Genetic Analysis And Gene Mapping Of Grain Filling Low Temperature Sensitive Mutant Gfls1 In Rice

Rice(Oryza sativa L.)grain filling stage is a crucial period determining rice yield and quality,and temperature has a significant impact on rice grain filling.A sensitive grainfilling and low temperature-sensitive mutant gfls1(grain filling low temperature sensitive mutant 1)was obtained from EMS-induced mutagenesis in the Zhongzao 35(ZZ35).Through phenotypic and genetic analysis of mutant genes,and genetic mapping of gfls1 gene,the main results obtained are as follows:(1)The gfls1 mutant showed severe grain insufficiency and opaque embryo endosperm wrinkling under low temperatures during the grain filling stage.When the average temperature during the grain filling period is between 20℃ and 29℃,there is a positive correlation between the thousand grain weight of the ZZ35 and gfls1 mutants and temperature.However,the thousand grain weight of the gfls1 mutant is significantly lower than that of ZZ35,and the difference is greatest at 20℃ treatment,with a decrease of 49.79%.The plumpness of the gfls1 mutant is most significantly affected by low temperature.(2)Reduction of total starch content in grains of gfls1 mutant under low temperature,the content of linear starch increased,the content of branched starch decreased,and the content of resistant starch increased.Agronomic traits investigation showed that there was no significant difference in tiller number,panicle length,spikelet number,and seed setting rate between gfls1 mutant and ZZ35.Compared with ZZ35,plant height,thousand grain weight,and yield per plant decreased by 12%,44%,and47%,respectively.(3)Genetic analysis of the gfls1 mutant was carried out by constructing a hybrid F2 population of Fu9811/gfls1 and ZZ35/gfls1,and it was found that the phenotype(low temperature grain filling and incomplete grain filling)was controlled by a recessive nuclear gene.Using the F2 segregation population of the cross between radiation Fu9811/gfls1 to map the candidate gene,KASP molecular markers were used to locate the candidate gene between S8 and S10,with a physical distance of 142 kb.The interval contains 16 candidate genes,including 12 functionally annotated genes,one of which is the Os BEIIb(SBE3)gene encoding rice endosperm starch branching enzyme IIb.Sequencing of Os BEIIb revealed that there is a single base T deletion in exon 16 of Os BEIIb in gfls1,resulting in the premature termination of protein translation.Therefore,we speculate that Os BEIIb is the candidate gene for gfls1.(4)Using q RT-PCR to analyze the expression levels of starch synthesis and transport-related genes in the grain filling stage of ZZ35 and gfls1 mutant.It was found that under the low-temperature treatment condition of 20℃,the expression levels of starch synthesis-related genes Os AGPL1,Os AGPL2,Os AGPL3,Os AGPS1,Os AGPS2 b,Os GBSSI,Os SSIIa,Os SSIIIa,Os SBE1,Os SBE3,Os ISA1,Os ISA2,and Os PUL,as well as starch transport-related genes Os SUT1 and Os SWEET11 were significantly lower in the gfls1 mutant than in ZZ35.It indicates that the insufficient grain filling in gfls1 mutant under low temperature may be related to the inhibition of the expression of starch synthesis and transport-related genes.