Genetic Mapping Of Two Genes Which Determine Panicle Development In Rice

Rice panicle morphology is an important agronomic trait which affect rice yield. Therefore, the study of rice panicle development has a strong influence on improving rice yield. In this research, we identified five mutants from our T-DNA insertion mutant library of the japonica rice varity Zhonghua11,ps1(panicle size1, ps1-1,ps1-2, ps1-3) and Igpl (lax grain panicle1) and pdml (panicle development mutant1). The psl mutant exhibited a dwarf, panicle length shortened about25%, primary and secondary branch number reduced33%and80%, respectively, and deviant seed size. The lgp1mutant has a umbrella-liked lax grain panicle. The pdml mutant displayed a dwarf, shortened panicle length, reduced primary and secondary branch number, reduced seeds setting rate.Co-segregation analysis of T-DNA tag with mutant phenotype confirmed that these five mutants phenotypes were not due to T-DNA insertion in the genome. Taking map-based cloning approach to locate the five genes. F2mapping populations were generated by hybrids between the five homozygous mutant and indica rice varity Zhenshan97. The segregation ratio of wild-type and mutants obey3:1Mendel ratio, indicated that these five mutants traits were controlled by a single recessive gene, respectively. Genetic mapping result indicated that ps1-1gene was located between molecular markers IN44and IN50on the short arm of chromosome11, within physical distance about105kb; And PDM1gene was located between molecular markers HL CAPS2and RM16on the short arm of chromosome3, within physical distance about85kb through massive planting F2mapping population and developing newly molecular makers. There is no molecular makers linked with phenotypes of LGP1gene by BSA method. ps1-2,ps1-3gene have the same linked molecular makers as ps1-1gene.The candidate gene of the mapping region were predicted through website of TIGR. The results of gene expression level and compared sequencing data suggested that SP1gene has4bp deletion might be the candidate gene of PS1in this study; OHK4(Oryza sativa Histidine Kinase4) gene which encode a rice histidine kinase as a cytokinin receptors has a single base mutation might be the candidate gene of PDM1in this study.Co-segregation analysis indicated that PDM1gene was co-segregation with mutant phenotypes. Result of semi-RT-PCR indicated PS1gene was mainly expressed in youth panicle and has a relative lower expression level in mature panicle. PDM1gene is a constitutive expression gene which expressed in root, leaf sheath, young leaf, mature leaf, SAM, and panicles. And has a relative lower expression level in the muture tissue such as mature leaf and mature panicle.SEM (Scanning Electron Microscope) experiments were applied to different panicle development stages of wild-type and ps1-1and pdml. There is no difference between WT and PS1in the formation of primary and secondary primordia and spikelets primordia. But PS1mutant has a defect in the elongation and development of primary and secondary branch by stereo microscope. There is no difference between WT and pdml in the formation of primary and secondary primordia, spikelets primordia, spikelets development, floral primordia.Complementary vector of PDM1gene has been constructed, and was transferred into pdml calli by Agrobacterium mediated transformation. The follow-up work is still in progress. This study will support evidence for further cloning PS1gene and in-depth research on rice panicle size development, also will lay a foundation for further cloning PDM1gene and panicle development research.