Dynamic interplay among soil nutrients, rhizosphere metabolites, and microbes shape drought and heat stress responses in summer maize

The frequent occurrence of extreme weather events has brought forth significant challenges to the future development of agriculture, and it is imperative to enhance crop resilience to extreme events. In this study, the 16S rRNA sequences and internal transcribed spacers were examined, and non-targeted metabolomics was conducted to characterize variations in summer maize crop rhizosphere microbial diversity and metabolites under drought (DS), heat (HS), and combined drought and heat stress (DHS). After 15 days of beginning stress, plants treated with DHS exhibited a 51.7% reduction in aboveground biomass and 34.5% reduction in root biomass compared to the control. Further, under DHS, Gemmatimonadota had a greater relative abundance in contrast to when exposed to either DS or HS, under DS, Actinobacteriota (16.1%) had the highest relative abundances. When exposed to HS in contrast to the other two stress treatments, the Basidiomycota (31.2%) relative abundance became significantly elevated. Metabolites, consisting of phenol ethers, fatty acyls, organooxygen compounds, allyl-type 1,3-dipolar organic molecules and organic nitro compounds, were differentially abundant across different treatments. Pathway analysis highlighted the up-regulation of ABC transporters, penicillin/cephalosporin biosynthesis, and valine/leucine/isoleucine biosynthesis pathways when exposed to either DHS compared to DS or HS. Overall, these findings suggest that DHS would stimulate the secretion of L-valine by the roots, thereby facilitating the recruitment of Gemmatimonadota and improving nitrate and ammonium absorption by roots under DHS. In brief, the results offer significant insights into the interactions between microbes and plants, as well as the potential to harness beneficial microbial communities to improve maize resilience and productivity under different types of abiotic stress.