Cloning And Functional Researches Of Two Branch Controlling Genes In Rice

Plant architecture is an important base for rice yield formation potential and plays a critical role in highyield breeding. Ideal plant architecture needs all-round coordination among plant height, tiller(including the tiller number and the tiller angle), panicle-shaped (including the size and the length of thepanicle, the number of branches per panicle) and other factors in rice. It has an important guidance andpractical significance for the further improvement of the rice plant architecture and rice yield formationpotential, and eventually converting into production to clarify the role of the determining factors in therice plant morphogenesis.In this study, we described two branch-related mutants, named ghd10and abr1. We performed themorphological observation, genetic analysis, gene clone and expression specificity analysis of the twomutants, and studied the regulation pathway of Ghd10participate.The mutant ghd10was identified from japonica variety Wuyunjing7plants subjected to ethylmethane sulfonate (EMS) treatment. The ghd10mutants exhibited increased panicle length and primarybranch number, delayed flowering time and tall stalks. Map-based cloning and genetic complementationexperiment revealed that the point mutation of Ghd10was responsible for the phenotype of ghd10.Ghd10encoded a transcription factor with Cys-2/His-2-type zinc finger motifs. Transient expressionanalysis of the Ghd10-GFP fusion protein in tobacco mesophyll cells showed that the Ghd10-GFPprotein expressed in the nucleus. Ghd10mRNA accumulated most abundantly in developing leaves andpanicle structures, but rarely in roots. Expression analysis revealed that the expression levels of Ehd1,Hd1, RFT1, Hd3a and OsMADS15decreased dramatically under both short-day and long-dayconditions in ghd10. Overall, the cloning of Ghd10provided a rare opportunity for studying themolecular mechanisms underlying the association between panicle branches development and yieldformation. The ghd10allele was a useful resource for rice breeding to improve panicle traits in ricegrown in tropical and low-latitude areas.The novel rice mutant abr1(abnormal branching1), which showed shorter plant height, increasedtiller number and abnormal panicle branching, was identified from the Oryza sativa ssp. Japonicacultivar Nipponbare. Genetic analysis showed that ABR1was a single recessive nuclear gene.Microscopic analysis of the internode transversal and longitudinal sections showed that the cell lengthof abr1was shorter than that of the wild-type plants. Map-based cloning showed that there was a26-bpdeletion containing the splicing site of the ABR1genome sequence, which led to alternative splicing ofABR1pre-mRNA and generated multiple transcript variants in abr1. The genetic complementationexperiment revealed that the phenotype of abr1was completely restored to normal in the transgeniclines, and RNA interference experiment showed that the phenotype of RNAi transgenic line was similarwith the abr1mutant. All the experiments demonstrated that ABR1was the target gene which wasresponsible for the phenotype of abr1. The ABR1was highly expressed in culms, panicles, rachis andspikelet, which was consistent with that of the phenotype mutantion. Transient expression of the ABR1-GFP fusion protein in tobacco mesophyll cells and rice protoplast showed that the ABR1was anon-nuclear localization protein.It provided new genetic resources for further expounding the molecular mechanism of rice plantmorphogenesis to cloning of the above two genes.