Guard Cell-Specific Metabolic Responses to Drought Stress in Maize

Understanding crop responses to drought stress is crucial for securing future agricultural productivity. Guard cells regulate transpiration and thus the yield burden under drought conditions. Therefore, the influence of repeated drought stress on the guard cell metabolome of Zea mays L. was investigated to improve our understanding of crop resilience mechanisms. A controlled greenhouse experiment with physiological evaluation and a non-targeted metabolomics approach was used to analyse unprimed and primed guard cells. Primed and unprimed maize plants showed similar overall physiological and metabolic responses to drought, with gas exchange and general metabolic patterns largely unaffected by priming. However, distinct priming effects emerged in specific metabolites. Metabolites of the alanine and aspartate pathway, as well as those of the glycine, serine and threonine pathway were less impacted by drought stress in guard cells than in mesophyll cells, suggesting the emphasis of plants to maintain stable guard cell metabolomes for functional integrity. In contrast, the increase in sugar concentrations in guard cells was similar to that in mesophyll cells, suggesting a pivotal role of sugars in guard cells during drought conditions. New insights into cell type-specific metabolic responses to drought stress will contribute to a better understanding of stress memory in maize. Enhancing guard cell resilience could help optimise water use efficiency for sustainable agricultural production under climate change conditions.