Rice domestication from the view of seed shattering genes

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There are two cultivated rice species, Oryza sativa L. and O.glaberrima Steud. O.sativa is believed to be domesticated from a wild species, O.rufipogon Griff., whereas O.glaberrima has been differentiated probably from O.barthii Chev. et Roehr. Seed shattering habit is one of the most important traits for rice domestication. Therefore, the genes involved in seed shattering arc analyzed to elucidate the process of rice domestication. The project focused on a gene, Shattering3(Sh3), because the preliminary study revealed that Sh3 commonly existed in A-genome wild relatives of rice. The project consists of two parts : (1)Map-based cloning of Sh3 and (2)Clarification of the process of rice domestication.In the item (1),high-resolution mapping allowed us to narrow the genomic region of Sh3 to less than 5kb. There is one candidate ORF predicted in that region. However, transformation and sequencing analyses revealed that the ORF was not Sh3. We reviewed die results thoroughly and continuing … More the experiment.In the item (2),linkage mapping revealed that all of the wild species tested possessed Sh3. While O.glaberrima retains a functional Sh3 allele, it also carries a recessive sh9(iSh3) gene. The homozygotes for the recessive sh9 showed non-shattering despite of the background of functional Sh3. High-resolution mapping of Sh3 and sh9 showed that these two genes are tightly linked but on different loci. Moreover, O.glaberrima has the nucleotide change that potentially cause a premature stop codon in the ORF appeared in (1). This suggested that the ORF is a likely candidate of Sh9.The results of this project are summarized as follows :-:Loss-of-function of Sh3 was tightly related with rice domestication.-:Non-shattering O.glaberrima retains a functional Sh3 allele.-:sh9 gene tightly linked to Sh3 was identified. Loss-of-function of sh9 may be a possible cause of the domestication of O.glaberrima.We envision isolating Sh3 and sh9 to clarify the mechanism of rice domestication in the nucleotide level. Less