A visible assay for meiotic homologous recombination in pollens of rice

Abstract

Meiotic homologous recombination generates genetic diversity for adaptations to environmental changes, and is the underlying principle of breeding by genetic crossing. Meiotic recombination in plants is solely manifested by the phenotypes of the progeny after a series of genetic crosses, and thus its assessment is laborious and time-consuming. A facile assay for meiotic recombination in higher plants, especially in crops, will innovate molecular breeding technology. In this study, we developed a fluorescence-based quantitative assay for meiotic gene conversion in rice pollens, using a pair of homologous genes: an active gene encoding cyan-fluorescent protein (CFP) as the recipient gene, and a yellow-fluorescent protein (YFP) gene without a promoter as the donor gene for the conversion. Pollens emitting YFP fluorescence, representing meiotic gene conversion products, were detected at frequencies of 2.7×10⁻⁶ to 4.9×10⁻⁵ in five transgenic lines, whereas the mitotic gene conversion rate between the two genes was less than 10⁻⁶ in calli derived from one of these lines. Southern hybridization analyses of the transgenic lines revealed that the CFP and YFP genes were integrated at various independent loci in each line. This method provides a rapid technique to assess meiotic gene conversion.