PNNL

Abstract

Phosphorus (P) limitation in plants creates a variety of metabolic perturbations that decrease photosynthesis and growth. Phosphorus limitation is especially challenging for the production of bioenergy feedstock plantation species, such as poplar (Populus spp.), where fertilization may not be practically or economically feasible. While the phenotypic effects of P limitation are well known, the molecular mechanisms underlying whole-plant and tissue-specific responses to P limitation, and in particular the responses of commercially valuable hardwoods, are less studied. To fill this knowledge gap, we used a multi-tissue and multi-omics approach using transcriptomic, proteomic, and metabolomic analyses of the leaves and roots of P-limited Populus trichocarpa (P. trichocarpa) seedlings. As expected, P-limited plants had reduced dry biomass, altered chlorophyll fluorescence, and reduced tissue P concentrations. In line with these observations, in the transcriptome of the P-limited plants, growth, C metabolism, and photosynthesis pathways were downregulated. Transcriptomics data suggested the molecular mechanisms by which poplar seedlings altered their root-to-shoot carbon allocation. Additionally, we found evidence of lipid remodeling in the leaves, which we hypothesize is the mechanism of the observed differences between leaf and root tissue P concentrations. With the notable exception of the KEGG pathway for Starch and Sucrose Metabolism (map00500), the responses of the transcriptome and the metabolome to P limitation were consistent with one another. Interestingly, no significant changes in the proteome were detected in response to P limitation. Collectively, our multi-omic and multi-tissue approach enabled the identification of important metabolic and regulatory pathways regulated across tissues at the molecular level that will be important avenues for future research.