Arid Land Research Center, Tottori University, Tottori 680-0001, Japan.
Institute of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
Sci Total Environ. 2023 Nov 15;899:165524. doi: 10.1016/j.scitotenv.2023.165524. Epub 2023 Jul 17.
Dryland ecosystems experience seasonal cycles of severe drought and moderate precipitation. Desert plants may develop symbiotic relationships with root endophytic microbes to survive under the repeated wet and extremely dry conditions. Although community coalescence has been found in many systems, the colonization by functional microbes and its relationship to seasonal transitions in arid regions are not well understood. Here we examined root endophytic microbial taxa, and their traits in relation to their root colonization, during the dry and wet seasons in a hot desert of the southwestern United States. We used high-throughput DNA sequencing of 16S rRNA and internal transcribed spacer gene profiling of five desert shrubs, and analyzed the seasonal change in endophytic microbial lineages. Goodness of fit to the neutral community model in relationship to microbial traits was evaluated. In summer, Actinobacteria and Bacteroidia increased, although this was not genus-specific. For fungi, Glomeraceae selectively increased in summer. In winter, Gram-negative bacterial genera, including those capable of nitrogen fixation and plant growth promotion, increased. Neutral model analysis revealed a strong stochastic influence on endophytic bacteria but a weak effect for fungi, especially in summer. The taxa with higher frequency than that predicted by neutral model shared environmental adaptability and symbiotic traits, whereas the frequency of pathogenic fungi was at or under the predicted value. These results suggest that community assembly of bacteria and fungi is regulated differently. The bacterial community was affected by stochastic and deterministic processes via bacterial response to drought (response trait), beneficial effect on plants (effect trait), and likely stable mutualistic interactions with plants suggested by the frequency of nodule bacteria. For fungi, mycorrhizal fungi were selected by plants in summer. The regulation of beneficial microbes by plants in both dry and wet seasons suggests the presence of plant-soil positive feedback in this natural desert ecosystem.
旱地生态系统经历季节性的严重干旱和适度降水周期。沙漠植物可能与根内生微生物建立共生关系，以在反复的干湿条件下生存。尽管在许多系统中已经发现了群落凝聚，但功能微生物的定殖及其与干旱地区季节性转变的关系还没有得到很好的理解。在这里，我们研究了根内生微生物类群及其与根定殖相关的特征，这些特征与美国西南部一个炎热沙漠地区的干湿季节有关。我们使用了 16S rRNA 的高通量 DNA 测序和五个沙漠灌木的内部转录间隔基因谱分析，并分析了内生微生物谱系在季节变化中的变化。评价了与微生物特征相关的中性群落模型拟合优度。在夏季，放线菌和拟杆菌增加，尽管这不是特定属的。对于真菌，Glomeraceae 在夏季选择性增加。在冬季，革兰氏阴性细菌属增加，包括固氮和促进植物生长的属。中性模型分析显示，内生细菌受随机影响很强，而真菌受随机影响较弱，尤其是在夏季。比中性模型预测频率更高的类群具有环境适应性和共生特征，而致病性真菌的频率在预测值或以下。这些结果表明，细菌和真菌的群落组装受到不同的调节。细菌群落受随机和确定性过程的影响，这些过程通过细菌对干旱的反应（反应特征）、对植物的有益影响（效应特征）以及与植物稳定的互利相互作用来调节，这由根瘤细菌的频率表明。对于真菌，夏季植物选择了菌根真菌。植物在干湿季节对有益微生物的调节表明，在这个自然沙漠生态系统中存在植物-土壤正反馈。
