title: Two Tightly Linked Genes at the hsa1 Locus Cause Both F1 and F2 Hybrid Sterility in Rice.
abstract: Molecular mechanisms of hybrid breakdown associated with sterility (F2 sterility) are poorly understood as compared with those of F1 hybrid sterility. Previously, we characterized three unlinked epistatic loci, hybrid sterility-a1 (hsa1), hsa2, and hsa3, responsible for the F2 sterility in a cross between Oryza sativa ssp. indica and japonica. In this study, we identified that the hsa1 locus contains two interacting genes, HSA1a and HSA1b, within a 30-kb region. HSA1a-j (japonica allele) encodes a highly conserved plant-specific domain of unknown function protein (DUF1618), whereas the indica allele (HSA1a-i(s)) has two deletion mutations that cause disruption of domain structure. The second gene, HSA1b-i(s), encodes an uncharacterized protein with some similarity to a nucleotide-binding protein. Homozygous introgression of indica HSA1a-i(s)-HSA1b-i(s) alleles into japonica showed female gamete abortion at an early mitotic stage. The fact that the recombinant haplotype HSA1a-j-HSA1b-i(s) caused semi-sterility in the heterozygous state with the HSA1a-i(s)-HSA1b-i(s) haplotype suggests that variation in the hsa1 locus is a possible cause of the wide-spectrum sterility barriers seen in F1 hybrids and successive generations in rice. We propose a simple genetic model to explain how a single causal mechanism can drive both F1 and F2 hybrid sterility.
authors.affiliation: Plant Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Department of Genetics, SOKENDAI (the Graduate University for Advanced Science), Mishima, Shizuoka 411-8540, Japan. Electronic address: takubo@nig.ac.jp.
authors.forename: Takahiko
authors.initials: T
authors.lastname: Kubo
authors.affiliation: STAY GREEN Co., Ltd., Kisarazu, Chiba 292-0818, Japan.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Takashi
authors.affiliation: Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi 464-8601, Japan.
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Ashikari
authors.affiliation: Plant Breeding Laboratory, Division of Genetics and Plant Breeding, Department of Applied Genetics and Pest Management, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yoshimura
authors.affiliation: Plant Genetics Laboratory, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan; Department of Genetics, SOKENDAI (the Graduate University for Advanced Science), Mishima, Shizuoka 411-8540, Japan. Electronic address: nkurata@nig.ac.jp.
authors.forename: Nori
authors.initials: N
authors.lastname: Kurata
mesh_terms: D000595:Amino Acid Sequence; D032461:Chromosomes, Plant / Q000235:genetics / Q000378:metabolism; D055993:Germ Cells, Plant / Q000378:metabolism; D006824:Hybridization, Genetic; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics* / Q000502:physiology; D051479:Plant Infertility; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D010940:Plant Proteins
keywords: DUF1618 protein; Oryza sativa; embryo sac abortion; epistasis; hybrid sterility