Microbial biodiversity and structure in soil affects the composition of pyrrolizidine alkaloids in Jacobaea vulgaris

Secondary metabolites like pyrrolizidine alkaloids (PAs) act as defense compounds against aboveground and belowground attackers. We studied to get a better understanding of relevance of microbial diversity in the rhizosphere for plant growth and behavior, specifically related to secondary metabolites production. We made soil dilution to compare the composition of soil microbial communities of soil suspension, incubation and rhizosphere soil by 16s rRNA high throughput pyrosequencing, as a consequence, to determine the effects on plant behaviors. The dilution procedure leads to reduction of the diversity of bacteria at the phylum level. After regrown, the structure of microbial community in the rhizosphere changed significantly as compared to the composition in the incubated soil. Jacobeae vulgaris as model plants growing in the soil where microbial diversity were decreased, had a higher biomass and higher amount of free base form of PAs' production, which indicates the reduction of soil microbial community in the rhizosphere shows significant feedback. Our study adds evidence that soil microbes may play a role in the evolution of plant secondary metabolites in plants.

吡咯里西啶生物碱（pyrrolizidine alkaloids, PAs）这类次生代谢物，可作为防御化合物抵御植物地上与地下的侵袭者。本研究旨在深入理解根际微生物多样性对植物生长与生理行为的关联作用，特别是其与次生代谢物合成的相关性。我们通过土壤稀释梯度实验，采用16S核糖体RNA（16S rRNA）高通量焦磷酸测序技术，对比土壤悬浮液、培养土壤与根际土壤的微生物群落组成，进而明确其对植物行为的影响。该稀释流程会导致细菌在门水平上的多样性降低。待菌群复育后，根际微生物群落结构与培养土壤中的群落组成相比，发生了显著变化。以普通千里光（Jacobaea vulgaris）作为模式植物，将其种植在微生物多样性降低的土壤中，结果显示其生物量更高，游离碱型PAs的合成量也更多，这表明根际土壤微生物群落的减少会产生显著的反馈效应。本研究为土壤微生物可能参与植物次生代谢物的演化过程提供了新的佐证。