Biological Identification And Mapping Of Floury Endorsperm Mutant Flo-c In Rice

Rice is one of the most important staple foods.The accumulation of starch and protein in endosperm directly affects the yield and quality of rice.Mining endosperm related genes and exploring the genetic and molecular mechanism of endosperm development are of great significance for understanding the formation mechanism of rice yield and quality.As one of the mutant types of endosperm,floury endosperm mutant is widely used to study the molecular regulation mechanism of endosperm development.In this study,a stable genetic mutant,floury endosperm from Changlixiang（flo-c）,was obtained from EMS mutant library of Northeast high generation japonica breeding line,Changlixiang（breeding no.Jida2015-56,WT）,and its biological characteristics were identified.The genetic analysis and gene location of flo-c were carried out by Mut Map technology using F₂population crossed between flo-c mutant and WT,and the differentially expressed genes（DEGs）between flo-c mutant and WT were analyzed by transcriptome sequencing technology.Finally,six candidate genes for FLO-C were identified by joint analysis of Mut Map and transcriptome sequencing.All these results preliminarily revealed the reason of the formation of floury endosperm characters and identified its candidate genes.The main results are as follows:1.The phenotype of the mutant flo-c was different from that of the reported mutants,and its plant type was not significantly different from the WT,but the grain was white and opaque.The aleurone layer on the cross section of brown rice was transparent,the center and periphery of mutant endosperm were irregular and loosely packed with spherical polyhedral starch granules.During the filling stage,in flo-c mutant compared to WT,the starch granules in the amyloplast were fewer and irregular in shape,and the starch granules developed slowly.The amylose content,gelatinization temperature and protein content of the mutant were not significantly different with WT.However,the RVA characteristics,starch granule surface area,quantity,and volume were significantly lower than WT,and the contents of glutenin and gliadin were also significantly lower than WT.Based on these,we speculate that FLO-C gene may be involved in starch metabolic pathway and storage protein synthesis and processing.2.The floury endosperm character of the mutant flo-c was controlled by a single recessive gene.The FLO-C gene was located on the genomic region of 8759715 bp and 11190396 bp on chromosome 10 by Mut Map analysis.This target linkage region does not overlap with the reported endosperm related genes,indicating that FLO-C is a novel gene locus controlling floury endosperm trait.Through the comparative analysis of SNP loci,37 candidate genes were screened out.3.Comparing flo-c mutant and WT,there were many DEGs in endosperm than leaves,with a total of 3227 DEGs in endosperm and 522in leaves,indicating that the formation of floury endosperm is a complex physiological metabolic process.4.Through the joint analysis of MutMap and transcriptome analysis,six candidate genes of FLO-C were identified.These genes include UDP glucuronosyl and UDP glucosyltransferase domain containing proteins（LOC＿Os10g17489）,FAD binding family protein oxidoreductase（LOC＿Os10g17780）,containing remorin C-terminal domain containing protein（LOC＿Os10g17790）,C2H2 zinc finger protein（LOC＿Os10g18364）,dehydration stress inducing protein（LOC＿Os10g21790）and leucine rich repeat family protein（LOC＿Os10g21800）.