Mapping Cloning And Characteristics Analysis Of Rice Lesion Resembling Disease Mutant Lrd25

Rice lesion resembling disease mutants are a kind of mutants spontaneously formed in rice leaves without biological or abiotic stress,which are similar to local cell necrosis caused by pathogen infection.Their phenotype is similar to the symptoms of plant autoimmune reaction,and they are ideal materials for studying the mechanism of PCD and defense response in plants.In this study,photosynthetic function indexes,reactive oxygen species,panicle traits and rice quality traits were analyzed by using lrd25 mutant and SN9816 as test materials,and gene mapping of lrd25 mutant was carried out.The main research results are as follows:1.Phenotype of lesion resembling disease mutant lrd25: In the natural conditions of the field,the disease spot phenotype appears from the seedling stage,and along with the whole growth period,it is yellow strip disease spot at the beginning,and gradually changes to reddish-brown disease spot at the later stage with the development of leaves.Compared with the wild-type SN9816,the plant height of lrd25 was significantly reduced by 10.46%,and tiller number had no significant difference.Blade length was significantly decreased by19.50%,blade width was significantly increased by 16.77%.2.Photosynthetic function of lesion resembling disease mutant lrd25: Compared with the wild-type SN9816,the chlorophyll content of mutant lrd25 was significantly decreased.The chloroplast ultrastructure was also different.Compared with the wild type,the chloroplast was more obvious in the mesophyll cells of the mutant without the disease spots,and the lamellar structure could still be observed.However,the cell wall of the mesophyll cells of the mutant with the disease spots was broken,and the chloroplast was degraded seriously.Compared with the wild type,the net photosynthetic rate of the mutant decreased by 10% and transpiration rate increased by 5.93%,indicating that the mutant gene affected the chloroplast structure,and thus affected the photosynthesis of leaves.3.Reactive oxygen species(ROS)content of lrd25 mutant: Compared with the wild-type SN9816,the activities of ROS scavenging enzymes such as superoxide dismutase(SOD)and peroxidase(POD)in mutant lrd25 were extremely significantly increased,while the activities of catalase(CAT)were extremely significantly decreased.Compared with the wild type,malondialdehyde(MDA)content of the mutant was significantly increased,presumably because of the excessive ROS in the plant,resulting in a large number of cell death.4.Panicle characters of the lesion resembling disease mutant lrd25: Compared with the wild type SN9816,the panicle length,panicle weight,panicle grain number,full grain number and seed-setting rate of lrd25 were significantly decreased,but there was no significant difference in 1000-grain weight.5.Rice quality traits of the lesion resembling disease mutant lrd25: Compared with the wild type SN9816,the brown rice percentage and white rice percentage of mutant lrd25 were significantly decreased,while the protein content and amylose content increased,and the taste value decreased but did not reach the significant level.6.Gene mapping of lesion resembling disease mutant lrd25: The mutant gene LRD25 was mapped by using the method of map-based cloning,and finally the gene was located on chromosome 6 with a range of about 114 kb.The candidate genes in this region were analyzed and sequenced,and it was found that single base G on CDS of OFR10 mutated into A,and alanine mutated into threonine.