Metabolomics and Proteomics of Brassica napus Guard Cells in Response to Low CO(2)

Stomatal guard cell response to various stimuli is an important process that balances plant carbon dioxide (CO(2)) uptake and water transpiration. Elevated CO(2) induces stomatal closure, while low CO(2) promotes stomatal opening. The signaling process of elevated CO(2) induced stomatal closure has been extensively studied in recent years. However, the mechanism of low CO(2) induced stomatal opening is not fully understood. Here we report metabolomic and proteomic responses of Brassica napus guard cells to low CO(2) using hyphenated mass spectrometry technologies. A total of 411 metabolites and 1397 proteins were quantified in a time-course study of low CO(2) effects. Metabolites and proteins that exhibited significant changes are overrepresented in fatty acid metabolism, starch and sucrose metabolism, glycolysis and redox regulation. Concomitantly, multiple hormones that promote stomatal opening increased in response to low CO(2). Interestingly, jasmonic acid precursors were diverted to a branch pathway of traumatic acid biosynthesis. These results indicate that the low CO(2) response is mediated by a complex crosstalk between different phytohormones.