Studies of Interaction Between FIN219 and Phytochrome A in Arabidopsis
Date Issued
2008
Date
2008
Author(s)
Chiou, Yen-Chang
Abstract
Phytochrome A (phyA) is the photoreceptor of far-red light (FR) (700-750nm) in Arabidopsis. Far-red insensitive 219 (FIN219) has been shown to be a positive signal component in phyA-mediated FR signaling pathway, and fin219 mutant exhibits a long hypocotyl phenotype under FR. How phyA regulates FIN219 remains unknown. Protein gel blot analyses indicated that FIN219 protein was induced once exposure to FR from darkness. Besides, FIN219 was decreased in different phyA alleles, indicating that phyA positively regulates FIN219. Yeast-two-hybrid assays revealed that FIN219 can interact with PHYA, and this interaction was further confirmed by in vitro pull-down assay. Moreover, FIN219 can bind with both Pr and Pfr forms of phyA, but with higher affinity with Pr form. Subcellular localization studies in Arabidopsis protoplasts indicated that FIN219 accumulated in the nuclei, in addition to the cytoplasms. In addition, the hypocotyl length of fin219/phyA double mutant was longer than that of fin219 or phyA single mutant under FR, implying that FIN219 and phyA bind together to regulate hypocotyl elongation in response to FR. Furthermore, RT-PCR assays revealed that some light-regulated genes were differentially affected in fin219/phyA. Transgenic seedlings, FIN219-C274/PHYA-N, harboring the overexpression constructs of the C-terminal 274 amino-acid region of FIN219 and the N-terminal domain of PHYA exhibited a hyposensitive phenotype under FR, suggesting that the interaction between FIN219 and phyA affects FR light signaling. This transgenic line FIN219-C/PHYA-N also revealed a delayed- flowering phenotype under long-day condition. As well, we found that FIN219 may exist as a phosphorylated protein in vivo, and the unphosphorylated form of FIN219 is not stable. Whether FIN219 is a substrate of phyA remains to be elucidated.
Subjects
Arabidopsis
phytochrome A
light signaling transduction
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