Gargouri Mahmoud, Karray Fatma, Chebaane Asma, Mhiri Najla, Partida-Martínez Laila Pamela, Sayadi Sami, Mliki Ahmed
Laboratory of Plant Molecular Physiology, Centre of Biotechnology of Borj-Cedria, PB.901, 2050 Hammam-Lif, Tunisia.
Laboratory of Environmental Bioprocesses, Centre of Biotechnology of Sfax, BP 1177, 3018 Sfax, Tunisia.
Sci Total Environ. 2021 Jun 15;773:145008. doi: 10.1016/j.scitotenv.2021.145008. Epub 2021 Feb 8.
The effects of aridity on soil and water-use efficient (WUE) crop species are relatively well known. However, the understanding of its impacts on the dynamics of below-ground microorganisms associated with plant roots is less well understood.
To investigate the influence of increasing aridity on the dynamics of the fungal communities, samples from the root endosphere and rhizosphere associated with the prickly pear cactus trees (Opuntia ficus-indica) growing along the aridity gradient were collected and the internal transcribed spacer (ITS) were sequenced. The diversity and network analyses of fungal taxa were determined along with standard measurements of soil parameters.
We found that (i) the fungal community exhibited similar alpha diversity and shared a set of core taxa within the rhizosphere and endosphere, but there was significant beta diversity differences; (ii) the relative abundance of major phyla was higher in the rhizosphere than in the endosphere; (iii) arbuscular endomycorrhizal colonization was highest in the humid climate and decreased under lower-arid, and was negatively correlated with increased concentration of Ca in the soil; (iv) increased aridity correlated with increased connectivity of the soil microbial-root fungal networks in the arid soils, producing a highly cohesive network in the upper-arid area; and (v) distinct fungal hubs sculpt the fungal microbiome network structure in the rhizosphere and endosphere within each bioclimatic zone.
Our findings highlight the importance of gradient analysis-based correlation network as a powerful approach to understand changes in the diversity, the dynamics, and the structure of fungal communities associated with the rhizosphere-endosphere interaction and led to the identification of microbes at each bioclimatic zone that are potentially involved in promoting the survival, protection, and growth of Opuntia trees. The variability of fungal hubs composition depending on plant compartment and bioclimatic zone will give key implications for the application of rhizospheric fungi and endophytes as microbial inoculants in agriculture, as well as in the conservation and restoration of cacti plants in arid and semi-arid lands against the backdrop of climate change. Overall, this study will enhance our understanding of the microbiomes'dynamic of CAM plants in nature.
干旱对土壤及水分利用效率高的作物物种的影响相对广为人知。然而，对于其对与植物根系相关的地下微生物动态的影响，人们了解较少。
为研究干旱加剧对真菌群落动态的影响，采集了沿干旱梯度生长的仙人掌树（仙人掌属）根内圈和根际的样本，并对其内部转录间隔区（ITS）进行测序。同时测定了真菌分类群的多样性和网络分析以及土壤参数的标准测量值。
我们发现：（i）真菌群落在根际和根内圈表现出相似的α多样性，并共享一组核心分类群，但存在显著的β多样性差异；（ii）主要门类在根际的相对丰度高于根内圈；（iii）丛枝内生菌根定殖在湿润气候下最高，在较低干旱条件下降低，且与土壤中钙浓度的增加呈负相关；（iv）干旱加剧与干旱土壤中土壤微生物 - 根真菌网络的连通性增加相关，在上部干旱地区形成了高度凝聚的网络；（v）不同的真菌枢纽塑造了每个生物气候区内根际和根内圈的真菌微生物组网络结构。
我们的研究结果强调了基于梯度分析的相关网络作为一种强大方法的重要性，有助于理解与根际 - 根内圈相互作用相关的真菌群落的多样性、动态和结构变化，并识别出每个生物气候区中可能参与促进仙人掌树生存、保护和生长的微生物。真菌枢纽组成因植物区室和生物气候区而异，这将对根际真菌和内生菌作为农业微生物接种剂的应用，以及在气候变化背景下干旱和半干旱地区仙人掌植物的保护和恢复具有关键意义。总体而言，本研究将增进我们对自然界中景天酸代谢植物微生物组动态的理解。
