Hybrid male sterility in rice controlled by interaction between divergent alleles of two adjacent genes

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-12, Vol.105 (48), p.18871-18876
• Main Authors: Long, Yunming, Zhao, Lifeng, Niu, Baixiao, Su, Jing, Wu, Hao, Chen, Yuanling, Zhang, Qunyu, Guo, Jingxin, Zhuang, Chuxiong, Mei, Mantong, Xia, Jixing, Wang, Lan, Wu, Haibin, Liu, Yao-Guang
• Format: Article
• Language: English
• Subjects: Alleles; allelic interaction; Amino Acid Sequence; Biological Sciences; Breeding; Chimera - genetics; Cultivars; Evolutionary genetics; Freshwater; gene interaction; Gene loci; genes; Genes, Plant; Genetic loci; Genotype; Haplotypes; hybrid male sterility; Hybridity; Hybridization; loci; Male infertility; Microspores; Molecular Sequence Data; Oryza - genetics; Oryza sativa; Phenotype; plant fertility; Plant Infertility - genetics; Plant interaction; Plant populations; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants, Genetically Modified; Pollen; Pollen - genetics; Pollen - ultrastructure; protein-protein interactions; Proteins; Rice; Sequence Alignment; Two-Hybrid System Techniques
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0810108105

Sterility is common in hybrids between divergent populations, such as the indica and japonica subspecies of Asian cultivated rice (Oryza sativa). Although multiple loci for plant hybrid sterility have been identified, it remains unknown how alleles of the loci interact at the molecular level. Here we show that a locus for indica-japonica hybrid male sterility, Sa, comprises two adjacent genes, SaM and SaF, encoding a small ubiquitin-like modifier E3 ligase-like protein and an F-box protein, respectively. Most indica cultivars contain a haplotype SaM⁺SaF⁺, whereas all japonica cultivars have SaM⁻SaF⁻ that diverged by nucleotide variations in wild rice. Male semi-sterility in this heterozygous complex locus is caused by abortion of pollen carrying SaM⁻. This allele-specific gamete elimination results from a selective interaction of SaF⁺ with SaM⁻, a truncated protein, but not with SaM⁺ because of the presence of an inhibitory domain, although SaM⁺ is required for this male sterility. Lack of any one of the three alleles in recombinant plants does not produce male sterility. We propose a two-gene/three-component interaction model for this hybrid male sterility system. The findings have implications for overcoming male sterility in inter-subspecific hybrid rice breeding.