Functional Analysis Of Rice Grain Shape Gene GS2.1

Rice grain shape is an important trait affecting yield and quality simultaneously.Previously,a grain shape gene GS2.1,was fine mapped in the 160.6 kb region between the molecular markers 2M-7-1 and 2M-9 on rice chromosome 2,by using the backcross population developed with the large-grain Indica rice variety TDX as the donor parent and the Japonica rice variety Nipponbare(NPB)as the recipient parent.In this study,the function of GS2.1 was verified by CRISPR/Cas9 gene editing technology and genetic complementation experiments.The and identification of resistance to rice blast,which is of great significance for the analysis of the genetic mechanism of rice grain shape and grain shape improvement of rice varieties.The GS2.1,which was encoded growth transcription factor Os GRF4,was also fund involving in the regulation of rice blast resistance.The results of this study are of great significance for the analysis of genetic mechanism of rice seed shape and grain shape improvement of rice varieties.The main results are as follows:1)The gene of GS2.1 in GS2.1-NIL,which with large grain and Nipponbare genetic background,was knock out by using CRISPR/Cas9 gene editing technology.The grain shape and other main agronomic traits of the T1 generation homozygous mutant lines,namely CR-NIL-20 and CR-NIL-23,were investigated.Compared with GS2.1-NIL,the grain length,thickness and thousand kernel weight of the gene knockout lines were significantly reduced.The grain length,thickness and thousand kernel weight were decreased by 17.59%～23.27%,2.94%～7.14% and 30.39%～32.82%,respectively.The plant height and panicle length of the knockout lines were also decreased significantly.2)There were five base variations in the CDS interval of GS2.1 between the NPB and GS2.1-NIL.The transgene lines were developed,with the Nipponbare as the recipient parent,by constructed overexpression vectors for the GS2.1 alleles in NPB and GS2.1-NIL.The grain length of the GS2.1OE-1 line,which with the Nipponbare genetic background and overexpression of the GS2.1,was significantly increased by 20.2% compared to Nipponbare.The grain length,grain width and grain thickness of the gs2.1 overexpressed lines with Nipponbare genetic background were significantly reduced by 3.3%,10.4% and 9.9%,respectively compared to Nipponbare.The results further verified that GS2.1 positively regulates the grain length and significantly increases the grain length of rice.3)The rice blast disease score were 8.7,6.1 and 3.6 of CO39,NPB and GS2.1-NIL,respectively,which grew in the rice blast disease nursery at Dawei Mountain of Liuyang City.In vitro inoculation test results showed that the lesion area and mycelia of CR-NIL-15 and NPB were significantly greater than GS2.1-NIL.The above results showed that GS2.1knockout results in reduced resistance to rice blast.