Rice Pollen Hybrid Incompatibility Caused by Reciprocal Gene Loss of Duplicated Genes

Genetic incompatibility brought about by genetic interactions is one of the hindrances to species isolation. Yoko Mizuta and colleagues at the National Institute of Genetics, Japan conducted a whole genetic makeup survey of two–way interacting locations in the zygote of an F2 population from a cross between Oryza sativa subspecies indica and japonica. They detected only one interaction that can generate an offspring, and identified two genes at different chromosomal locations that have structural similarities-DOPPELGANGER1 (DPL1) and DOPPELGANGER2 (DPL2) through positional cloning. Disruption of DPL1 occurred in indica, and DPL2 disruption occurred in japonica. DPLs code for highly conservative, plant-specific plant proteins that are very evident in the mature anther. Pollen with disrupted genes become nonfunctional, which may imply that the gene have important functions in pollen germination.

The study suggests that the source of this gene duplication was in recent small-scale duplication that occurred in the differentiation of Oryza and Brachypodium. Based on comparative analyses, it was justified that the loss of function mutations of DPL1 genes occurred several times in indica and its wild ancestor O. rufipogon, while DPL2 gene disruption is specific to japonica cultivars.

Visit http://www.pnas.org/content/107/47/20417 to read the open-access article released by the Proceedings of the National Academy of Sciences of the United States of America.