Fine Mapping and Candidate Gene Analysis of the Tiller Suppression Gene <i>ts1</i> in Rice

<div><p>Tiller number is one of the key factors that influences rice plant type and yield components. In this study, an EMS-induced rice tiller suppression mutant <i>ts1</i> was characterized. Morphological and histological observations revealed that, in the <i>ts1</i> plants, the tiller buds were abnormally formed and therefore cannot outgrow into tillers. With an F2 population derived from a cross between <i>ts1</i> and an <i>indica</i> cultivar Wushansimiao, a major gene, <i>tiller suppression 1</i> (<i>ts1</i>) was fine-mapped to a 108.5 kb genomic region between markers ID8378 and SSR6884 on the short arm of rice chromosome 2. Candidate gene analysis identified nineteen putative genes. Among them, <i>ORF4</i> (LOC_Os02g01610) is a PPR gene which harbored a point mutation c.+733/C→T in <i>ts1</i> mutant plants. A co-dominant SNP marker cd-733C/T was subsequently developed and the SNP assay demonstrated that the point mutation co-segregated with tiller suppression phenotype. Quantitative RT-PCR analysis showed that the expression level of <i>ORF4</i> in <i>ts1</i> plants was significantly lower than that in their wild plants, and the expression of rice tillering regulators <i>MOC1</i> and <i>HTD1</i> was also significantly decreased in <i>ts1</i> plants. Our data indicated that <i>ORF4</i> was a strong candidate gene for <i>ts1</i> and <i>ts1</i> might play a role in regulating rice tillering through <i>MOC1</i> and <i>HTD1</i> associated pathway. The results above provide a basis for further functional characterization of <i>ts1</i> and will shed light on molecular mechanism of rice tillering. The informative SNP marker cd-733C/T will facilitate marker-assisted selection of <i>ts1</i> in rice plant type breeding.</p>