RESUMEN
In the long-term growth process, alfalfa rhizosphere forms specific microbiome to provide nutrition for its growth and development. However, the effects of different perennial alfalfa cultivars on changes in the rhizosphere soil characteristics and microbiome are not well understood. In this study, 12 perennial alfalfa cultivars were grown continuously for eight years. Rhizosphere samples were tested using Illumina sequencing of the 16S rRNA gene coupled with co-occurrence network analysis to explore the relationship between alfalfa (biomass and crude protein content), soil properties, and the microbial composition and diversity. Redundancy analysis showed SOC and pH had the greatest impact on the composition of the rhizosphere microbial community. Moreover, microbial diversity also contributes to microbial composition. Soil properties (AP, EC, SOC and pH) exhibited a significant positive correlation with soil bacterial communities, which was attributed to the differences between plant cultivars. Partial least squares path modeling (PLS-PM) revealed that microbial biomass and community composition rather than diversity, are the dominant determinants in the rhizosphere soil nitrogen content of perennial alfalfa. Our findings demonstrate that the soil microbial biomass and composition of rhizosphere bacterial communities are strongly affected by cultivar, driving the changes in soil nitrogen content, and variances in the selective capacities of plants.
RESUMEN
Phosphorus is one of the essential macronutrients required by plant growth and development, but phosphate resources are finite and diminishing rapidly because of the huge need in global agriculture. In this study, 11 genes were found in the Phosphate Transporter 1 (PHT1) family of Medicago truncatula. Seven genes of the PHT1 family were available by qRT-PCR. Most of them were expressed in roots, and almost all genes were induced by low-phosphate stress in the nodule. The expression of MtPT6 was relatively high in nodules and induced by low-phosphate stress. The fusion expression of MtPT6 promoter-GUS gene in M. truncatula suggested that the expression of MtPT6 was induced in roots and nodules by phosphate starvation. In roots, MtPT6 was mainly expressed in vascular tissue and tips, and it was also expressed in cortex under low-phosphate stress; in nodules, it was mainly expressed in vascular bundles, cortical cells, and fixation zone cells. MtPT6 had a close relationship with other PHT1 family members according to amino acid alignment and phylogenetic analysis. Subcellular localization analysis in tobacco revealed that MtPT6 protein was localized to the plasma membrane. The heterologous expression of MtPT6 in Arabidopsis knockout mutants of pht1.1 and pht1.4 made seedlings more susceptible to arsenate treatment, and the phosphate concentrations in pht1.1 were higher in high phosphate condition by expressing MtPT6. We conclude that MtPT6 is a typical phosphate transporter gene and can promote phosphate acquisition efficiency of plants.