| Summary: | 碩士 === 國立中興大學 === 生物科技學研究所 === 103 === CONSTANS (CO) is a plant-specific transcriptional factor that controls the onset of flowering in response to day-length in photoperiodic pathway. In Arabidopsis CO (AtCO) and 16 CO-like proteins (AtCOLs) contain one or two N-terminal B-box domains involved in protein-protein interaction, and one C-terminal CCT domain for nuclear-localization. Two AtCOLs, AtCOL9/10, functioned as repressors whereas the Oncidium OnCOL9/10 acted as activators to control flowering time and anther dehiscence. In this study, we focused on the functional analysis of two COL homologous genes from Cattleya (CaCOL10) and Phalaenopsis (PaCOL9) orchids. CaCOL10 and PaCOL9 share 76.8% and 77.4% identity of amino acid sequence with that of OnCOL10 and OnCOL9. Thus, CaCOL10 and PaCOL9 could function similarly with OnCOL9/10 in regulating flowering time and anther development. To further characterize the function of CaCOL10 and PaCOL9, we generated three types of Arabidopsis transgenic lines that ectopically express of PaCOL9/CaCOL10 (35S::PaCOL9/35S::CaCOL10), PaCOL9/CaCOL10 fused with a repression domain SRDX (PaCOL9-SRDX/CaCOL10-SRDX), or PaCOL9/CaCOL10 fused with an activation domain VP16 (PaCOL9-VP16/CaCOL10-VP16). 35S::CaCOL10, CaCOL10-VP16, and PaCOL9-VP16 promoted flowering by up-regulating the expression of CO, FT and SOC1. In contrast, CaCOL10-SRDX and 35S::PaCOL9-SRDX delayed flowering in transgenic Arabidopsis. Furthermore, 35S::CaCOL10, CaCOL10-VP16, and PaCOL9-VP16 caused anther indehiscence by down-regulating the expression of NST1, NST2 and Myb85 which are associated with secondary thickening in endothecium. CaCOL10-SRDX and PaCOL9-SRDX didn''t affect the anther dehiscence in transgenic Arabidopsis. These results suggest that CaCOL10 and PaCOL9 may share similar function with OnCOL9/10 in promotion of flower time and inhibition of anther dehiscence, which was opposite to that of AtCOL9/10. Our results provide evidence that COL9/10 genes may behave divergently in monocots orchids and eudicots in regulating flowering time and flower development during evolution.
|
|---|
