| Rice is one of the most important food and agricultural crops in the world.Nearly 50%of the world’s population feed on rice as the staple food.With the improvement of living standards,people have gradually increased their requirements for rice quality.The starch content in the endosperm of rice accounts for more than 90%.Therefore,in-depth study of the regulation network of starch metabolism will help to analyze the formation mechanism of rice quality.OsSGL is a gene that is induced by multiple stresses.It is located in the nucleus and contains no introns.It encodes an unknown functional protein with 255 amino acid residues and a conserved domain of DUF1645.At present,OsSGL has been reported to be involved in the growth and development and resistance of higher plants,as well as the regulation of grain length,but it’s regulation of rice quality is still unclear.In order to understand whether OsSGL is involved in the regulation of rice quality,this study first obtained OsSGL overexpression and interference materials,and found that the quality of both of them was reduced,suggesting that OsSGL is involved in the regulation of rice quality.The yeast screen library was further used to screen a sucrose synthase OsSUS1,which interacts with OsSGL.Based on this,we focused on the mechanism of OsSGL involved in regulating starch metabolism and its effect on rice quality characteristics.The main research results are as follows:1.OsSGL overexpression and interference grains are both obviously chalky,and the starch grains in the endosperm area of rice are mostly shown as round spheres of different sizes and the gaps between starch granules increase,becoming loose and not compact.The total starch and amylose content of mature seeds decreased significantly,and the protein content increased significantly.In addition,the final viscosity,minimum viscosity and recovery values of OsSGL overexpression and interference are lower than those of wild type.In terms of texture properties,the hardness of OsSGL overexpression and RNAi interference is higher than that of WT,and the viscosity is the opposite.In summary,we speculate that OsSGL plays an important role in the metabolism of endosperm starch and rice quality.2.This study analyzed the mRNA expression level of OsSGL at the filling stage,and found that OsSGL had the highest expression at 18 DAF,and selected endosperm during this period and sent it to the company for transcriptome sequencing.Transcriptome analysis showed that compared with wild-type,there were 6161 and 2460 differentially expressed genes in OsSGL-RNAi-24 and OsSGL-OE-6,respectively.Through GO enrichment pathway analysis,the two pathways of carbohydrate metabolism process and metabolic process are both enriched in OsSGL-RNAi-24 and OsSGL-OE-6,and the expression levels of genes related to starch and sucrose metabolism are analyzed.The comparison results show that,OsSGL-RNAi-24 and OsSGL-OE-6 have a very similar difference trend,and their mRNA levels are both up-regulated or down-regulated.This result is consistent with the phenotype of the decline in quality of the two.3.Through the yeast two-hybrid experiment,the interaction between OsSUS1(Sucrose synthase)and OsSGL was screened.It was further found that the 1-65 aa region at the N-terminus of OsSGL protein is the key region for interaction with OsSUS1.In addition,we also used GST Pull-down,BiFC and Co-IP experiments to confirm the interaction between OsSGL and OsSUS1.At the same time,it was found that OsSGL may realize its function by regulating the enzyme activity of OsSUS1.4.The OsSUS1-pCUbi1390Flag recombinant plasmid was further constructed,and rice was transformed with Nipponbare as a background to obtain OsSUSl overexpressing rice(OsSUS1-OE-1,OsSUS1-OE-3).The grain phenotype of OsSUS1-OE was further analyzed,and it was found that OsSUS1 was overexpressed.The increase in expressed starch content indicates that it is related to the regulation of starch metabolism. |
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