CAREER: Genomic, cellular, and physiological effects of whole genome duplications on organismal energy production

About This Grant

Understanding the genetic underpinnings of how plant cells produce energy represents a central goal in plant biology, especially in the context of crop improvement efforts. However, the connection between genes and the energy-related traits those genes encode is complicated for two primary reasons: (1) energy-related genes are spread across three separate cellular compartments (the nucleus, the chloroplasts, and the mitochondria), and (2) all plants have experienced one or more whole genome duplication events, in which the nuclear genome has been doubled or more, during their evolutionary history. Indeed, many of our most important crop species have more than two copies of their nuclear genome inside their cells. How this “genomic redundancy” affects energy production is largely unknown; however, the balance between nuclear genome copy number and the mitochondria and chloroplasts appear to be critical to plant energy production. We will employ and train students and researchers to investigate how plant cells maintain this balance. Whole genome duplication events (WGDs), in which the nuclear genome is doubled or more as a result of allopolyploidization or autopolyploidization, are a major force for plant diversification. Because the cytoplasmic genomes are separately replicated (and inherited) from the nuclear genome, the stoichiometric balance between the three genomic compartments (i.e., cytonuclear stoichiometry) is expected to be perturbed following WGD. Recent work indicates that cytonuclear stoichiometry is maintained following WGD in both monocots and eudicots, suggesting that gene dosage balance between the nuclear and cytoplasmic genomes represents an important component of polyploid lineage formation and evolution. We therefore hypothesize that cytonuclear stoichiometry is critical for establishing the cell’s chloroplast and mitochondrial content, such that variation in cytonuclear stoichiometry leads to variation in photosynthetic and respiratory performance and that the genomic architecture of cytonuclear stoichiometry is responsive to changes in nuclear genome size and content. First, we will test these hypotheses in diploid, polyploid, and aneuploid contexts by quantifying and measuring organelles, evaluating photosynthetic performance, and comparing nuclear vs. cytoplasmic transcript pools of single cells. We will also perform association tests in the Arabidopsis thaliana genome and confirm those associations with molecular knockouts to disentangle the complex genomic architecture underlying cytonuclear stoichiometry. The findings are expected to set the stage for future applied efforts aimed at improving metabolic function in polyploid crops. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.