| Heading date is an important agronomic trait of rice(Oryza sativa L.),which determines the rice cultivation region and growing seasons.Ehd1 is a key and unique heading date gene.The expression of Ehd1 integrates different upstream signals and it regulates the expression of downstream florigen genes Hd3 a and RFT1,which directly affect the heading date.In previous work,Ehd1 transgenic silencing materials PD(DJ)and PZ(ZH11)in Japonica rice Dongjin(DJ)and Zhonghua 11(ZH11)backgroud,Ehd1 overexpression materials OEEhd1(DJ background)were obtained.Phenotypic observations showed that transgenic silencing material delayed heading,but agronomic traits were better than the wild type,while the overexpression material was the opposite.That indicate that changing the expression level of Ehd1 can affect agronomic traits.Ehd1 as the core transcriptional activator of heading.If we directly edit the exon region of Ehd1,the gene will lose its function,resulting in extreme phenotype,which is not conducive to breeding applications.In this study,the strategy of editing the regulatory region of the Ehd1 gene promoter was adopted to obtain a variety of mutants with different expression levels of Ehd1,and to select the best allelic materials from them to increase the adaptability of the rice area and achieve the purpose of rice variety improvement.In this study,the promoter of Ehd1 was analyzed.The CRISPR/Cas9 system was used to trigger Non-Homologous End Joining and Microhomologous arm-Mediated End Joining DNA repair mutation in the promoter region of Ehd1.Some promoter mutants have been obtained.In this study,through the transcriptome sequencing and analysis of the above materials,13 downstream target genes of Ehd1 in addition to Hd3 a and RFT1 were screened,candidate genes are involved in various biological processes such as stress resistance and metabolism,which provides direction and genetic resources for further studying the function of Ehd1 gene and improve the heading networkThese genes and Ehd1 have been knocked out by CRISPR/Cas9 gene editing technology,and some Ehd1 and candidate gene single mutant,double mutants have been obtained.In summary,this study fine-tune the expression of the Ehd1 gene by editing the promoter of the rice core transcription factor Ehd1,and screening the optimal heading mutants,which providing a new idea for expanding the adaptability of the rice area and improving the heading date.In addition,this study screened out 13 downstream target genes of Ehd1,which laid a firm foundation for the further study of the genetic network of Ehd1 regulating rice heading. |
