摘要:植物内生菌具有帮助植物吸收营养元素，增强植物免疫力，抵御外界生物和非生物胁迫等功能。植物的根内和叶内存在大量的内生菌，影响着植物的健康生长。但不同植物地下（根内）和地上（叶内）内生原核微生物，以及与土壤微生物在组成和群落结构上的差异和联系还有待探索。以青藏高原高寒草甸三种优势植物青藏苔草（Carex moorcroftii）、火绒草（Leontopodium jacotianum）和高山嵩草（Carex parvula）为对象，研究了高寒草甸优势植物叶内、根内、土壤原核微生物组的组成及其与样品类型和植物类型之间的关系。结果表明：1）在门分类水平上，有13个门在土壤、叶内和根内之间有显著差异，只有5个门在不同植物之间有显著性差异，分别是变形菌门、厚壁菌门、酸杆菌门、疣微菌门以及FBP；2）在α多样性上，同种植物土壤、叶内、根内之间差异显著，而不同植物在土壤和根内差异显著，但在叶内无显著性差异；3）样品类型（叶内、根内以及土壤）是决定植物微生物组差异的最主要因子，对微生物群落变异的贡献度为20.13%；不同植物类型之间微生物群落也有显著性差异，植物类型对总变异的贡献率为14.41%，并且植物类型和植物相关部位（叶内，根内）以及土壤之间有强烈的交互作用（17.40%）。以上结果表明，每种植物叶内、根内以及周边土壤都具有独特的生态位，体现了原核微生物在样品类型和不同植物间上生态位的差异，同时也表明了原核微生物群落对这些生态位的适应性。最后，我们确定了与土壤相比有显著性差异的叶内和根内特有的微生物菌群并对高丰度菌群进行功能预测，以假单胞菌Pseudomonas为代表的菌群在叶内和根内显著富集，这些微生物包含参与多种代谢过程的功能基因，在促进营养元素吸收、提高植物在寒冷中的生态适应性方面有着重要的潜在功能。本研究的结果对深入探索高寒环境下植物-内生微生物互作机制提供了科学数据。



Abstract:The alpine meadow in the Qinghai-Tibet Plateau is the main natural pasture in China, and it is also an important ecosystem and alpine plant gene bank. The dominant meadow plants which show strong adaptions to the alpine climate are of great significance to grassland animal husbandry and maintenance of alpine ecosystem functions. Plant endophytes can promote plant growth because of their participations in nutrient cycling, hormone production as well as suppression of pathogens. Diverse and abundant endophytes harbored within leaf and root as symbioses with their hosts are critical to hosts' survival. Exploring community structure and diversity of prokaryotic communities, especially the endophytes of dominant plants in alpine meadows could provide new insights into the interactions between plants and their symbionts in the alpine environments. Bulk soil surrounding plants is a ‘seed pool’ of the microbes for plants, affecting the recruitment of the endophytes. However, the differentiations of prokaryotic communities among root endosphere, leaf endosphere and bulk soil in compositions and community structure need to be further explored. Here, we collected three dominant plants in alpine meadows including Carex moorcroftii, Leontopodium jacotianum and Carex vulpara, to study prokaryotic community compositions in leaf endosphere, root endosphere and bulk soil, and how sample types and plant types contributed to the variations of microbiomes using amplicon sequencing of 16S rRNA genes with Illumina HiSeq platform. The results showed that: 1) At phylum level, 13 phyla were significantly different among leaf endosphere, root endosphere and bulk soils (P<0.05), and only 5 phyla, namely Proteobacteria, Firmicutes, Acidobacteria, FBP and Verrucomicrobia, were statistically different among three studied plants (P<0.05). 2) For alpha diversity, there were significant differences among different sample types in all three plants (P<0.05), while significant differences of alpha diversity among different plants (P<0.05) were only observed in root endosphere and soil communities, and no significant differences were observed in leaf endosphere (P>0.05). 3) Sample type was the most important factor determining the structure of prokaryotic community, contributing 20.13% to the variation of prokaryotic community structure. The prokaryotic community structure among different plants also had significantly differences, and plant types contributed 14.41% to the total variation. The strong interactions between plant types and sample types were also observed (17.40%). The results indicated that leaf endosphere, root endosphere and bulk soil created unique niches for prokaryotic communities, showing microbial niche differentiations with sample types and plant species and reflecting certain adaptability of prokaryotic communities to these niches. Finally, we identified the specific microbes in leaf endosphere and root endosphere which were significantly different from those in soils. Pseudomonas, as a typical representative, was significantly enriched in both leaf endosphere and root endosphere. These microbes contained functional genes involved in various metabolic processes and had important potential functions in promoting nutrient uptake and improving plant ecological adaptability in cold environment. This study revealed key factors driving the differentiations of prokaryotic communities in dominant alpine meadow plants, and the plant-endophyte interactions in different plant compartments.





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