Cloning And Functional Analysis Of OsGatB Controlling Root Development In Rice (Oryza Sativa)

Plants roots development is of plasticity in response to environmental conditions. Nitrogen (N) is one of the most important nutrients for plant growth. In this study, a mutant with reduced root length was isolated in rice from an Ethyl-methyl sulfonate (EMS) mutant library. At 10-day-old seedling stage, the mutant exhibits about 40% shorter primary root length than the wild type (WT) plants. The mutant root length reduces 70% compared to WT under N-starvation condition, indicating that the mutant is sensitive to N-starvation. The plants of the mutant showed less tiller number, panicle number and seeds per panicle compared to WT plants.Genetic analysis indicated that the mutant phenotype is controlled by a single recessive gene. The mutated gene was detected on chromosome 11 within 73kb region between STSllgl9271k and STSllg19344k by map-based cloning. Sequencing analysis revealed that a point mutation occurred in the forth exon of the gene OsGatB (LOC_Osllg34210). The point mutation results in proline-to-leucine change in the GatB_N domain of the gene product. OsGatB is a subunit of tRNA-dependent amidotransferase GatCAB. Glu-tRNAGln is converted into Gln-tRNAGln by the GatCAB in plant mitochondria, which is important to translation of protein in mitochondria.Overexpression of OsGatB in the Osgatb mutant can rescue the mutation phenotype which confirm that the mutation phenotype is caused by the point mutation of OsGatB. quantitative PCR analysis showed that OsGatB transcriptional level is not change in the mutant remarkable. The root of mutant decreased compared to induced of WT root is not changed transcription of the gene under N-starvation by quantitative PCR analysis.Alignment of the cDNA with the genomic DNA sequences revealed that OsGatB contains 7 introns and 8 exons. Analysis for conserved domains of OsGatB indicated that the OsGatB contains two conserved domains, Gat_N and GatB_Yqey, both of them are important to the function of OsGatB. Alignment of amino acids showed that the protein is highly conserved from archaea to plants, and the mutant proline is conserved point in rice GatB.