Study On Physiological, Biochemical And Molecular Mechanism Of A Green-Revertible Albino Rice Mutant Bai S

Leaves are the main places for plant photosynthetic system operation and the energy source of all higher organisms on the earth to maintain life. The abnormal leaf color of plant directly affects plant growth and development. We obtained a new green-revertible albino mutant at seedling stage in rice by artificial mutagenesis, which named bai S. In this paper, gene fine-mapping of the leaf color mutant were conducted, and the functions of the gene during chloroplast development were discussed in brief. The main results were as follows:1. The green-revertible albino mutant bai S belonged to temperature insensitive type. The albino leaf color part gradually turned green from the veins to the leaf margin. Finlly, the leaf color of bai S appeared obvious some green thread between albino blocks, which would continue to mature period, and it was lighter compare with the leaf color of wild type. Compared with wild type mutant, the chlorophyll and carotene content of bai S was significantly lower at seeding stage. The chloroplasts of bai S developed imperfect and were fewer in number and smaller in size and lamellar structure abnormal differentiation through the analysis of chloroplast ultrastructure. Therefore, the lack of chlorophyll phenomenon caused the albino phenotype of mutant.2. The mutant gene was mapped between SSR marker abl43 and Indel marker ID8 on BAC clone AP003239 of rice chromosome 1, with genetic distances of 0.11 cM and 0.06 cM, Physical distance was about 20.6kb. Four candidate genes were found in the gene mapping interval. Sequencing analysis showed that LOC-Os01g55974 gene of encoding deoxycytidylate deaminase occurred base mutation. The muant gene inserted two bases (AA) after 5807 bp base position. Accordingly, leading cDNA Code bases to frame-shift and the amino acid premature termination after the 395th. These results implied that the LOC-Os01g55974 gene might be the candidate gene of BAI S.3. The full-length of BAI S gene was 5946bp, and the gene comprised nine exons and eight introns. BAI S gene encoded a protein of 248 amino acids (the molecular weight was about 26.70kD). In the grass family, the protein sequence had a strong conservative. Phylogenetic analysis of proteins showed the sequence of protein encoded by BAI S had homoiogs with equences of proteins encoded by brachypodium distachyon and hordeum vulgare of the grass family.4. Real-time PCR analysis showed that the expression of coding photosynthesis related genes such as Cab1, Cab2 and the chloroplast transcription/translation related genes such as rpoA, rpoB, rpoTP, OsROLP were significantly reduced in the albino stage of mutant bai S, especially the expression of CabI, rpoB and rpoTP. However, their expression increased significantly when the bai S turned green. It could be speculated that the expressions levels of transcription/translation related genes in chloroplast were directly or indirectly controlled by BAI S gene in the early seedling stage of bai S. OsROLP gene was the major gene of chloroplast development in the first stage. Due to the expression of OsROLP gene was blocked in the albino stage of mutant bai S, the chloroplast development stagnated in the first stage, resulting in albino leaves.