Investigation of functional relationship between FIN219 and photomorphogenic mutants in Arabidopsis

• Main Authors: Chiung-Huei Huang, 黃瓊慧
• Other Authors: 謝旭亮
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/31018062621168969125

碩士 === 國立臺灣大學 === 植物科學研究所 === 93 === phyA is the photoreceptor of far-red light perception in Arabidopsis and mediates the inhibition of the hypocotyl elongation under FR light. phyA has two domains : the N-terminal photosensory domain with a chromophore-binding site and the C-terminal domain which contains signaling motifs such as a kinase domain. FIN219 (far-red insensitive 219) is involved in phytochrome A-mediated inhibition of hypocotyl elongation in FR signaling. Two coiled-coil domains, believed to be involved in protein-protein interactions, are found in FIN219 with one in the N-terminus and the other in the C-terminus. The N-terminal region of FIN219 has 43% similarity at amino acid levels to the GAF domain of PHYA. GH3-10 is a member of the GH3-like gene family in Arabidopsis. Sequence comparison between FIN219 and GH3-10 indicates that there is 47% identity at amino acid level. Hence, we try to understand the functional relationship among FIN219, GH3-10 and phyA to reveal the physiological significance of the similarity. Yeast 2-hybrid interaction studies have revealed that FIN219 can interact with the full length of GH3-10 and the C-terminus of PHYA. Epistatic analysis reveals that FIN219 functions in downstream of the photoreceptor phyA, and its expression is much reduced in the phyA mutant only under FR condition, which suggests that FIN219 function is dependent on the presence of phyA. In addition, the transgenic plants overexpressing the full-length, N- or -C terminal regions of PHYA in wild type background display shorter hypocotyl phenotype as compared to wild type under FR. Other phenotypes such as anthocyanin accumulation, chlorophyll contents, CHS gene expression and flowering time mediated by phyA are consistently enhanced or the same as wild type when N- or -C terminal regions of PHYA are overexpressed in wild type rather than in phyA mutant, which implies that both the N-terminal and the C-terminal domains are functional and able to trigger signal transductions only in the presence of phyA.