Characterization And Gene Mapping Of Yl1 Yellow Leaf Mutants In Rice

The crop yield is closely related with the LUE(light utility efficiency), the leaf color mutant is an ideal material for the study of photosynthesis in rice. In this study, the yellow-leaf mutant yl1 mutated by super rice variety YK17 was used as researching material, the phenotypic characterizations and mapped based cloning of yl1 were researched. The main research results were as follows:1) When compared the phenotype of yl1 mutant with wild type (WT) YK17, the yl1 mutant showed yellow phenotype in the stem, sheath and leaves. The phenotype traits such as plant height, the number of grain per panicle, width of flag-leaf and grain length were weaken compared with WT. Other traits such as number of tillers, length of panicle, seed setting rate,1000-grains weight, length of flag-leaf and thickness of grain almost have no difference with WT. In addition, the pollen fertility of yl1 was normal.2) Chlorophyll content in WT and yl1 mutant were detected respectively. The results indicated that the Chla level, Chlb level and total chlorophyl1 content in yl1 were significantly lower than WT YK17 at the seedling stage, and the Chlb and total chlorophyl1 content of yl1 were only one fifth and two thirds that of the WT respectively. Consistent with the seedling stage, the Chlb level in yl1 leaves was also significantly lower than that of WT at the heading stage, and the Chlb contend in yl1 was only one second that of the WT, but the Chla level of the yl1 leaves was higher than that of YK17. However, in the panicle, the Chla level, Chlb level and total chlorophyl1 content of yl1 were all lower than that of YK17 at heading stage, which might be the reason caused the yellow panicle of yl1 . When analyzing the value of Chla/Chlb, which found that the significant reduction of Chlb level was the main reason of the low total chlorophyl1 content in leaves, while the reducing of Chla and Chlb level accordingly that resulted in the lower total chlorophyl1 content in panicles. Photosynthetic characters analysis indicated that the Pn and Co were reduced in yl1 . Ultramicrostructure of chloroplasts manifested that the number of chloroplasts in yl1 was significantly less than that in WT.3) Genetic analysis and map-based cloning demonstrated that the yellow-leaf phenotype of yl1 was controlled by single recessive nuclear gene, which was finally fine mapped in a 44.8kb interval on the short arm of Chromosome 1. Bio-information analysis indicated that there were 4 ORFs in the fine mapping interval, the ORF1 (Os01g17170) encodes the Magnesium protoporphyrin IX monomethyl ester cyclase. Sequencing analysis found that there was a C to T base substitute on the 515th base in the CDS sequence of ORFl, which caused the amino acid change from serine to phenylalanine. The expression level of the ORFl in the leaves and panicles of yl1 was significantly lower than that of WT. Therefore, we concluded that the ORF1(Os01g17170) was the candidate gene of yl1 . In addition, sub-cell location analysis indicated that the YL1 protein was located in the cytoplasm.