Phenotype Identification And Gene Cloning Of A Rice Male Sterile Mutant Ls7

Rice(Oryza sativa L.)is one of the most important food crops in the world and a model specie for monocotyledons.The normal development of male reproductive organs is very important for higher plants to reproduce through sexual reproduction.The study of male sterile mutants in rice is helpful to reveal the molecular mechanism of male reproduction in rice,and has certain theoretical and practical significance for promoting hybrid breeding and heterosis utilization in rice.In this study,ls7(low sterility7)is a male sterile mutant with stable genetic characters obtained by screening the ethyl methylsulfone(EMS)mutation library of Ningjing 4.However,during anther development,tapetum degradation was delayed,intracellular components were abnormal,microspores in mitosis stage atrophied abnormally,pollen abortion occurred in mature stage,and outer tectum was broken discontinuously.In addition,reactive oxygen species(ROS)staining of rice anthers at different stages showed that there was no significant difference in superoxide anion between mutant LS7 anthers and wild type anthers,but the content of hydrogen peroxide decreased significantly at the later stage of anther development.These morphological analyses suggest that LS7 gene may regulate tapetum degradation by affecting ROS homeostasis at the late anther development stage of rice.The programmed cell death(PCD)of the mutant tapetum is delayed,and some sporopollen related substances can not be deposited in the outer wall of pollen normally,resulting in male sterility.In order to locate the mutated gene,a genetic segregation population was constructed.Preliminary mapping,genetic mapping,fine mapping and physical mapping were carried out.It was found that LS7 gene was located between c11-1.2.20 and c11-2.2.7 markers,and the physical distance was 179 kb.At the same time,taking male sterility as the target trait,using mutmap analysis based on high-throughput sequencing,the whole genome of extreme individuals was sequenced and compared,and a significant difference region on chromosome 11 was obtained.The gene in this region encodes an auxiliary activities family enzyme(AA family enzyme).Phenotypic identification,cytological analysis and gene mapping of mutant ls7 showed that the auxiliary activity family enzymes were the candidate genes leading to the mutation.The mutant ls7 showed male sterility,abnormal development of tapetum,Microspore and pollen wall.These results lay a foundation for further study of rice male sterile gene LS7.