Genetic Analysis And Mapping Of Five Leaf-related Mutants In Rice (Oryza Sativa L.)

Leaf color mutants are one of the common mutant types in high plants. Gene cloning and functional analysis of leaf color mutants are important in the discovery of photosynthetic-related genes, photosynthesis regulatory mechanism, pathways of chlorophyll biosynthesis and degradation, chloroplast structure and function, and genetic breeding application. In our study, three inherited stably yellow leaf mutants, Yl-1, Yl-2and Yl-3, were isolated by EMS treating for the japonica rice variety Xiushui09dry seeds. Compared with their wild type Xiushui09, these mutants show less tiller, short culm, yellow leaf at the seedling and tilling stage. With the growth of the mutant plants, the leaves turn green. Genetic analysis showed that the yellow leaf traits of the three mutants were all controlled by one pair of recessive nuclear gene. Genetic mapping of the mutant genes were conducted using a F2mapping populations of Yl-1, Yl-2and Yl-3crossed with indica variety Zhenshan97. Gene Yl-1was mapped between SSR markers RM282and RM6080, within genetic distance of7.5cM in chromosome3. While gene Yl-2and gene Yl-3were mapped in the same site of chromosome5between5-43w and RM1237, with genetic distances of2.0cM and6.8cM to each of them, respectively.Plant photosynthetic capacity of the top three leaves have the most contribution to rice yield, among which the flag leaf contributes more than half of carbohydrate in grains during the grain filling stage. The architectural structure improvement of flag leaf is one of important objectives for plant type breeding in rice. The inherited stably double flag leaf mutant Zj88d was isolated by EMS treating for the japonica rice variety Zhejing88dry seeds. Phenotypic analysis revealed that the mutant exhibit defects between the1st and2nd internode elongation. Genetic analysis showed that the double flag leaf trait of Zj88d was controlled by one pair of recessive nuclear gene. Using map-based cloning method, the target gene was located between7-44w and RM5344within genetic distance of1.2cM or physical distance of603kb on the distal short arm of chromosome7. Screening the one hundred candidate genes in this range, it is found that the cloned gene OSH15which regulates the formation of SAM, and control the development of rice internodes included. Sequencing revealed that the double flag leaf mutant Zj88d displayed a single-base substitution (a for g) in the last nucleotide of intron2allele of OSH15. Zj88d and OSH15were thus presumptively considered to be a pair of alleles. It's expected that the specificity mutation site of Zj88d would be contribute to the emerging research area of alternative splicing in the future.Because leaves are determinate organs that serve as the main photosynthetic organ in plants, leaf morphology is also an important trait. The formation of adaxial-abaxial axis plays a crucial role in leaf development. Molecular biological studies suggest that the specification of adaxial-abaxial polarity is majorly controlled independently by the expression of some genes. By using EMS treatment, another mutant Acl-61which showed abaxially curled leaf has been found. Through our research work, the target gene Acl-61was positioned near the telomere of the short arm of rice chromosome1, in upstream of SSR marker RM1280within4.2cM or physical distance of459kb, and one hundred candidate genes involved. This result is a good foundation for the subsequent fine mapping and cloneing of Acl-61.