The laser light shed on Darwin’s ‘Abominable mystery’

Reproductive isolation is the inability of a species to breed with related species and thus is a key to evolution of new species in flowering plants. In interspecific crosses between closely related species, a stage of pollen tube reception by female tissues of the pistil act as a pivotal hybridization barrier. Within the genus Arabidopsis, pistils of Arabidopsis thaliana can be fertilized by pollen from its relative species, but about half of the ovules reject the release of sperm from heterospecific pollen tubes and these rejected pollen tubes continue growing inside the embryo sacs (referred to as pollen tube overgrowth). A loss-of function mutant line of ARTUMES gene, encoding a subunit of the oligosaccharyltransferase complex, pollinated with heterospecific pollen shows a higher overgrowth rate than the wild type, suggesting that ARTUMES is involved in interspecific pollen tube reception. However, its molecular mechanism is largely unknown. Here, we report that some knockout lines of receptor kinases show ARTUMES mutant-like impairment in interspecific pollen tube reception, indicating that these receptor kinases might be potentially the target proteins of ARTUMES. We anticipate these receptors recognize the ligands from conspecific (self) pollen and heterospecific pollen either in the presence of ARTUMES, thus they can lead successful interspecific fertilization. We also identified ARTUMES mutant shows abnormal calcium dynamics in their female tissue during pollen tube reception. In this talk, I would like to briefly mention about how mathematical modeling can be promoting to pursue the questions regarding calcium dynamics reflecting male-female communication during fertilization. We anticipate these mechanisms that enable interspecific fertilization contribute to rapid development and diversification of flowering plants in recent geological time.