Abstract
Identification of genes responsible for barriers to gene flow between two species provides insight into molecular mechanisms of reproductive isolation. Asian cultivated rice, Oryza sativa has diverged subspecies, indica and japonica. Inter-subspecific crosses between them exhibit various hybrid incompatibilities, however the mechanisms are still largely unknown. We identified DOPPELGANGER (DPL) 1 and DPL2 that are paralogous genes, as a pair of causal genes of reproductive isolation between indica cv. Kasalath and japonica cv. Nipponbare. DPLs encode highly conserved plant specific proteins, and are strongly expressed in mature anther. Expression analysis and complementation test indicated that both DPL1 Kasalath allele and DPL2 Nipponbare allele lost their function. The pollen carrying these two defective alleles together did not germinate, suggesting an essential role of DPL in pollen germination. Evolutionary time points of DPL duplication and disruption of each allele were estimated by sequence comparison of DPL genes of 42 angiosperm species and 43 accessions/varieties of Oryza (Mizuta et al., 2010).
