| Summary: | 碩士 === 臺灣大學 === 植物科學研究所 === 98 === For immobile plants, it is important to adjust their development in response to the changes of light environments. Through studying light signaling pathway, we can understand how light affects plant development. Far-red insensitive 219 (FIN219) has been shown to be a positive signal component in phyA-mediated FR signaling pathway, but the molecular mechanisms remain unknown. To further understand the function of FIN219 in light signaling during Arabidopsis development, a yeast two-hybrid approach has been used to isolated FIN219-interacting partners. A gene FIP2 (FIN219-interacting protein 2) encoding a glutamyl- tRNA synthetase (GluRS) was obtained and interacting with the C-terminal domain of FIN219. However, the regulation between FIP2 and FIN219 in light signaling pathway remains to be elucidated.
Furthe confirmation of FIN219 and FIP2 interaction using yeast two-hybrid and bimolecular fluorescence complementation (BiFC) methods indicaded that the N-terminal domain of FIP2 can interact with the C-terminal domain of FIN219. This interaction occurs in the cytoplasm. Furthermore, the fin219 fip2 double mutant exhibited a longer hypocotyl phenotype than its respective parental lines specifically under weak FR light. These data suggest that FIP2 and FIN219 act as a nonallelic noncomplementary genetics relation.
RT-PCR results indicated that the expression levels of light responsive genes such as CHS and RBCS were down-regulated in the fip2 mutant and transgenic seedlings with reduced levels of FIP2 under far-red light, which was consistent with the hyposensitive phenotype of the fip2 mutant as well as the transgenic seedlings with less FIP2 transcript under far-red light. Moreover, transgenic seedlings containing a reduction of FIP2 level resulted in a decrease of anthocyanin accumulation in FR, and led to a defect in the phyA regulated FR blockage of greening and a long hypocotyl phenotype compared to that of wild type under FR.These results implie that FIP2 participates in the control of hypocotyl elongation in FR-mediated light signaling. Besides, the fip2 mutant, fin219fip2 double mutant and transgenic seedlings with reduced FIP2 transcripts were less sensitive to ABA-mediated inhibition of seed germination and root elongation. Taken together, these data indicate that FIP2 may participate in FR-mediated light signaling leading to anthocyanin accumulation and FR-mediated blockage of greening, and ABA-mediated inhibition of seed germination and root elongation.
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