Metabolomic Responses of Guard Cells and Mesophyll Cells to Bicarbonate

Abstract

Anthropogenic CO2 presently at 400 ppm is expected to reach 550 ppm in 2050, an increment expected to affect plant growth and productivity. Paired stomatal guard cells (GCs) are the gate-way for water, CO2, and pathogen, while mesophyll cells (MCs) represent the bulk cell-type of green leaves mainly for photosynthesis. We used the two different cell types, i.e., GCs and MCs from canola (Brassica napus) to profile metabolomic changes upon increased CO2 through supplementation with bicarbonate (HCO3 -). Two metabolomics platforms enabled quantification of 268 metabolites in a time-course study to reveal short-term responses. The HCO3 - responsive metabolomes of the cell types differed in their responsiveness. The MCs demonstrated increased amino acids, phenylpropanoids, redox metabolites, auxins and cytokinins, all of which were decreased in GCs in response to HCO3 -. In addition, the GCs showed differential increases of primary C-metabolites, N-metabolites (e.g., purines and amino acids), and defense-responsive pathways (e.g., alkaloids, phenolics, and flavonoids) as compared to the MCs, indicating differential C/N homeostasis in the cell-types. The metabolomics results provide insights into plant responses and crop productivity under future climatic changes where elevated CO2 conditions are to take center-stage.

Jasmonate‐mediated stomatal closure under elevated CO2 revealed by time‐resolved metabolomics

“…Global climate change and anthropogenic CO 2 emissions have posed immense challenges to plant life. Although metabolomic studies of plant single cell‐types are still rare, the importance of uncovering molecular processes at cellular or subcellular resolution has become obvious (Dai and Chen, ; Misra et al ., ). Using modern metabolomics platforms, we have shown the capabilities of MS‐based approaches in capturing guard cell metabolomic changes in response to elevated CO 2 in a time‐resolved manner, which led to identification and quantification of 358 metabolites in guard cells (at different MSI levels).…”

GENERAL CONTROL NONREPRESSIBLE4 Degrades 14-3-3 and the RIN4 Complex to Regulate Stomatal Aperture with Implications on Nonhost Disease Resistance and Drought Tolerance

“…Plants were sprayed with either 4.0 3 10 7 cfu/mL P. syringae pv tabaci or P. syringae pv tomato (DC3000) in water containing 0.025% Silwet L-77 or with water containing 0.025% Silwet L-77 as mock. Guard cell enrichment was done as described with slight modification (Misra et al, 2015). Ten grams of leaves with main veins removed was harvested and blended four times for 20 s each in 100 mL of cold sterile distilled water with the transcription inhibitors cordycepin (0.01%) and actinomycin D (0.0033%) using a Waring Laboratory Blender (http://www.waringlab.com/).…”

Metabolomics for understanding stomatal movements

“…Regarding primary metabolism, constant increase of malate was observed across the experiment in NaHCO 3 treated guard cells. Additionally, in these cells increases in fructose, glucose, and mannose were observed at the early time-points (Misra et al 2015b).…”

“…For instance, changes in the metabolite profile in response to increases in CO 2 concentration was investigated over time. For this propose mesophyll and guard cells protoplasts from B. napus were fed with sodium bicarbonate (NaHCO 3 ) (Misra et al 2015b). In this study, targeted metabolite profiling in untreated and NaHCO3 treated mesophyll and guard cell was performed using LC-MRM-MS and GC-MS/MS based technologies, in order to identify 268 metabolites related to both, primary and secondary metabolism.…”

“…LC-MS and GC-MS-based metabolomics studies have provided important information regarding the guard cell response to ABA, bicarbonate, and sucrose (Daloso et al 2015;Jin et al 2013;Medeiros et al 2018b;Misra et al 2015b;Zhu and Assmann 2017). Furthermore, the establishment of a methodology to perform 13 C-feeding experiments with the use of labelled substrates resolve a long debate regarding the role of sucrose for guard cell regulation and the mode of CO 2 fixation found in guard cells (Daloso et al 2015;Medeiros et al 2018b).…”