Localization And Cloning Of Low Tiller Gene LT1 In Rice (Oryza Sativa L.)

Rice is an important food crop for mankind and feeds more than one third of the world’s population.Tillering and panicle branching are key factors to determine plant architecture and rice yield.Discovering relevant mutants,gene mapping and cloning the target genes will be beneficial to understand the molecular mechanism.And it has important theoretical significance for cultivating high yield and good quality rice varieties.In the study,we obtained a low tiller mutant,named It1 from the indica cultivar Shuhui 527(SH527)treated with ethylmethane sulfonate(EMS).The It1 mutant produced fewer tillers in its whole life stage.Compared with the wild type,the lt1 mutant displayed thicker culms,longer and wider leaves,longer panicles,reduced primary branches,secondary brancihes and number of grains per panicle,bigger grain and increased 1000-grain weight.In addition,the It1 mutant produced abnormal florets which contained extra lemma-like organs or degenerated paleae.Genetic analysis revealed that the mutant traits were controlled by a recessive single gene.Using map cloning method,the LT1 gene was narrowed to a physical interval of about 153 kb between the markers X4 and X6 on the chromosome 6,which contained 20 open reading frames.Using the qRT-PCR,two candidate genes LOC_Os06g40780/MOC1 and LOC_Os06g40840 exhibited lower expression levels in both tiller buds and young panicles of the It1 mutant than that of the wild type,respectively.These findings suggested that LOC_Os06g40780/MOC1 or LOC_Os06g40840 may be responsible for the lt1 mutant phenotypes,In this study,the mutated phenotypes including decreased tillers and panicle branches,and enlarged grains were novel in the It1 mutant.The expression analysis of several genes related to rice tillering,panicle branching,cell cycle and expansion also supported pleiotropic phenotype defects in the It1 mutant.These results will provide an abundant theoretical foundation for fine mapping and cloning the LT1 gene and contribute to the further elucidation of the molecular mechanism for tillering and panicle branching in rice.