Functional Investigation Of RO Controling Rice Stem Bending Growth

Rice is one of the most important food crops, and feeds about more than half of the world’s population in the world. The production of rice is directly related to the country’s food security in China. Since the plant architecture of rice is closely related to the yield and resistance, cultivation of plants with ideal plant architecture is an important direction of rice breeding, and also an important research project of developmental biology. For the exploration of plant architecture, more studies are concentrated on the plant height, and achieved a large number of research results. So far, many semi-dwarf genes have been identified. Based on the research of the dwarf mutants, many controlling factors involved in plant hormone synthesis or signal transduction and regulation pathway have been identified. However, the dwarf mechanism of rice remains to be elucidated. In addition, the reports about the bending-stem growth mutants in rice are very limited, and in-depth study is still needed. By EMS mutagenesis, we found a stem-rotated mutant at seedling stage, which also showed twisted blade, later gradually erect but dwarf stems and smaller seeds. We temporarily named it ROTATED, referred to as RO.By the method of map-based cloning, we cloned this gene, which encodesa new member of the formin protein family. IAA inhibited the expression of RO gene, and NPA, which is an auxin transport inhibitor, induced its expression. ro mutant was hypersensitive to NPA, while NPA treated wild type can mimic the stem-twisted growth phenotype of ro mutant, suggesting that RO mutation may lead to decreased polar auxin transport. FM1-43’s research indicated that ro mutant, the process of vesicular transport in ro mutant is not sensitive to BFA (inhibitor of vesicle trafficking). Meanwhile, the inhibition effect of BFA in ro mutant on rice root elongation was also not sensitive to BFA. These results suggest that vesicle trafficking may be involved in the control of rice plant architecture through regulating the polar auxin transport process. The microarray analyses of NPA treated wild-type and ro mutant showed that RO gene was directly involved in the mutant stem’s twisted and dwarf growth through some transcription factors and cell wall structural protein. The cloning and functional study of RO gene will provide molecular and theoretical basis for cultivating rice varietis with ideal plant architecture.