Data from: Soil microbial species loss affects plant biomass and survival of an introduced bacterial strain, but not inducible plant defences

- Background and Aims: Plant growth-promoting rhizobacteria (PGPR) strains can influence plant-insect interactions. However, little is known about the effect of changes in the soil bacterial community in general and especially the loss of rare soil microbes on these interactions. Here, the influence of rare soil microbe-reduction on induced systemic resistance (ISR) in a wild ecotype of Arabidopsis thaliana against the aphid Myzus persicae was investigated.
- Methods: To create a gradient of microbial abundances, soil was inoculated with a serial dilution of a microbial community and responses of Arabidopsis plants that originated from the same site as the soil microbes were tested. Plant biomass, transcription of genes involved in plant defences, and insect performance were measured. In addition, the effects of the PGPR strain Pseudomonas fluorescens SS101 on plant and insect performance were tested under influence of the various soil dilution treatments.
- Key Results: Plant biomass showed a hump-shaped relationship with soil microbial community dilution, independent of aphid or Pseudomonas treatments. Both aphid infestation and inoculation with Pseudomonas reduced plant biomass, and led to downregulation of PR1 (salicylic acid-responsive gene) and CYP79B3 (involved in synthesis of glucosinolates). Aphid performance and gene transcription were unaffected by soil dilution.
- Conclusions: Neither the loss of rare microbial species, as caused by soil dilution, nor Pseudomonas, affect the resistance of A. thaliana against M. persicae. However, both Pseudomonas survival and plant biomass respond to rare species loss. Thus, loss of rare soil microbial species can have a significant impact on both above- and belowground organisms.

- 研究背景与目的：植物促生根际菌（Plant growth-promoting rhizobacteria，PGPR）菌株可调控植物-昆虫互作，但目前学界对土壤细菌群落整体变化，尤其是稀有土壤微生物丧失对这类互作的影响仍知之甚少。本研究以野生生态型拟南芥（Arabidopsis thaliana）为实验材料，探究稀有土壤微生物丰度降低对其对抗桃蚜（Myzus persicae）的诱导系统抗性（Induced systemic resistance，ISR）的影响。
- 研究方法：为构建微生物丰度梯度，对土壤微生物群落进行梯度稀释后接种至土壤，并测试与该土壤微生物采自同一地点的拟南芥植株的响应。实验测定了植株生物量、植物防御相关基因的转录水平以及昆虫适合度；此外，还在不同土壤稀释处理条件下，测试了植物促生根际菌菌株荧光假单胞菌（Pseudomonas fluorescens）SS101对植株与昆虫适合度的影响。
- 主要结果：无论蚜虫侵染或假单胞菌接种处理如何，植株生物量与土壤微生物群落稀释梯度均呈驼峰型相关关系。蚜虫侵染与假单胞菌接种均会降低植株生物量，并导致PR1（水杨酸响应基因）与CYP79B3（参与硫代葡萄糖苷合成）的转录水平下调。但蚜虫适合度与基因转录水平均不受土壤稀释处理的影响。
- 研究结论：土壤稀释所导致的稀有微生物物种丧失，以及假单胞菌接种，均不会影响拟南芥对抗桃蚜的抗性。然而，假单胞菌的存活与植株生物量均会响应稀有物种的丧失。由此可见，稀有土壤微生物物种的丧失可对地上与地下生物均产生显著影响。