Fine Mapping and Candidate Gene Analysis of the Tiller Suppression Gene ts1 in Rice.

Lei Liu,Yanhao Shen,Fen Meng,Menghao Zhu,Zhihong Zhang,Yonggang He,Frank Alexander Feltus

doi:10.1371/journal.pone.0170574

Abstract

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 ts1 was characterized. Morphological and histological observations revealed that, in the ts1 plants, the tiller buds were abnormally formed and therefore cannot outgrow into tillers. With an F2 population derived from a cross between ts1 and an indica cultivar Wushansimiao, a major gene, tiller suppression 1 (ts1) 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, ORF4 (LOC_Os02g01610) is a PPR gene which harbored a point mutation c.+733/C→T in ts1 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 ORF4 in ts1 plants was significantly lower than that in their wild plants, and the expression of rice tillering regulators MOC1 and HTD1 was also significantly decreased in ts1 plants. Our data indicated that ORF4 was a strong candidate gene for ts1 and ts1 might play a role in regulating rice tillering through MOC1 and HTD1 associated pathway. The results above provide a basis for further functional characterization of ts1 and will shed light on molecular mechanism of rice tillering. The informative SNP marker cd-733C/T will facilitate marker-assisted selection of ts1 in rice plant type breeding.

Highlights

Rice is one of the most important cereal crops for more than half of the world’s population [1]
The results revealed that only one tiller bud of ts1 has normal morphological and histological status as compares with the wild type tiller buds, while the other tiller bud of ts1 was much smaller (Fig 1G) and had no meristem to be observed (Fig 1H)
The tiller suppression phenotype of ts1 plants could probably be attributed to the abnormal formation of their tiller buds at tillering stage

Summary

Introduction

Rice is one of the most important cereal crops for more than half of the world’s population [1]. Tiller number is considered to be one of the key factors that affects rice plant architecture and grain yield because of its involvement in determining the final number of productive panicles [2]. Desirable plant architecture which focused on tiller number has been the main goal for breeders to breed rice varieties with high-yield potential. A famous example was the “New Plant Type” rice varieties with low tiller number and large panicles, which were developed by the International Rice Research Institute [3]. For a given rice variety, its tillering ability is mainly determined by its genetic background it could be affected by environmental conditions such as light, temperature, plant density, nutrient and water supply [4].

Methods

Results

Conclusion