Abstract
The impact of combined heat and drought stress was investigated inArabidopsis thaliana and compared to individual stresses to
reveal additive effects and interactions. A combination of plant
metabolomics and root and rhizosphere bacterial metabarcoding were used
to unravel effects at the plant holobiont level.
Hierarchical cluster analysis of metabolomics signatures pointed out two
main clusters, one including heat and combined heat and drought, and the
second cluster that included the control and drought treatments.
Overall, phenylpropanoids and nitrogen-containing compounds, hormones
and amino acids showed the highest discriminant potential. A decrease in
alpha diversity was observed upon stress, with stress-dependent
differences in bacterial microbiota composition. The shift in
beta-diversity highlighted the pivotal enrichment ofProteobacteria , including Rhizobiales ,Enterobacteriales and Azospirillales .
The results corroborate the concept of stress interaction, where the
combined heat and drought stress is not the mere combination of the
single stresses. Intriguingly, multi-omics interpretations evidenced a
good correlation between root metabolomics and root bacterial
microbiota, indicating an orchestrated modulation of the whole
holobiont.