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New Phytol. 2019 Oct;224(1):505-517. doi: 10.1111/nph.16035. Epub 2019 Aug 1.

Genetic basis and timing of a major mating system shift in Capsella.

Author information

1
Department of Ecology, Environment and Plant Sciences, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
2
Department of Plant Biology, Swedish University of Agricultural Sciences & Linnean Center for Plant Biology, SE-750 07, Uppsala, Sweden.
3
Institut National de la Recherche Agronomique, UPR 1258, Centre National des Ressources Génomiques Végétales, 31326, Castanet-Tolosan, France.
4
Department of Botany, University of Osnabruck, 49076, Osnabrück, Germany.
5
Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo, F-59000, Lille, France.

Abstract

A crucial step in the transition from outcrossing to self-fertilization is the loss of genetic self-incompatibility (SI). In the Brassicaceae, SI involves the interaction of female and male specificity components, encoded by the genes SRK and SCR at the self-incompatibility locus (S-locus). Theory predicts that S-linked mutations, and especially dominant mutations in SCR, are likely to contribute to loss of SI. However, few studies have investigated the contribution of dominant mutations to loss of SI in wild plant species. Here, we investigate the genetic basis of loss of SI in the self-fertilizing crucifer species Capsella orientalis, by combining genetic mapping, long-read sequencing of complete S-haplotypes, gene expression analyses and controlled crosses. We show that loss of SI in C. orientalis occurred < 2.6 Mya and maps as a dominant trait to the S-locus. We identify a fixed frameshift deletion in the male specificity gene SCR and confirm loss of male SI specificity. We further identify an S-linked small RNA that is predicted to cause dominance of self-compatibility. Our results agree with predictions on the contribution of dominant S-linked mutations to loss of SI, and thus provide new insights into the molecular basis of mating system transitions.

KEYWORDS:

Capsella ; S-locus; dominance modifier; long-read sequencing; parallel evolution; plant mating system shift; self-compatibility; small RNA

PMID:
31254395
DOI:
10.1111/nph.16035

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