Genetic Mapping and Characterization of a Stunted Growth Mutant in Rice (Oryza sativa L.)

Abstract

We identified a stunted growth mutant from a japonica rice cultivar, Samgwang, treated with N-methyl-N-nitrosourea (MNU). The mutant showed dwarf, narrow leaf and sterile panicle. The retardation growth of the mutant initiated at the seedling stage and became severe at the reproductive stage. The plant height was reduced by 34% compared to that in wild type and showed significantly decreased first four internode length. The width of flag leaf was reduced by 46% in mutant compared with wild type. Anatomical analysis of leaves suggested that less number of the vascular bundles and epidermal cells caused narrow leaf. Also, mutant plants showed low pollen viability and complete sterility. Genetic analysis indicated that the mutation was controlled by a single recessive gene. The F2 generations of a cross between mutant and Milyang23 were used for mapping. Candidate region was detected to a short arm of chromosome 5 near the marker S05000 and S05032 via BSA method. The mutant was fine-mapped at an interval of 84kb flanked by the markers NC0501.48 and NdC0501.56. Sequencing of the region identified that the mutant carries 11bp insertion in the third exon of LOC_Os05g03550, a gene which contains two SANT domains related to histone deacetylation. The insertion led to premature stop codon in coding sequence. Quantitative RT-PCR analyses revealed that in wild type, the transcripts of LOC_Os05g03550 were constitutively expressed during whole growth period with gradual increase. Accordingly, a novel gene that cause inhibition of plant growth was isolated and the results may provide a basis for functional studies of the gene associated with growth and development of rice.