Genetic characterization and fine mapping of S25, a hybrid male sterility gene, on rice chromosome 12.

Takahiko Kubo,Nori Kurata,Atsushi Yoshimura

doi:10.1266/ggs.17-00012

Takahiko Kubo, Nori Kurata + Show 1 more

Open Access

https://doi.org/10.1266/ggs.17-00012

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Abstract

Hybrid male sterility genes are important factors in creating postzygotic reproductive isolation barriers in plants. One such gene, S25, is known to cause severe transmission ratio distortion in inter-subspecific progeny of cultivated rice Oryza sativa ssp. indica and japonica. To further characterize the S25 gene, we fine-mapped and genetically characterized the S25 gene using near-isogenic lines with reciprocal genetic backgrounds. We mapped the S25 locus within the 0.67-1.02 Mb region on rice chromosome 12. Further genetic analyses revealed that S25 substantially reduced male fertility in the japonica background, but not in the indica background. In first-generation hybrid progeny, S25 had a milder effect than it had in the japonica background. These results suggest that the expression of S25 is epistatically regulated by at least one partially dominant gene present in the indica genome. This finding supports our previous studies showing that hybrid male sterility due to pollen killer genes results from epistatic interaction with other genes that are hidden in the genetic background.

Highlights

Hybridization between genetically divergent populations and species often produces hybrid offspring with reproductive abnormalities such as hybrid inviability or hybrid sterility
We found that hybrid male sterility due to S25 is epistatically regulated by other unlinked gene(s) hidden in the genetic background
This study aimed to identify the precise position of the S25 locus on rice chromosome 12 and the effects of genetic background on the S25 phenotype

Summary

Introduction

Hybridization between genetically divergent populations and species often produces hybrid offspring with reproductive abnormalities such as hybrid inviability or hybrid sterility. These phenomena play pivotal roles in speciation by acting as postzygotic reproductive isolation barriers. Duplication of genes essential for reproductive development allows subsequent loss of one copy without any reduction in fitness, and reciprocal gene loss in both species leads to hybrid sterility. This is a logical and simple mechanism that can lead to hybrid sterility.

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