Identification Of Wheat Endosperm-Specific Expressed Genes And Preliminary Analysis Of Their Promoter Elements

Wheat(Triticum aestivum L.)is an important food crop in the world,providing protein and energy for 35 % of the world’s population.Endosperm is the main nutrient storage organ of wheat,which determines the final yield and nutritional value of the grain.For a long time,wheat breeding has been devoted to increasing yield and neglecting the improvement of quality.With wheat genomic information and engineering tools development,the improvement of wheat grain quality and nutrition through bioengineering technology has become a promising method.The endosperm-specific expressed promoters can drive the specific expression of the target gene in the endosperm,and they are important tools in grain genetic engineering.However,the identification and research of endosperm-specific expressed genes and promoters are not enough in wheat due to the limitation of hexaploid characteristics and genetic transformation efficiency.In this study,we screened and annotated wheat endosperm-specific expressed genes from the published hexaploid wheat transcriptome data(http://www.wheat-expression.com/)of IWGSC,and analyzed the sequence characteristics of their promoters.The following conclusions are obtained:1.316 wheat endosperm-specific expressed genes of grain filling stage(20 days-post anthesis)were screened.The expression patterns of 18 genes were verified.Functional annotations indicated that these genes mainly involved in the accumulation of storage proteins,defense response and signal transduction,including 118 storage protein coding genes,57 defense-related genes and 30 signal transduction-related genes.The accumulation of storage protein is a highly specific and active physiological process in the endosperm.2.In the early stage of endosperm development,low molecular weight glutenins and albumins accumulate rapidly.At this time,the insulin-like growth factor 1 receptor(IGF1R)involved in sugar signal transduction is identified.A large number of gliadins and globulins accumulate during the middle stage of filling,and the signal transduction of glutamate and ABA is more active at this time.3.The promoter elements statistics of storage proteins coding genes,defense genes and signal transduction genes revealed that the expression of these genes is regulated by the light-responsive elements G-box and box-4 as well as dehydration response element DRE-core.The difference is that endosperm-specific expressed elements O2-site,GCN4＿motif and Prolamin-box are significantly riched in storage protein coding genes.The ABRE element is significantly enriched in defense genes,and the RY-element and gibberellin response elements P-box and TATC-box are significantly enriched in signal transduction genes.4.This study provides 20 candidate promoters for grain genetic engineering that can be used to improve grain quality and nutrition at particular developmental stage.Among them,the cloned three endosperm-specific promoters with high expression level have the potential to direct the expression of target genes at specific stage of endosperm development,providing an important reference for grain genetic engineering.This study not only deepens our understanding of wheat endosperm development by exploring wheat endosperm-specific expressed genes and their promoters,but also provides key information for analyzing the regulation mechanism of grain development.At the same time,it also provides an important foundation for the targeted improvement of grain quality and nutritional composition by genetic engineering.