Positional Cloning And Preliminary Study Of Rice Leaf Color Related Gene WSL4

Chloroplast is the only organelle that converts light energy into chemical energy in higher plants,therefore normal differentiation and development of chloroplast is very important for the lives on Earth.The main function of chloroplasts is photosynthesis and to generate ATP which is a universal energy for all organisms.ADP and PI(phosphoric acid)can combine to produce ATP.With the help of deoxynucleotide kinase(DNK),reversible phosphate group is transported and bonded with ADP,and then catalyzes the formation of ATP.In this study,we characterized a novel deoxynucleotide kinase(DNK)which is essential for chloroplast development at early leaf stage.A single base mutation in WSL4 leads to the white striped leaf(wsl)and abnormal development of chloroplast and decreased chlorophyll content.Our study provided a novel insight into the deoxynucleotide kinase(DNK)in chloroplast development in rice,and a basis for the diversity of chloroplast development mechanism.The detailed results are as follows:1)The mutant wsl4 eshabited white stripe at early seedling stage,then gradually returned to normal phenotype after the six-leaf stage.The WSL4 gene was mapped to a 22.9 kb genomic region between marker vfD521 and marker dl on the long arm of chromosome 5.Gene prediction showed that the region contains 3 opening reading frames(ORF).Sequence alignments between wild-type and wsl4 showed that there was a single nucleotide variation in the third exon of ORF3(LOC_Os05g35520),and resulted in a mutation of one amino acid in mutant WSL4 protein.WSL4 encodes a member of deoxynucleotide kinase(DNK)family,which can catalyze the reversible transporting of phosphate groups to form sugar,protein.2)Transmission electron microscopy(TEM)analysis revealed that the mutant wsl4 contains two kinds of defective chloroplasts:one had a loose chloroplast lamellae structure,and the other could not form a normal chloroplast lamellae structure.Quantitative RT-PCR indicated relative expression levels of most genes related to chloropphyll biosynthesis in mutant were downregulated.Therefore,the wsl4 affects not only chlorophyll synthesis,but also chloroplast development,eventually leading to the white stripe leaf.