A dwarfing mutant caused by deactivation function of alpha subunit of the heterotrimeric G-protein in rice

Abstract

Dwarf mutants in plants are crucial for elucidating regulatory mechanisms for plant growth and development. Previous studies suggested that the heterotrimeric G-protein alpha subunit known as D1/RGA1 in rice was involved in deactivation function of the G protein. However, so far no partner has been analyzed the spatial structure change acting with D1. In this study, a dwarf mutant designated Mu101 was obtained in M2 population of rice indica cultivar M804 treated with 60Co γ-ray. Genetic analysis of Mu101 indicated that the dwarf phenotype was controlled by a single dwarf gene, and the dwarf mutant was insensitive to gibberellin (GA), which was named dwarf 89 (d89). Using a large F2 population derived from a cross between the d89 and a japonica rice variety, Taigeng16, the D89 gene was fine mapped into a 62.13 kb physical distance on chromosome 5, where eight open reading frames were predicted. Sequence analysis indicated that only one bp substitution (A-G) was found in LOC_Os05g26890 between M804 and the d89 mutant. The rice GA insensitive dwarf mutant DWARF1 gene was in this locus. The modeling analysis showed amino acid threonine to alanine mutation was likely to make the alpha helix short, and led to the G protein deactivation.