Seasonal Dynamics and Persistency of Endophyte Communities in Kalidium schrenkianum Shifts Under Radiation Stress

Diversity of Endophytes of Actinidia arguta in Different Seasons

The seasonal changes in environmental conditions can alter the growth states of host plants, thereby affecting the living environment of endophytes and forming different endophytic communities. This study employs Illumina MiSeq next-generation sequencing to analyze the 16SrRNA and ITS rDNA of endophytes in 24 samples of Actinidia arguta stem tissues across different seasons. The results revealed a high richness and diversity of endophytes in Actinidia arguta, with significant seasonal variations in microbial community richness. This study identified 897 genera across 36 phyla for bacteria and 251 genera across 8 phyla for fungi. Notably, 69 bacterial genera and 19 fungal genera significantly contributed to the differences in community structure across seasons. A distinctive feature of coexistence in the endophytic community, both specific and conservative across different seasons, was observed. The bacterial community in winter demonstrated significantly higher richness and diversity compared to the other seasons. Environmental factors likely influence the optimal timing for endophyte colonization. Solar radiation, temperature, precipitation, and relative humidity significantly impact the diversity of endophytic bacteria and fungi. In addition, seasonal variations show significant differences in the nutritional modes of fungal endophytes and the degradation, ligninolysis, and ureolysis functions of bacterial endophytes. This study elucidates the potential role of endophytes in assisting Actinidia arguta in adapting to seasonal changes and provides a theoretical basis for further exploration of functional microbial strains.

The root-associated Fusarium isolated based on fungal community analysis improves phytoremediation efficiency of Ricinus communis L. in multi metal-contaminated soils

Phytoremediation is a widely accepted bioremediation method of treating heavy metal contaminated soils. Nevertheless, the remediation efficiency in multi-metal contaminated soils is still unsatisfactory attributable to susceptibility to different metals. To isolate root-associated fungi for improving phytoremediation efficiency in multi-metal contaminated soils, the fungal flora in root endosphere, rhizoplane, rhizosphere of Ricinus communis L. in heavy metal contaminated soils and non-heavy metal contaminated soils were compared by ITS amplicon sequencing, and then the critical fungal strains were isolated and inoculated into host plants to improve phytoremediation efficiency in Cd, Pb, and Zn-contaminated soils. The fungal ITS amplicon sequencing analysis indicated that the fungal community in root endosphere was more susceptible to heavy metals than those in rhizoplane and rhizosphere soils and Fusarium dominated the endophytic fungal community of R. communis L. roots under heavy metal stress. Three endophytic strains (Fusarium sp. F2, Fusarium sp. F8, and Fusarium sp. F14) isolated from Ricinus communis L. roots showed high resistances to multi-metals and possessed growth-promoting characteristics. Biomass and metal extraction amount of R. communis L. with Fusarium sp. F2, Fusarium sp. F8, and Fusarium sp. F14 inoculation in Cd-, Pb- and Zn-contaminated soils were significantly higher than those without the inoculation. The results suggested that fungal community analysis-guided isolation could be employed to obtain desired root-associated fungi for enhancing phytoremediation of multi-metal contaminated soils.

Temporal variations in root-associated fungal communities of Potaninia mongolica, an endangered relict shrub species in the semi-arid desert of Northwest China

The semi-arid region of the Western Ordos plateau in Inner Mongolia, China, is home to a critically endangered shrub species, Potaninia mongolica, which originates from ancient Mediterranean regions. Root-associated microbiomes play important roles in plant nutrition, productivity, and resistance to environmental stress particularly in the harsh desert environment; however, the succession of root-associated fungi during the growth stages of P. mongolica is still unclear. This study aimed to examine root-associated fungal communities of this relict plant species across three seasons (spring, summer and autumn) using root sampling and Illumina Miseq sequencing of internal transcribed spacer 2 (ITS 2) region to target fungi. The analysis detected 698 fungal OTUs in association with P. mongolica roots, and the fungal richness increased significantly from spring to summer and autumn. Eurotiales, Hypocreales, Chaetothyriales, Pleosporales, Helotiales, Agaricales and Xylariales were the dominant fungal orders. Fungal community composition was significantly different between the three seasons, and the fungal taxa at various levels showed biased distribution and preferences. Stochastic processes predominantly drove community assembly of fungi in spring while deterministic processes acted more in the later seasons. The findings revealed the temporal dynamics of root-associated fungal communities of P. mongolica, which may enhance our understanding of biodiversity and changes along with seasonal alteration in the desert, and predict the response of fungal community to future global changes.

Metabarcoding and Metabolome Analyses Reveal Mechanisms of Leymus chinensis Growth Promotion by Fairy Ring of Leucocalocybe mongolica

Fairy rings are a unique ecological phenomenon caused by the growth of the fungal mycelium in the soil. Fairy rings formed by Leucocalocybe mongolica (LM) are generally distributed in the Mongolian Plateau, where they promote plant growth without fertilization and alleviate fertilizer use. We previously investigated the soil factors regulating growth promotion in a fairy ring ecosystem; however, the aspects of the plant (Leymus chinensis, LC) that promote growth have not been explored. Therefore, the present study investigated the endophyte diversity and metabolome of LC in an LM fairy ring ecosystem. We analyzed the leaf and root samples of LC from the DARK (FR) and OUT (CK) zones. The fairy rings significantly improved the fungal diversity of roots and leaves and the bacterial diversity of leaves in the FR zone. Ralstonia was the dominant bacteria detected in the LC leaves. In addition, Marasmius, another fairy ring fungal genus, was also detected with a high abundance in the roots of the FR zone. Furthermore, widely targeted metabolome analysis combined with KEGG annotation identified 1011 novel metabolites from the leaves and roots of LC and seven pathways significantly regulated by the fairy ring in the FR zone. The fairy ring ecosystem significantly downregulated the flavonoid metabolism in the leaves and roots of LC. The correlation analysis found Ralstonia is a potential regulatory factor of flavonoid biosynthesis in LC. In addition, salicylic acid and jasmonic acid were found upregulated in the leaves, probably related to Marasmius enrichment. Thus, the study details plant factors associated with enhanced growth in an LM fairy ring ecosystem. These findings lay a theoretical foundation for developing the fairy ring ecosystem in an agricultural system.

Characteristics and diversity of endophytic bacteria in Panax notoginseng under high temperature analysed using full-length 16S rRNA sequencing

Panax notoginseng is a traditional Chinese medicinal herb with diverse properties that is cultivated in a narrow ecological range because of its sensitivity to high temperatures. Endophytic bacteria play a prominent role in plant response to climate warming. However, the endophytic bacterial structures in P. notoginseng at high temperatures are yet unclear. In the present study, the diversity and composition of the endophytic bacterial community, and their relationships with two P. notoginseng plants with different heat tolerance capacities were compared using the full-length 16S rRNA PacBio sequencing system. The results revealed that the diversity and richness of endophytic bacteria were negatively associated with the heat tolerance of P. notoginseng. Beneficial Cyanobacteria, Rhodanobacter and Sphingomonas may be recruited positively by heat-tolerant plants, while higher amounts of adverse Proteobacteria such as Cellvibrio fibrivorans derived from soil destructed the cellular protective barriers of heat-sensitive plants and caused influx of pathogenic bacteria Stenotrophomonas maltophilia. Harmonious and conflicting bacterial community was observed in heat-tolerant and heat-sensitive P. notoginseng, respectively, based on the co-occurrence network. Using functional gene prediction of metabolism, endophytic bacteria have been proposed to be symbiotic with host plants; the bacteria improved primary metabolic pathways and secondary metabolite production of plants, incorporated beneficial endophytes, and combated adverse endophytes to prompt the adaptation of P. notoginseng to a warming environment. These findings provided a new perspective on the function of endophytes in P. notoginseng adaptation to high temperatures, and could pave the way for expanding the cultivable range of P. notoginseng.