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

Abstract

The current pace of crop plant optimization is insufficient to meet future demands and there is an urgent need for novel breeding strategies. It was previously shown that plants tolerate the generation of triparental polyspermy-derived plants and that polyspermy can bypass hybridization barriers. Polyspermy thus has the potential to harness previously incompatible climate adapted wild varieties for plant breeding. However, factors that influence polyspermy frequencies were not previously known. The endopeptidases ECS1 and ECS2 have been reported to prevent the attraction of supernumerary pollen tubes by cleaving the pollen tube attractant LURE1. Here we show that these genes have an earlier function that is manifested by incomplete double fertilization in plants defective for both genes. In addition to supernumerary pollen tube attraction, ecs1 ecs2 mutants exhibit a delay in synergid disintegration, are susceptible to heterofertilization, and segregate haploid plants that lack a paternal genome contribution. Our results thus uncover ECS1 and ECS2 as the first female factors triggering the induction of maternal haploids. Capitalizing on a high-throughput polyspermy assay, we in addition show that the double mutant exhibits a three-fold increase in polyspermy frequencies. As both haploid induction and polyspermy are valuable breeding aims, our results open new avenues for accelerated generation of climate adapted cultivars.

Brassinosteroids function as the plant male and female reproductive hormone coordinating gene expression

“…EC1 peptides from egg cells promote gamete fusion (21)(22) and ECA1 gametogenesis-related family proteins (23) also play a role in fertilization. RALF6/7/16/36/37 secreted from pollen tubes (24) and ECS1/2 secreted from ovules (25)(26) are involved in blocking polytubey to accomplish fertilization. ECS1/2 have also recently been shown to be involved in synergid cell degeneration (26).…”

“…RALF6/7/16/36/37 secreted from pollen tubes (24) and ECS1/2 secreted from ovules (25)(26) are involved in blocking polytubey to accomplish fertilization. ECS1/2 have also recently been shown to be involved in synergid cell degeneration (26). However, the molecular mechanisms regulating these complex male-female communications remain to be elucidated.…”