Fine mapping and cloning of MT1, a novel allele of D10

Rice tillering is an important determinant for grain production. To investigate the mechanism of tillering, we characterized a multiple tillering mutant (mt1) identified from the japonica variety, Zhonghua 11, treated with EMS. This mutant exhibits advanced tillering development and dwarfed compared with wild-type plants. Genetic analysis and fine gene mapping indicated that the mt1 mutant was controlled by a recessive gene, residing on a 29-kb window on AP003376 of chromosome 1. One putative gene in this region, encoding a carotenoid cleavage dioxygenase 8 (CCD8), was allelic to D10. The mt1 mutant phenotype was complemented by introduction of wild-type MT1, and knockdown of MT1 in wild-type rice mimicked the mutant phenotype. Real-time PCR analysis indicated that the MT1 gene is expressed highly in stems and at a low level in axillary buds, panicles, leaves, and roots. In addition, MT1 expression is clearly under feedback regulation.