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Proc Natl Acad Sci U S A. 2010 Nov 23;107(47):20417-22. doi: 10.1073/pnas.1003124107. Epub 2010 Nov 3.

Rice pollen hybrid incompatibility caused by reciprocal gene loss of duplicated genes.

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1
Plant Genetics Laboratory, Genetic Strains Research Center, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.

Abstract

Genetic incompatibility is a barrier contributing to species isolation and is caused by genetic interactions. We made a whole genome survey of two-way interacting loci acting within the gametophyte or zygote using independence tests of marker segregations in an F(2) population from an intersubspecific cross between O. sativa subspecies indica and japonica. We detected only one reproducible interaction, and identified paralogous hybrid incompatibility genes, DOPPELGANGER1 (DPL1) and DOPPELGANGER2 (DPL2), by positional cloning. Independent disruptions of DPL1 and DPL2 occurred in indica and japonica, respectively. DPLs encode highly conserved, plant-specific small proteins (∼10 kDa) and are highly expressed in mature anther. Pollen carrying two defective DPL alleles became nonfunctional and did not germinate, suggesting an essential role for DPLs in pollen germination. Although rice has many duplicated genes resulting from ancient whole genome duplication, the origin of this gene duplication was in recent small-scale gene duplication, occurring after Oryza-Brachypodium differentiation. Comparative analyses suggested the geographic and phylogenetic distribution of these two defective alleles, showing that loss-of-function mutations of DPL1 genes emerged multiple times in indica and its wild ancestor, O. rufipogon, and that the DPL2 gene defect is specific to japonica cultivars.

PMID:
21048083
PMCID:
PMC2996679
DOI:
10.1073/pnas.1003124107
[Indexed for MEDLINE]
Free PMC Article

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