Phenotypic Characterization, Genetic Analysis, Candidate Genes Mapping And Predicting Of A Brittle Mutant In Rice

Rice (Oryza sativa L.) mechanical strength is an important agronomic trait of rice, theagronomic reflects the physical character of cell wall. Study of the mutant, which hasaltered in mechanical strength would help us to illustrate the mechanism of cell wallmaterial biosynthesize and functions of some related gene. Study of brittle gene has greatsignificance in higher yield, lodging resistance, disease resistance and resistance areas.Brittle gene in improving the utilization of straw, improving the woody cellulose contentand quality has broad application prospects. In this study, a brittle rice mutant wasidentified and the genetically analyzed, fine mapped and candidate gene cloned. The mainresults were as follows:1. A novel brittle rice mutant was isolated from the EMS-induced offspring of indicaEyou532. The fp2 mutant has an alteration in plant morphology. The fp2 has reductionin mechanism strength. The fp2 plants exhibited a semi-dwarf with shorter culm,shorter drooping leaf and a disperse phenotype compared with the wild type, fp2seedlings had much shorter hypocotyls and roots than those of wild-type.2. We have studied the fp2 and the wild-type from physical and chemistry character. Theresults showed that, the forces required to break the mutant culms was decreased to70% of that required for the wild type, the culm elongation of mutant decreas to 65% ofthat required for the wild-type. Chemical analyses indicated a decrease in cellulose andlignin content, and an increased in hemicelluloses and silicon3. We have studied the fp2 and the wild-type from cytology. Anatomical analyses showedthat the fp2 mutation caused a reduction in cell length and wall thickness, an increase incell width, an obvious alteration of cell wall structure, especial in the vessel elements,which led to a global alteration in plant morphology.4. Genetic analysis for the fp2 gene: Through investigations and genetic analysis in fourgenetic populations, as Shuhui527/ fp2, 93-11/fp2, Nipponbare/ fp2 and jing89/fp2,We found that the brittle trait of fp2 was controlled by a pair of recessive gene.5. Fining map of fp2: By Nipponbare/ fp2 F₂ population, fp2 was mapped on the long armof Chromosome 10 between the SSR makers RM271 and RM258 with the geneticdistance of 1.1cM and 11.4cM, respectively. We continue look for the new markers tomap the gene, and the gene was mapped between RM271 and RM25547 more.According the above results, the linkage map and complete sequence of the genomic among the fp2 gene were obtained from RGP. We developed some new SSR and InDelmarker to fining map the fp2 gene in the aim area, the fp2 gene was mapped betweenmarker InDel2-15 and InDel4-12 finally, the range about 69kb.6. Putative and analyzed candidate genes for fp2: We have analyzed and putative the aimsequence by TIGR Rice Browse, Rice Gaas andhttp://genes.mit.edu/GENSC-AN.html.We have get seven putative genes, LOC_Os10933040, LOC_Os10g33050,LOC_Os10g33070, LOC_Os10g33060, LOC_Os10g33080, LOC_Os10g33104,LOC_Os10g33130. The putative gene LOC_Os10g33040was associated to proteinbinding, cell wall form, protein modification process, physiological process, anatomicalstructure morphogenesis.7. We have showed that the fp2 mutation resulted in a reduction in cellulose, lignin, celllength and mechanical strength; an increase in hemicellulose, silicon and cell width; analteration in structure and thickness of cell wall and plant morphology. The fp2 genemight play a role in the regulation of dynamic changes of microfibrils during the allstages of establishment of the microfibril or other noncellulosic components depositionand array as well as during cell elongation, which in turn influences cell morphogenesis,the biosynthesis and deposition of cell wall materials, the formation of primary andsecondary cell wall, mechanism strength and plant morphology. The mechanism aboutthe decline of mechanical strength and the alteration of plant morphology in fp2 iscomplex. It was needed further elucidation the function of fp2 by gene cloning.