阿拉伯芥RACK1A之延長片段在離層酸反應及葉片發育之功能性研究

Functional study of the extension region of Receptor for Activated C Kinase 1 (RACK1) in abscisic acid response and leaf development in Arabidopsis thaliana

應婉如(Wan-Ru Ying)

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(2018年)

https://doi.org/10.6342/NTU201900304

摘要

Receptor for activated C kinase 1 (RACK1) 是一個普遍存在於真核生物內，且具有高度保留性的基因。在阿拉伯芥中有三個RACK1的基因，包括RACK1A (At1g18080)、RACK1B (At1g48630) 及RACK1C (At3g18130)，其中RACK1A扮演一個顯著表現角色。阿拉伯芥中的RACK1 蛋白質被視為鷹架蛋白，會與其他百種蛋白質交互作用並調節不同生理功能，AtRACK1A曾被報導為離層酸路徑的負向調節者。根據實驗室前人研究，發現雙子葉植物內RACK1蛋白質序列相較於其他物種甚至於單子葉植物多出大約十個胺基酸，然而這十個胺基酸序列對於雙子葉植物RACK1是否具有功能，以及為何不存在於其他物種，皆是尚未清楚。本研究比較RACK1A去除這十個胺基酸序列的大量表現轉殖植物(命名為XRA)、rack1a突變株與AtRACK1A大量表現株，在處理離層酸後觀察離層酸標的基因表現量以及性狀比較，發現離層酸處理後主根長縮短幅度以及氣孔開閉程度，XRA轉殖株皆與rack1a有較相似的性狀，顯示RACK1A特定出現於雙子葉植物的十個胺基酸片段可能參與調節離層酸訊息傳導路徑。另一方面，前人發現阿拉伯芥Translationally Controlled Tumor Protein 1 (AtTCTP1)與RACK1A有交互作用，而TCTP1為Target of Rapamycin (TOR)訊息傳導路徑ㄧ員，協助調節植物生長發育。本研究進一步發現rack1a突變株與XRA以及RACK1A-S286A點突變大量表現株在葉片生長發育相較WT有較小之趨勢，且處理TOR訊息傳導路徑的抑制劑AZD8055，觀察植物根部生長，發現rack1a突變株對於藥劑的
敏感度較低，暗示RACK1A可能參與在TOR路徑。

關鍵字

RACK1 ； 氣孔 ； 離層酸 ； TOR路徑 ； TCTP

並列摘要

Receptor for activated C kinase 1 (RACK1) is a gene that is highly conserved and ubiquitous in eukaryotes. There are three RACK1 genes in Arabidopsis namely, RACK1A (At1g18080), RACK1B (At1g48630) and RACK1C (At3g18130), but AtRACK1A acts as a predominant gene. AtRACK1A is a scaffold protein and interacts with hundreds of proteins to regulate multiple pathways, including abscisic acid (ABA) signaling pathway, plant growth and development. AtRACK1A is known as a negative regulator in ABA signaling pathway. According to a previous study, additional ten amino acids of RACK1 protein were found only in dicots. However, the function of this region is still unknown. RACK1A-XRA overexpression lines (AtRACK1A without these ten amino acids), rack1a mutant line and RACK1A overexpression lines were established to compared their gene expression and phenotype with ABA treatment. The primary root length and stomatal aperture of RACK1A transgenic lines and XRA lines have a phenotype similar to rack1a under ABA treatment. The result indicates that these ten amino acids of RACK1A is related to ABA signaling. On the other hand, Translationally Controlled Tumor Protein 1 (TCTP1) is observed as an interacting protein of RACK1A, and TCTP1 is a regulator of Target of Rapamycin (TOR) pathway and is involved in plant growth. In the present study, leaf size of XRA lines and RACK1A-S286A lines under normal conditions were significantly smaller than WT. With AZD8055 (inhibitor of TOR pathway) treatment, rack1a exhibited hyposensitivity to this reagent in primary root elongation. These suggest that RACK1A may be involved
in TOR pathway, which regulates normal plant growth and development.

並列關鍵字

RACK1 ； stomatal aperture ； abscisic acid ； TOR pathway ； TCTP

參考文獻

Adams, D.R., Ron, D., and Kiely, P.A. (2011). RACK1, a multifaceted scaffolding protein: structure and function. Cell Commun. Signal. 9,22.

Baccelli, I., Lombardi, L., Luti, S., Bernardi, R., Picciarelli, P., Scala, A., and Pazzagli, L. (2014). Cerato-platanin induces resistance in Arabidopsis leaves

through stomatal perception, overexpression of salicylic acid and ethylene signalling genes and camalexin biosynthesis. PloS One 9, e100959.

Benjamin, D., Colombi, M., Moroni, C., and Hall, M.N. (2011). Rapamycin passes the torch: a new generation of mTOR inhibitors. Nat Rev Drug Discov 10, 868-880.

Berkowitz, O., Jost, R., Pollmann, S., and Masle, J. (2008). Characterization of