| Screening rice mutants is an important means to study the process of rice development and regulation.Map-based cloning and functional analysis of rice mutant genes are of great significance for understanding the physiological metabolic pathway of rice and identifying new key factors participating in these pathways.In this study,the floury endosperm mutant b140 and the dwarf mutant C11 were obtained separately by chemical mutagenesis and radiation.The phenotype analysis and mapping of the mutant genes were performed.The main results are as follows:1-The b140 endosperm was floury.The grain width,grain thickness and 1000-grain weight of b140 grains were significantly lower than those of the wild type.Scanning electron microscopy showed that the starch granules in the b140 endosperm showed round or irregular shape compared to those in the wild type,with loose package.2.The total starch content and amylose content of b140 mature grains were significantly lower than those of wild type,about 94%and 91%of wild type,respectively.The soluble sugar contents of b140 mature grains were significantly higher than those of wild type.The content of glucose was 28.1%higher than that of wild type,the content of fructose increased by 84.6%and the sucrose content increased by 195.0%.3.The b140 mutant gene was finally mapped to a region about 56Kb between markers k2 and k4 on Chromosome 1 using 950 recessive individuals and new molecular markers.There are eight predicted open reading frames in this region,where the gene Os01g0179400 has been reported to affect the development of the amyloplast.Sequencing results revealed that this gene in b140 had a mutation(C to T)in the 13th exon of the coding region,leading to the substitution of proline(CCG)to serine(TCG).4.The expression level of starch synthesis genes was analyzed in endosperm of b140 and wild-type at 6,9 and 12 days after flowering(DAF)by qRT-PCR.The results showed that the expression of starch synthesis gene of b140 was lower than that of wild type.The expressing discrepancy of SSⅡb,BEⅠ,BEⅡa,GBSSⅡ,ISA3 were the largest between b140 and wild type at 9 DAF,and the expressing discrepancy of SSⅠ,SSⅡa,SSⅢ,BEⅡb,GBSS Ⅰ,AGPL2 and AGPS2b were greatest at 12 DAF.5.The relative activity of ADP-glucosepyrophosphorylase(AGPase)and UDP-glucosepyrophosphorylase(UGPase)was measured in the developing grains at 9DAF.The results showed that the activity of AGPase in mutant was significantly lower than that in wild type,while the activity of UGPase was slightly lower than that of wild type.In conclusion,b140 caused a decrease in the expression of starch synthesis genes in endosperm,and the activity of AGPase was significantly lower than that of wild type,suggesting that Os01g0179400 might affect the biosynthesis of starch.6.The rice dwarf mutant C11 was obtained from radiation of the indica cultivar Guichaoerhao.C11 showed dwarfism at tillering and maturation stages.No significant changes were observed in grain length,grain width and grain thickness of C11,but the 1000-grain weight was remarkably reduced.7.Each internode of C11 was significantly shorter than that of the wild type.C11 was classified as the dn-type dwarf mutant.8.After treatment with different gradient concentrations of GA and BR,C11 responded normally for both hormones,and we speculated that C11 was not a mutant in GA and BR signaling pathways.9.The number of vascular bundles of C11 was significantly lower than that of wild type using the cross sections of the first internode,which might be the reason for thinner stem of C11.10.The mutant gene was preliminarily located between the markers A82 and cmh6 on the long arm of chromosome 1 through the map-based cloning.The physical distance of this region was 1080Kb. |
