Multi-Omics characterization of Maize pollen during storage

Abstract

Pollen is a defining feature of flowering plants and contributes to the reproductive success of many key agricultural crops. Decades of genetic and molecular research have contributed to our understanding of pollen morphology and development. While orthodox (e.g., Lamiaceae) pollen types may survive in a desiccated state for months, most recalcitrant (e.g., Poaceae) pollen types are known to exhibit short timeframes of viability. PowerPollen® has recently developed novel proprietary technology to facilitate removing grass pollens from the natural pollination system and keep pollen viable under storage until pollination is needed. An outstanding question in the field is what molecular changes occur within pollen after maturation and before death. To determine if altered metabolic and/or gene expression profiles are associated with maize pollen viability we performed global metabolomics, proteomics and phosphoproteomics of fresh maize pollen at maturity and under storage conditions known to prolong viability. To assess phenotypic differences in gene expression patterns associated with maize inbreds we also profiled two unrelated inbred genotypes with three technical replicates. In total, 969 metabolite peaks, 7,946 protein groups, 11,502 phosphorylation sites, and 3,253 phosphoproteins were identified between inbred genotypes and across storage treatments. Differential expression of the metabolomic analysis included metabolites classified into amino acids, fatty acids, sugars, sterols, and other organic acids. Differential expression of the proteomic and phosphoproteomic analyses revealed a functional skew toward protein synthesis/degradation, autophagy, carbohydrate and energy metabolism, cell wall metabolism, and cytoskeleton dynamics. This study enhances our understanding of pollen biology and will advance our understanding of molecular factors that contribute to reproductive success.