Elevated CO2 mitigates the impact of drought stress by upregulating glucosinolate metabolism in Arabidopsis thaliana.

Elevated CO2 (eCO2) reduces the impact of drought, but the mechanisms underlying this effect remain unclear. Therefore, we used a multidisciplinary approach to investigate the interaction of drought and eCO2 in Arabidopsis thaliana leaves. Transcriptome and subsequent metabolite analyses identified a strong induction of the aliphatic glucosinolate (GL) biosynthesis as a main effect of eCO2 in drought‐stressed leaves. Transcriptome results highlighted the upregulation of ABI5 and downregulation of WRKY63 transcription factors (TF), known to enhance and inhibit the expression of genes regulating aliphatic GL biosynthesis (e.g., MYB28 and 29 TFs), respectively. In addition, eCO2 positively regulated aliphatic GL biosynthesis by MYB28/29 and increasing the accumulation of GL precursors. To test the role of GLs in the stress‐mitigating effect of eCO2, we investigated the effect of genetic perturbations of the GL biosynthesis. Overexpression of MYB28, 29 and 76 improved drought tolerance by inducing stomatal closure and maintaining plant turgor, whereas loss of cyp79f genes reduced the stress‐mitigating effect of eCO2 and decreased drought tolerance. Overall, the crucial role of GL metabolism in drought stress mitigation by eCO2 could be a beneficial trait to overcome future climate challenges. Summary Statement: Elevated CO2 can mitigate drought stress, but the underlying mechanisms remain largely unclear. This study identifies the genetic regulation of aliphatic glucosinolate by eCO2 and its role in inducing drought tolerance by improving water relations through their role in stomatal regulation. [ABSTRACT FROM AUTHOR]