Gene Mapping And Physiological Characteristics Analysis Of A Zebra Leaf Mutant L139 In Rice

In this study,a zebra leaf mutant(named as l139)with a phenotype of lateral yellow-green was selected from a mutant library of a japonica rice variety Shennong 9816(SN9816)subjected to ethyl methanesulfonate(EMS)mutagenesis.Used indica rice varieties Kasalath to cross with l139 to construct F2 populations for genetic analysis and gene mapping.and determined and analyzed agronomic traits,chlorophyll content,photosynthetic capacity,ultrastructure and partial gene expression of mutants and wild-types.The results were as following:1.Compared with the wild type,mutant l139 showed yellow-green striped leaves from seedling stage to tillering stage.The stripes were perpendicular to the veins,similar to the zebra stripes;from the tillering stage to the full heading stage,the yellow-green stripes gradually disappeared until they completely returned to green.2.The photosynthetic pigment measurement results showed that the SPAD value,chlorophyll a,chlorophyll b,and carotenoid content of the yellow leaves of mutant l139 were reduced by 68.6%,48.9%,51.3%,and 41.2%,respectively,compared to the wild type,making their q P,Y(II)and ETR were 78.7%,32.7%,and 78.4% lower than those of the wild type,respectively.This indicates that the mutant l139’s photosynthetic pigment synthesis is hindered,resulting in a decrease in leaf photosynthetic performance.3.Compared with the wild type,the yellow leaf part of mutant l139 had no obvious chloroplast structure and no obvious organelles in the cells.The malondialdehyde(MDA),hydrogen peroxide(H2O2)and superoxide anion(O2-)content of mutant l139 leaves were 71.4%,35.3%,and 452.1% higher than those of the wild type,respectively.This results indicated that the increased of reactive oxygen species led to the destruction of cell structure and partial apoptosis in mutant l139.4.Genetic analysis showed that the phenotype of mutant l139 was controlled by a single recessive nuclear gene.The gene mapping results showed that the mutant gene was located between the markers Indel4 and Indel6 on the long arm of chromosome 5,and this interval was about 76.95 kb.Sequencing of 16 candidate genes in this interval revealed that ORF5 had a G to A substitution on the 6th exon,which caused the amino acid to change from tryptophan to a stop codon.This gene is involved in apoptosis,proliferation,movement and adhesion of cells.5.Real-time quantitative PCR showed that gene L139 was expressed in all types of wild-type tissues,but the highest expression was found in leaves,while the expression in mutant leaves was significantly decreased.The expression of most chlorophyll synthesis genes and photosynthetic related genes in mutants was also significantly different from that in wild type.6.The plant height and effective panicle number of mutant l139 were 20.3% and 41.2% lower than those of wild type,respectively.