Function and expression pattern of the α subunit of the heterotrimeric g protein in rice

Abstract

The d1 mutant, which is deficient for the heterotrimeric G-protein α subunit (Gα) gene of rice, shows dwarfism and sets small round seeds. To determine whether dwarfism in d1 is due to a reduction in cell number or to shortened cell length, the cell number of the leaf sheath, the internode, the root and the lemma was compared between Nipponbare, a wild-type rice and d1-5, a d1 allele derived from Nipponbare. Our results indicate that the cell number was reduced in all organs analyzed in d1-5. In addition, cell enlargement was found in roots and lemma of d1-5, although the organ length in d1-5 was shorter than that of wild-type rice. These results suggest that rice Gα participates in cell proliferation in rice. Western blot analyses using anti-Gα antibody and RTPCR analyses indicate that Gα is mostly expressed in the developing organs. Gα promoter activity studies using the GUS reporter gene confirmed that the expression of Gα was highest in developing organs. We conclude that rice Gα participates in the regulation of cell number in a developmental stage-dependent manner.