cell Biol. 36, 379-385.

Boex-Fontvieille, E., Daventure, M., Jossier, M., Zivy, M., Hodges, M., and Tcherkez, G. (2013). Photosynthetic control of Arabidopsis leaf cytoplasmic translation initiation by protein phosphorylation. PloS One 8, e70692.

Chang, I.F., Szick-Miranda, K., Pan, S., and Bailey-Serres, J. (2005). Proteomic characterization of evolutionarily conserved and variable proteins of Arabidopsis cytosolic ribosomes. Plant Physiol. 137, 848-862.

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阿拉伯芥Receptor for Activated C-Kinase 1在乾旱逆境下之功能性研究

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