| Summary: | 碩士 === 慈濟大學 === 生命科學研究所 === 94 === Arabidopsis gene AtBAG-4 (formally called PB4) is a phyB-interacting component. It was originally isolated from two-hybrid screening with a PHYB bait. BLAST results showed that this protein shares similarity with animal BAG-1 protein. At present, AtBAG-4 is the only BAG domain-containing protein that interacted with phytochrome and may not be existed as a monomer. Results of western blot found that light may induce AtBAG-4 expression and this response was decreased in phyB null mutant. We also examined the phenotypes of Atbag-4 mutant, AtBAG-4 overexpressor, Atbag-4/phyA-211, Atbag-4/phyB-9, Atbag-4/phyA-205 and Atbag-4/phyB-4 double mutant plants to get a better idea what aspect AtBAG-4 affected in phytochrome signaling. From results of phenotypic assay, we found that AtBAG-4 may negatively regulated PhyB-mediated seed germination by modulating PhyB signal. It may slightly affect the flowering time and it is localized in the nucleus. However, AtBAG-4 did not affect the phytochrome- and cryptochrome-mediated inhibition of hypocotyls elongation. Taken together, we
purposed that AtBAG-4 might be a feedback regulator in light induced seed germination pathway. However, this hypothesis needs to be tested. In the future, we will examine the germination phenotype of AtBAG-4OX/phyA-211, AtBAG-4OX/phyB-9, AtBAG-4OX/phyA-205 and AtBAG-4OX/phyB-4 under R or FR light condition and try to understand the relationship between AtBAG-4 expression and seed germination. Although AtBAG-4 seemed to interact with AtCOP1 and AtCHIP weakly, we will look for other components that may be involved in AtBAG-4-mediated seed germination pathway and try to know more about the role of AtBAG-4 in phytochrome signaling.
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