| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 107 === 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.
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