Overexpression Of ZmDWF4 Increases Maize Yield

Plant hormones regulate plant growth and development.Plant sterol hormones include phytosterol and BRs(Brassinosteoids).Brassinosteoids,an important plant hormone,regulate many processes in plant growth and development.DWF4(CYP90B1),encoding C-22 hydroxylase,can affect the development of agronomic traits of plants by regulating the levels of endogenous BR.Maize(Zea mays L.)is an important grain and feed crop,and a crop with the largest area in China.In the early study,using Agrobacterium-mediated genetic transformation technology,we obtained three stable overexpressed ZmDWF4 transgenic plants L100,L166,L225.Here,using the three transgenic lines with excellent agronomic traits to do 27 high productive crosscombinations,we analyzed the effect of ZmDWF4 overexpression in maize hybrids.The results and conclusions are as follows:(1)By Western Blotting and hormone assay,it was further confirmed that the target gene was highly expressed in the overexpressed transgenic lines.(2)Overexpression of ZmDWF4 can promote seed development.The kernels size,kernel number per ear,grain weight and ear weight were all increased in transgenic lines compared to the wild type Qi 319.The kernels number of ear significantly increased by 15% on average.The ear weight in transgenic lines L100,L166 and L225 was increased by 42.7%,19.2% and 12%,respectively,compared to that in the wild type.(3)Overexpression of ZmDWF4 can promote the high expression levels of the response genes and transport genes of nitrate nitrogen and can promote the absorption of nitrate nitrogen in transgenic lines.(4)Overexpression of ZmDWF4 can promote the transgenic lines development.At the seedling stage,the transgenic lines developed more vigorous than the wild type.At the adult stage,the agronomic traits were improved in transgenic lines.The transgenic lines showed increased leaf number,the ear leaf area,and thephotosynthetic capacity.(5)The leaf wide-genome expression profiles data showed 301 different expression genes including 161 up-regulated expression and 140 down-regulated expression in the transgenic line L100 and wild type Qi 319 inbred.The significant GO enrichment mainly showed cell,development and growth related terms and light related terms.Through transcript profile analysis in seeds at 10 days after pollination,we identified a total of 463 differentially expressed genes,and of them,272 were upregulated,and 191 were downregulated.Transcriptome data in seeds of 15 days after pollination showed 675 differentially expressed genes,and of them,437 were upregulated,and 238 were downregulated.The functional cluster analysis of different expression genes demonstrated that they were mainly involved in cell metabolism in two RNA-seq data,especially the expression of starch and protein synthesis genes that were increased compared to the wild type.(6)Overexpression of ZmDWF4 can improve the hybrid yield traits,and increase the hybrid yield.By analysis of plot experiments,transgenic hybrids were increased by 17.25% on average compared to wild type hybrids.Taken together,the expression of ZmDWF4 can increase the BRs level to regulate development and metabolism-related gene expression,which can improve the agronomic traits of transgenic plants,and increase the yield of hybrid.The study provides a useful biotechnology strategy for the genetic improvement and further breeding of maize.