College of Agriculture and Animal Husbandry, Qinghai University, Xining 810016, China.
College of Agriculture and Animal Husbandry, Qinghai University, Xining 810016, China; State Key Laboratory of Plateau Ecology and Agriculture of Qinghai University, Xining 810016, China; Key Laboratory of Use of Forage Germplasm Resources on Tibetan Plateau of Qinghai Province, Xining 810016, China.
Microbiol Res. 2024 Oct;287:127866. doi: 10.1016/j.micres.2024.127866. Epub 2024 Aug 4.
Alpine meadows, which are critical for biodiversity and ecosystem services, are increasingly degrading, necessitating effective restoration strategies. This study explored the mechanism by which Kobresia humilis, an alpine meadow-constructive species, modulates the rhizosphere microbiome via root exudates to enhance growth. Field investigations revealed that the plant height of K. humilis in a severely degraded (SD) alpine meadow was significantly higher than that in other K. humilis populations. Consequently, we analysed the differences between this plot and other K. humilis samples with different degrees of degradation to explore the reasons underlying the phenotypic differences in K. humilis. 16 S rRNA amplicon sequencing results showed that the SD plots were significantly enriched with more Bacillus, altering the composition of the rhizosphere microbial community of K. humilis. The collection and analysis of root exudates from various K. humilis locations revealed distinct differences. Procrustes analysis indicated a strong correlation between the root exudates and the rhizosphere microbiome composition of K. humilis. Model-based integration of metabolite observations, species abundance 2 (MIMOSA2), and Spearman's rank correlation coefficient analysis were used to identify the root exudates potentially related to the enrichment and recruitment of Bacillus. Bacillus from SD samples was isolated and screened, and the representative strain D334 was found to be differentially enriched compared to other samples. A series of in vitro experiments with the screened root exudates and strain D334 demonstrated that K. humilis could recruit Bacillus and promote its colonisation by releasing flavonoids, particularly baicalin. Additionally, K. humilis can release sucrose and riboflavin, which promote strain growth. Finally, soil microbiome transplantation experiments confirmed that different K. humilis phenotypes were closely related to the functions of the rhizosphere microbiome, especially in root morphological shaping. Moreover, the effects of Bacillus inoculation and the microbiome on the plant phenotypes were consistent. In summary, this study revealed a new mechanism by which K. humilis recruits rhizosphere growth-promoting bacteria and enhances soil nutrient utilisation, thereby promoting plant growth. These findings provide a theoretical basis for ecological restoration using soil microbial communities and clarify the relationship between plant metabolites and microbial community assembly.
高山草甸对于生物多样性和生态系统服务至关重要，但它们正日益退化，因此需要采取有效的恢复策略。本研究探索了高寒草甸建群种高山嵩草通过根系分泌物调节根际微生物组来促进生长的机制。野外调查显示，在严重退化（SD）高山草甸中，高山嵩草的植株高度明显高于其他高山嵩草种群。因此，我们分析了该地段与其他退化程度不同的高山嵩草样本之间的差异，以探讨高山嵩草表型差异的原因。16S rRNA 扩增子测序结果表明，SD 样地中 Bacillus 丰度显著增加，改变了高山嵩草根际微生物群落的组成。从不同高山嵩草地点采集和分析的根系分泌物存在明显差异。普罗克汝斯平移分析表明，高山嵩草根际分泌物与根际微生物群落组成之间存在很强的相关性。基于代谢物观测、物种丰度 2（MIMOSA2）和斯皮尔曼等级相关系数分析的模型整合，确定了与 Bacillus 富集和招募相关的潜在根系分泌物。从 SD 样本中分离并筛选 Bacillus，发现代表菌株 D334 与其他样本相比明显富集。用筛选出的根系分泌物和菌株 D334 进行一系列体外实验表明，高山嵩草通过释放类黄酮（特别是黄芩苷）来招募 Bacillus 并促进其定植。此外，高山嵩草可以释放蔗糖和核黄素，促进菌株生长。最后，土壤微生物组移植实验证实，不同高山嵩草表型与根际微生物组的功能密切相关，尤其是在根形态塑造方面。此外， Bacillus 接种和微生物组对植物表型的影响是一致的。综上所述，本研究揭示了高山嵩草招募根际促生细菌并增强土壤养分利用的新机制，从而促进植物生长。这些发现为利用土壤微生物群落进行生态恢复提供了理论依据，并阐明了植物代谢物与微生物群落组装之间的关系。
