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Mol Plant. 2016 Feb 1;9(2):221-232. doi: 10.1016/j.molp.2015.09.014. Epub 2015 Oct 9.

Two Tightly Linked Genes at the hsa1 Locus Cause Both F1 and F2 Hybrid Sterility in Rice.

Author information

1
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.
2
STAY GREEN Co., Ltd., Kisarazu, Chiba 292-0818, Japan.
3
Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi 464-8601, Japan.
4
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.
5
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.

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.

KEYWORDS:

DUF1618 protein; Oryza sativa; embryo sac abortion; epistasis; hybrid sterility

PMID:
26455463
DOI:
10.1016/j.molp.2015.09.014
[Indexed for MEDLINE]
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