Interactive drought and nitrogen stress produce non-additive effects on root exudates, rhizosphere microbiota and soil respiration

In this study, the rhizosphere bacterial communities of wheat (Triticum aestivum cv. RB07) were profiled using high-throughput sequencing of the 16S rRNA gene. The researchers targeted the V4 hypervariable region using the 515F/806R primer set, which was then sequenced on an Illumina MiSeq platform. To ensure high-quality biological data, raw reads were processed in the publication through the DADA2 pipeline, allowing for the identification of exact Amplicon Sequence Variants (ASVs) rather than broader OTU clusters. After removing chimeric sequences and non-bacterial reads - specifically those originating from chloroplasts and mitochondria - the data were taxonomically assigned using the SILVA v.138 database. To maintain statistical rigour and account for varying sequencing depths, all samples were standardised by rarefying to a depth of 6,500 sequences per sample. Raw reads are provided here.The analysis revealed that environmental stressors significantly altered the diversity and structure of the rhizosphere microbiota, though the effects varied over time. At the conclusion of the drought phase (T0), bacterial richness was markedly lower in drought-affected plants, whereas those under low nitrogen (WLN) conditions exhibited the highest number of ASVs. However, these differences in richness dissipated by the recovery point (T14), suggesting that the total number of taxa could stabilise following rewatering. Despite this recovery in richness, beta-diversity analysis showed that the actual composition of the communities remained distinct. Nitrogen limitation emerged as the most influential environmental filter, consistently explaining a larger proportion of community variation than drought across both time points.Crucially, the study demonstrated that the combined application of drought and nitrogen stress produced non-additive effects on the microbiome. At the recovery stage, a significant statistical interaction between these two stressors was identified, proving that the combined legacy of water and nutrient limitation restructures the rhizosphere in a way that is not predictable by studying each stressor in isolation. These shifts in the microbial community were closely mirrored by changes in root exudate chemistry, suggesting a tight coupling between plant physiological stress and the assembly of the rhizosphere microbiome. The sequencing data, which provide a window into these complex interactions, have been deposited in the NCBI Sequence Read Archive (SRA) for further analysis. Please look up the publication Interactive drought and nitrogen stress produce non-additive effects on root exudates, rhizosphere microbiota and soil respiration for other associated data.