Metabolite and transcript profiling of Guinea grass (Panicum maximum Jacq) response to elevated [CO₂] and temperature

Introduction: By mid-century, global atmospheric carbon dioxide concentration ([CO ₂ ]) is predicted to reach 600 μmol mol ⁻¹ with global temperatures rising by 2 °C. Rising [CO ₂ ] and temperature will alter the growth and productivity of major food and forage crops across the globe. Although the impact is expected to be greatest in tropical regions, the impact of climate-change has been poorly studied in those regions. Objectives: This experiment aimed to understand the effects of elevated [CO ₂ ] (600 μmol mol ⁻¹ ) and warming (+ 2 °C), singly and in combination, on Panicum maximum Jacq. (Guinea grass) metabolite and transcript profiles. Methods: We created a de novo assembly of the Panicum maximum transcriptome. Leaf samples were taken at two time points in the Guinea grass growing season to analyze transcriptional and metabolite profiles in plants grown at ambient and elevated [CO ₂ ] and temperature, and statistical analyses were used to integrate the data. Results: Elevated temperature altered the content of amino acids and secondary metabolites. The transcriptome of Guinea grass shows a clear time point separations, with the changes in the elevated temperature and [CO ₂ ] combination plots. Conclusion: Field transcriptomics and metabolomics revealed that elevated temperature and [CO ₂ ] result in alterations in transcript and metabolite profiles associated with environmental response, secondary metabolism and stomatal function. These metabolic responses are consistent with greater growth and leaf area production under elevated temperature and [CO ₂ ]. These results show that tropical C ₄ grasslands may have unpredicted responses to global climate change, and that warming during a cool growing season enhances growth and alleviates stress.