Identiifcation of a novel gain-of-function mutant allele,slr1-d5, of rice DELLA protein

Controlling the height of crops plays a crucial role for their yields. The large scale utilization of semi-dwarf varieties has greatly improved crop yield, providing an effective support for world food security. In rice, a main food for over half of the world’s population, a number of dwarf loci have been identified. However, most of them are recessive, such as the ‘green revolution’ gene sd1. To gain more beneficial loci for rice breeding programs, exploring new mutations is needed, especially the dominant loci which can be used broadly for hybrid breeding. Here, we isolated a novel dominant dwarf rice mutant, slr1-d5. All of the internodes of slr1-d5 are reduced. We find that the responsiveness of slr1-d5 to gibberellin(GA), GA3, was significantly reduced. Map-based cloning revealed that the dominant dwarfism of slr1-d5 was caused by an amino acid substitution in the N-terminal TVHYNP domain of rice DELLA protein, SLR1, where the conserved amino acid Pro(P) was substituted to His(H). Our findings not only further prove the pivotal role of TVHYNP motif in regulating SLR1 stability, but also provide a new dwarf source for improvement of rice germplasms.