Guard cell metabolism – A key for regulating drought resilience?

Abstract

In view of increasing drought frequencies due to climate change, enhancing grapevine resilience to water scarcity has become vital for sustainable viticulture. This study examines drought adaptation strategies in grapevine guard cells, which regulate water loss. We compared the grapevine guard cell metabolome with maize guard cells under comparable controlled drought conditions. Physiological and metabolomic analyses were conducted using mesophyll and guard cells under single and repeated drought stress conditions. Guard cells were isolated using a blending technique. An untargeted metabolic profiling was performed by using GC-MS.

Grapevine guard cells exhibited stable amino acid and sugar profiles, while maize guard cells showed dynamic sugar accumulation. These responses illustrate two contrasting strategies, namely a muted acclimation of grapevine and a vigorous acclimation of maize in mesophyll and guard cells. In both crops, metabolite concentrations were less impacted by drought stress in guard cells compared to mesophyll cells, suggesting the emphasis of plants to maintain stable guard cell metabolomes for functional integrity. Furthermore, supplemental sulfate promoted enhanced metabolic adjustments in mesophyll cells under drought conditions, while the effect of supplemental sulfate in guard cells was markedly diminished. Despite their contrasting drought strategies, grapevine and maize exhibited similar responses to supplemental sulfate. This suggests that sulfate fertilization could be a viable strategy to improve the resilience of grapevines to drought stress. In conclusion, this study identified the contrasting drought adaptation strategies of grapevine and maize, highlighting the critical role of guard cell metabolic stability in maintaining functional integrity under drought conditions.