Background

Asian cultivated rice (Oryza sativa L.) comprises two subspecies, O. sativa subsp. indica and subsp. japonica, and the hybrids between them display strong heterosis. However, hybrid sterility (HS) limits practical use of the heterosis between these two subspecies. S5 is a major-effect locus controlling the HS of female gametes in rice, consisting of three closely-linked genes ORF3, ORF4 and ORF5 that act as a killer-protector system. The HS effects of S5 are inconsistent for different genetic backgrounds, indicating the existence of interacting genes within the genome.

Results

In the present study, the S5-interacting genes (SIG) and their effects on HS were analyzed by studying the hybrid progeny between an indica rice, Dular (DL) and a japonica rice, Balilla^ORF5+ (BL^ORF5+), with a transgenic ORF5+ allele. Four interacting quantitative trait loci (QTL): qSIG3.1, qSIG3.2, qSIG6.1, and qSIG12.1, were genetically mapped. To analyze the effect of each interacting locus, four near-isogenic lines (NILs) were developed. The effect of each specific locus was investigated while the other three loci were kept DL homozygous (DL/DL). Of the four loci, qSIG3.1 was the SIG with the greatest effects in which the DL allele was completely dominant. Furthermore, the DL allele displayed incomplete dominance at qSIG3.2, qSIG6.1, and qSIG12.1. qSIG3.1 will be the first choice for further fine-mapping.

Conclusions

Four S5-interacting QTL were identified by genetic mapping and the effect of each locus was analyzed using advanced backcrossed NILs. The present study will facilitate elucidation of the molecular mechanism of rice HS caused by S5. Additionally, it would provide the basis to explore the origin and differentiation of cultivated rice, having practical significance for inter-subspecific hybrid rice breeding programs.

中文翻译：

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调控水稻杂种不育的S5相互作用基因的遗传分析

背景

亚洲栽培稻（Oryza sativa L.）包含两个亚种：O。sativa亚种。d和亚种。粳稻，它们之间的杂种表现出很强的杂种优势。但是，杂交不育（HS）限制了这两个亚种之间杂种优势的实际应用。S5是控制水稻中雌配子HS的主要作用基因座，由三个紧密相连的基因ORF3，ORF4和ORF5组成，起着杀手-保护器的作用。S5的HS效应对于不同的遗传背景是不一致的，表明基因组中存在相互作用的基因。

结果

在本研究中，S5 -interacting基因（SIG）和它们对HS效应通过研究一个之间的杂交后代分析籼稻大米，Dular（DL）和粳稻大米，巴利拉^{ORF5 +}（BL ^{ORF5 +}），具有转基因ORF5 +等位基因。四个相互作用的数量特征位点（QTL）：qSIG3.1，qSIG3.2，qSIG6.1和qSIG12.1进行了基因定位。为了分析每个相互作用位点的影响，开发了四个近等基因系（NIL）。在保持其他三个基因座DL纯合性（DL / DL）的同时，研究了每个特定基因座的作用。在四个基因座中，qSIG3.1是在DL等位基因完全占优势的情况下效果最大的SIG。此外，DL等位基因在qSIG3.2，qSIG6.1和qSIG12.1处显示不完全的优势。qSIG3.1将是进行进一步精细映射的首选。

结论

通过遗传作图鉴定了四个与S5相互作用的QTL，并使用先进的回交NIL分析了每个基因座的作用。本研究将有助于阐明S5引起的水稻HS的分子机制。另外，它为探索栽培稻的起源和分化提供了基础，对于亚种间杂交水稻育种计划具有现实意义。