Identification Of A Ds-tagged Awned Rice Mutant And Cloning Of Related Genes

Awn is the sharp projection of the lemma in the gramineous plants. As the common structure in the wild rice species, awn can help seed dispersal, and prevent birds or animals from eating. But it is eliminated as a trait bad for harvest in the artificial selection and seed selection. Just like other crop plants, cultivated rice (Oryza sativa) is considered to be domesticated from its wild progenitor over a long time. It will be profoundly meaningful to understand the molecular mechanism behind the domestication process by identifying the functions of awnness genes. Moreover, to clone genes related to the rice awnness, and then analyze their functions in the awn development are also important when the practical significance is concerned with improvement of rice cultivars. In this study, Ds-tagged rice awnness mutant was characterized morphologically and physiologically with an objective to provide a clue to the mechanism of the rice awn development, and accumulate evidence for the phylogeny of Oryza L. Two main aspects are contained in this study:1. Morphological and physiological characterization of the awned rice mutant. By using the 53 plants randomly chosen from each population of mutants and wild-types, some morphological and physiological comparisons of the Ds-tagged mutant with wild-type rice plants were made based on measurements of plant height, tiller number and awn length.The results showed that there is significant difference between the mutant and the wild-types in plant height, tiller number and awn length. The plant height of wild-type is 70.35±3.80 cm, compared with 90.54±4.67 cm in the mutant. The tiller number of wild-type is 18.19±4.52, while the mutant has 13.68±2.50. There are no awns in the wide-type rice, but awn are distributed in the Ds-tagged rice mutants. The awn length ranged from 0.2 cm to 3.7 cm, and the average is 1.3 cm. In addition, the Ds-tagged rice mutants have weaker seed germination than wide-type rice.2. Amplification of Ds-flanking sequence and structural and functional prediction of the Ds-tagged gene. The Ds-flanking sequence was cloned from this mutant by using TAIL-PCR amplification technique. The sequenced Ds-flanking sequence was used as a query to perform an online search for homologous sequence against nucleotide sequence database by NCBI-BLAST. The Ds insertion site and the chromosomal localization of Ds-tagged gene were analyzed, and the structure and putative function of Ds-tagged gene were predicted by bioinformatics methods.The results indicated that Ds element was inserted 1339 bp upstream of the rice predicted gene Os07g0588700 of rice chromosome 7. The structure of the gene was predicted by using software of FGENESH and GeneMark.hmm, respectively, and showed highly similar in the number, size and location of exons within the gene. Moreover, the product encoded by the gene was predicted by NCBI Entrez server and Pfam. It was revealed that the deduced product was a member of rice C2H2-type zinc finger protein family, having one zinc finger domain CX₂CX₃FX₅LX₂HX₃H and QALGGH conservative region.Take the morphological, physiological and molecular comparisons as a whole, we preliminarily draw a conclusion that the Ds insertion affects the express and regulation of the zinc protein, and eventually cause awned rice.