ECS1 and ECS2 regulate polyspermy and suppress the formation of haploid plants by promoting double fertilization

In flowering plants, the number of pollen tubes that provide sperm cells to the female gametes is restricted by a pollen tube block. This safeguard mechanism is only activated after successful fertilization of both female gametes and involves the disintegration of pollen tube attracting synergid cells. Yu and coworkers previously reported that the endopeptidase ECS1 and ECS2, which are secreted by fertilized egg cells, prevent the attraction of supernumerary pollen tubes by cleaving the pollen tube attractant LURE1¹. Here we report on an earlier defect in ecs1 ecs2 mutants that is manifested by single rather than double fertilization of either egg or central cell. The defect is accompanied by a delay in synergid disintegration providing an alternative explanation for the extra pollen tubes observed in the double mutant. These results are corroborated by our finding that ecs1 ecs2 plants segregate both, haploid as well as polyspermy derived triploid plants.