Rhizosphere soil metagenome Metagenome

Microorganisms can improve plant resistance to drought through various mechanisms such as the production of plant hormones, osmolytes, antioxidants, and exopolysaccharides. It is, however, unclear how previous exposure to water stress affects the functional capacity of the soil microbial community to help plants resist drought. We compared two immediately adjacent soils that had either a continuous or intermittent water stress history (WSH) for almost forty years. We grew wheat in these soils and subjected it to a water stress, after which we collected the rhizosphere soil and shotgun sequenced its metagenome. Wheat growing in the soil with an intermittent WSH maintained a higher fresh biomass when subjected to water stress. Genes related to resistance to drought were more abundant in the metagenome and more prevalent, diversified, and redundant in the metagenome assembled genomes of the soil with an intermittent WSH as compared to the soil with a continuous WSH. We suggest that an intermittent WSH selects for generalists that are adapted to both low and replete water contents, and that these generalists harbor a larger repertoire of genes beneficial for life under water stress.

微生物可通过合成植物激素、渗透调节物质、抗氧化剂与胞外多糖等多种机制，提升植物的抗旱性。然而，目前尚不清楚土壤先前经历的水分胁迫，会如何影响土壤微生物群落协助植物抵御干旱的功能能力。本研究选取两块紧邻的土壤，二者分别拥有近40年的持续或间歇水分胁迫历史（water stress history, WSH）。我们在这两类土壤中种植小麦，并对小麦施加水分胁迫处理；随后收集根际土壤，通过鸟枪法测序其宏基因组（metagenome）。结果显示，在具有间歇水分胁迫历史的土壤中种植的小麦，在经受水分胁迫时能够维持更高的鲜重生物量。相较于持续水分胁迫历史的土壤，间歇水分胁迫历史土壤的宏基因组中，抗旱相关基因的丰度更高；且在其宏基因组组装基因组（metagenome assembled genomes, MAGs）中，这类基因的分布更广、多样性更强且冗余度更高。我们推测，间歇水分胁迫历史会筛选出既能适应低水分条件又能适应充足水分条件的泛化类群，且这类泛化类群携带更多有助于植物在水分胁迫下存活的功能基因。