AtNOT1 is required for gametophyte development in Arabidopsis

In flowering plants, pollen development is under a dynamic and well-orchestrated transcriptional control, characterized by an early phase with high transcript diversity and a late post-mitotic phase skewed to a cell-type-specific transcriptome. Such transcriptional changes require a balance between synthesis and degradation of mRNA transcripts, the latter being initiated by deadenylation. The CCR4-NOT complex is the main evolutionary conserved deadenylase complex in eukaryotes, and its function is essential during germline specification in animals. We hypothesized that the CCR4-NOT complex might play a central role in mRNA turnover during microgametogenesis in Arabidopsis. Disruption of NOT1 gene, which encodes the scaffold protein of the CCR4-NOT complex, showed abnormal seed set. Genetic analysis failed to recover homozygous progeny, and reciprocal crosses confirmed reduced transmission through the male and female gametophytes. Concordantly, not1 embryo sacs showed delayed development and defects in embryogenesis. not1 pollen grains exhibited abnormal male germ unit configurations and failed to germinate. Transcriptome analysis of pollen from not1/+ mutants revealed that lack of NOT1 leads to an extensive transcriptional deregulation during microgametogenesis. Therefore, our work establishes NOT1 as an important player during gametophyte development in Arabidopsis.