ABSTRACT
The deficient mutant for the rice heterotrimeric G protein α subunit gene (RGA1), d1, showed dwarfism and set small seed due to a reduced cell number. Mutants for the rice heterotrimeric G protein ß subunit gene (RGB1) have not been isolated. To determine the functions of RGB1, transgenic rice plants with suppressed expression of RGB1 were studied using the RNAi method. RGB1 knock-down lines showed browning of the lamina joint regions and nodes and reduced fertility, but these abnormality were not observed in d1. Transgenic plants in which the G protein ß subunit was greatly decreased were not obtained, suggesting that the complete suppression of RGB1 mRNA may be lethal. In contrast, the d1 mutants, with complete loss of the G protein α subunit, were fertile and half the size of the WT. These studies suggest that RGB1 has different functions than RGA1.
Subject(s)
GTP-Binding Protein beta Subunits/deficiency , GTP-Binding Protein beta Subunits/genetics , Gene Expression Regulation, Plant , Gene Silencing , Oryza/genetics , Plant Proteins/genetics , GTP-Binding Protein beta Subunits/metabolism , Gene Knockdown Techniques , Mutation/genetics , Oryza/anatomy & histology , Plant Proteins/metabolism , Plants, Genetically Modified , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolismABSTRACT
In the present study, we investigated the function of the heterotrimeric G protein ß-subunit (Gß) gene (RGB1) in rice. RGB1 knock-down lines were generated in the wild type and d1-5, a mutant deficient for the heterotrimeric G protein α-subunit (Gα) gene (RGA1). Both transgenic lines showed browning of the lamina joint regions and nodes that could be attributed to a reduction of RGB1 function, as the abnormality was not observed in d1-5. The RGB1 knock-down lines generated in d1-5 were shorter, suggesting RGB1 to be a positive regulator of cellular proliferation, in addition to RGA1. The number of sterile seeds also increased in both RGB1 knock-down lines. These results suggest that Gßγ and Gα cooperatively function in cellular proliferation and seed fertility. We discuss the potential predominant role of RGB1 in G protein signaling in rice.
