The Zoige pioneer plant Leymus secalinus has different endophytic bacterial community structures to adapt to environmental conditions

Abstract

Background: Leymus secalinus is a pioneer plant grown in the Zoige desertified alpine grassland and it is also one of the dominant plant species used for environmental remediation. L. secalinus plays a large role in vegetation reconstruction in sandy land, but the abundance and diversity of its endophytes have not yet been investigated.

Objectives: This study was performed to investigate the changes in the endophytic bacterial community structure of L. secalinus under different ecological environments and to analyze the effects of environmental changes and different plant tissues on the L. secalinus endophytic bacteria.

Methods: Leaf, stem, and root tissue samples of L. secalinus were collected from Zoige Glassland (Alpine sandy land) and an open field nursery (Control). DNA was extracted and the 16S ribosomal DNA was amplified. The sequence library was sequenced on an Illumina MiSeq platform and clustered by operational taxonomic units (OTUs). α-diversity and β-diversity analyses, species diversity analyses, functional prediction, and redundancy (RDA) analyses for the soil physicochemical properties were conducted.

Results: α-diversity and β-diversity analyses showed that the endophytic bacteria in L. secalinus varied in different areas and tissues. The abundance of Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, which is related to nitrogen fixation, increased significantly in the L. secalinus found in the Zoige Grassland.Moreover, the abundance of nutrition metabolism and anti-stress abilities increased in functional prediction in the desert samples. The soil physicochemical properties had an insignificant influence on bacterial diversity.

Conclusion: The changes in the endophytic bacterial community structure in L. secalinus were significant and were caused by environmental alterations and plant choice. The endophytic bacteria in L. secalinus grown in alpine sandy land may have greater anti-stress properties and the ability to fix nitrogen, which has potential value in environmental remediation and agricultural production.

Keywords: 16S rRNA gene sequencing; Endophytic bacterium; Leymus secalinus; Nitrogen fixation; Vegetation remediation; Zoige alpine grassland.

Figure 1. Sampling location and organism.

Figure 2. β-diversity data.

(A) Scatter plot of PCoA based on UniFrac and Bray-Curtis. (B) Scatter plot of the PCA score based on the Euclidean distance. (C) Hierarchical clustering. PCA, principal component analysis; PCoA, principal coordinates analysis.

Figure 3. Relative abundance of endophytic bacteria.

Endophytic bacteria communities associated with Leymus secalinus at the phylum level (A) and genus level (B) and LEfSe analysis between DL and L groups (C). LEfSe, linear discriminant analysis (LDA) effect size.

Figure 4. Abundance heatmap of the KEGG function of endophytic communities.

KEGG, Kyoto Encyclopedia of Genes and Genomes.

Figure 5. RDA analysis at phylum level (A) and genus level (B).

RDA, redundancy analysis.