Macrotranscriptome-based rhizosphere soil microbial community composition and functional diversity in the desert shrublands of Ningxia

Metatranscriptomic sequencing analysis was conducted on four typical legume shrub rhizosphere soil samples from the Ningxia Baijitan Desert Nature Reserve to investigate the composition of functional microbial communities and the expression characteristics of functional genes in the rhizosphere soil of desert shrubs, and to explore potential stress-resistant and growth-promoting functional genes. The results demonstrated significant differences in active bacterial communities in the rhizosphere soil of the four shrubs. The relative abundance of Actinobacteria, Chloroflexi, and Acidobacteria in the rhizosphere soil of Caragana spp., Ammopiptanthus mongolicus, and Oxytropis aciphylla was significantly higher than that of Caraganatibetica. In comparison, the relative abundance of the Proteobacteria, Pseudomonas, was significantly lower than that of C. tibetica. The functional annotation of the Cluster of Orthologous Groups of Proteins indicated that the functional pathways with significant differences among groups included energy generation and conversion, cytoskeleton, etc. The results of the Kyoto Encyclopedia of Genes and Genomes functional notes demonstrated that the relative abundance of genes related to amino acid metabolism, coenzyme metabolism, and vitamin metabolism pathways in the rhizosphere soil of C. tibetica was significantly higher than those of the other three shrub soils. The transcriptional activities of proX and proW genes encoding osmoregulatory substances, kdpB and NhaA genes encoding reverse transport system, iaaM, and kynU genes encoding indoleacetic acid (IAA) synthesis, and gcd genes encoding phosphorus solubilization were significantly higher in C. tibetica rhizosphere soil than those of the other three soils. Redundancy analysis showed that Actinobacteria and Proteobacteria were positively correlated with total nitrogen (TN) and available phosphorus (AP), while Chloroflexi were significantly negatively correlated with soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), and available potassium (AK). The abundance of functional genes involved in transcription and nucleic acid metabolism was positively correlated with TP, and the abundance of genes involved in xenobiotic biodegradation and metabolism was positively correlated with TN. The result can provide a theoretical basis for further exploration of the relationship between the structure and function of soil microbial communities in specific desertification habitats and lay a foundation for enriching microbial and gene resources in desert areas.