Yuan Ting, Ren Weibo, Wang Zhaoming, Fry Ellen L, Tang Shiming, Yin Jingjing, Zhang Jiatao, Jia Zhenyu
Inner Mongolia Key Laboratory of Grassland Ecology, School of Ecology and Environment, Inner Mongolia University, Hohhot, China.
Key Laboratory of Forage Breeding and Seed Production of Inner Mongolia, Inner Mongolia M-Grass Ecology and Environment (Group) Co., Ltd., Hohhot, China.
Front Plant Sci. 2023 Jul 6;14:1180576. doi: 10.3389/fpls.2023.1180576. eCollection 2023.
Grazing disturbance can change the structure of plant rhizosphere microbial communities and thereby alter the feedback to promote plant growth or induce plant defenses. However, little is known about how such changes occur and vary under different grazing pressures or the roles of root metabolites in altering the composition of rhizosphere microbial communities. In this study, the effects of different grazing pressures on the composition of microbial communities were investigated, and the mechanisms by which different grazing pressures changed rhizosphere microbiomes were explored with metabolomics. Grazing changed composition, functions, and co-expression networks of microbial communities. Under light grazing (LG), some saprophytic fungi, such as sp., sp., sp. and sp., were significantly enriched, whereas under heavy grazing (HG), potentially beneficial rhizobacteria, such as sp., sp., and sp., were significantly enriched. The beneficial mycorrhizal fungus sp. was significantly enriched in both LG and HG. Moreover, all enriched beneficial microorganisms were positively correlated with root metabolites, including amino acids (AAs), short-chain organic acids (SCOAs), and alkaloids. This suggests that these significantly enriched rhizosphere microbial changes may be caused by these differential root metabolites. Under LG, it is inferred that root metabolites, especially AAs such as L-Histidine, may regulate specific saprophytic fungi to participate in material transformations and the energy cycle and promote plant growth. Furthermore, to help alleviate the stress of HG and improve plant defenses, it is inferred that the root system actively regulates the synthesis of these root metabolites such as AAs, SCOAs, and alkaloids under grazing interference, and then secretes them to promote the growth of some specific plant growth-promoting rhizobacteria and fungi. To summarize, grasses can regulate beneficial microorganisms by changing root metabolites composition, and the response strategies vary under different grazing pressure in typical grassland ecosystems.
放牧干扰会改变植物根际微生物群落结构，进而改变反馈作用以促进植物生长或诱导植物防御。然而，对于这些变化如何在不同放牧压力下发生和变化，或者根代谢产物在改变根际微生物群落组成中的作用，我们知之甚少。在本研究中，我们研究了不同放牧压力对微生物群落组成的影响，并利用代谢组学方法探讨了不同放牧压力改变根际微生物群落的机制。放牧改变了微生物群落的组成、功能和共表达网络。在轻度放牧（LG）条件下，一些腐生真菌，如[具体真菌名称1]、[具体真菌名称2]、[具体真菌名称3]和[具体真菌名称4]显著富集，而在重度放牧（HG）条件下，潜在有益的根际细菌，如[具体细菌名称1]、[具体细菌名称2]和[具体细菌名称3]显著富集。有益的菌根真菌[具体真菌名称5]在LG和HG条件下均显著富集。此外，所有富集的有益微生物均与根代谢产物呈正相关，包括氨基酸（AAs）、短链有机酸（SCOAs）和生物碱。这表明这些显著富集的根际微生物变化可能是由这些不同的根代谢产物引起的。在LG条件下，推测根代谢产物，尤其是如L-组氨酸等氨基酸，可能调节特定的腐生真菌参与物质转化和能量循环，从而促进植物生长。此外，为了帮助缓解HG的压力并提高植物防御能力，推测根系在放牧干扰下会主动调节这些根代谢产物如氨基酸、短链有机酸和生物碱的合成，然后将它们分泌出来以促进一些特定的促进植物生长的根际细菌和真菌的生长。总之，在典型草原生态系统中，禾本科植物可以通过改变根代谢产物组成来调节有益微生物，且不同放牧压力下的响应策略有所不同。
