The mitochondrialorf117Shagene desynchronizes pollen development and causes pollen abortion in the Arabidopsis Sha CMS

Abstract

AbstractCytoplasmic male sterility (CMS) is of major agronomical relevance in hybrid breeding. In gametophytic CMS, abortion of pollen is determined by the grain genotype, while in sporophytic CMS, it is determined by the mother plant genotype. While several CMS mechanisms have been dissected at the molecular level, gametophytic CMS has not been straightforwardly accessible. We used the gametophytic Sha-CMS in Arabidopsis to characterize the cause and process of pollen abortion by implementingin vivobiosensing in single pollen and mitoTALEN mutagenesis. We obtained conclusive evidence thatorf117Shais the CMS-causing gene, despite distinct characteristics from other CMS-genes. We measured thein vivocytosolic ATP content in single pollen, followed pollen development and analyzed pollen mitochondrial volume in two genotypes that differed only by the presence of theorf117Shalocus. Our results show that the Sha-CMS is not triggered by ATP deficiency. Instead, we observed desynchronization of a pollen developmental program. Pollen death occurred independently in pollen grains at diverse stages and was preceded by mitochondrial swelling. We conclude that pollen death is grain-autonomous in Sha-CMS and propose that mitochondrial permeability transition, which was previously described as a hallmark of developmental and environmental-triggered cell death programs, precedes pollen death in Sha-CMS.HighlightThe Arabidopsis CMS-causing geneorf117Shadoes not limit pollen ATP supply. Pollen-centered approaches show desynchronization of development and mitochondrial swelling before pollen death, which occurred at diverse stages.