| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 100 === Plants continuously monitor their surrounding environments and change accordingly their physiological metabolism, growth and development. Different spectrums of light and various hormones are essential to determine the shapes and morphologies of individual plants. During the seedling stage, FAR-RED INSENSITIVE 219 (FIN219) has been shown to participate in phytochrome A and Jasmonate signaling pathways, exerting its functions in photomorphogenesis and JA responses. However, the effects of the posttranslational modifications and related regulatory mechanisms on FIN219 protein levels remain to be elucidated. In silico study shows that FIN219 is predicted to contain casein kinase 2 (CK2) phosphorylation sites, and in vitro kinase assay reveals that FIN219 can be indeed phosphorylated by CK2 on the sites of threonine 55 and threonine 69. Moreover, the unphosphorylated form of FIN219 exhibits lower Kd toward the conjugating process of JA-Isoleucine formation, which means higher affinity to its substrates, and is prone to undergo degradation events. We also observed two FIN219 isoforms in planta whose ratios are modulated by 4,5,6,7-Tetrabromobenzotriazole (TBB), a CK2 inhibitor, and by FR light treatments. Phenotypic examinations show that fin219-2 is less sensitive to TBB inhibition on both hypocotyl and root elongation, and the TBB inhibition of hypocotyl growth are modulated by different intensities of far-red light. Taken together, our study provides the first evidence that CK2-mediated phosphorylation of FIN219 participates in JA signaling during seedling development, and is further involved in the cross talk between JA and FR light signaling pathways.
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