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Dark septate endophytes isolated from a xerophyte plant promote the growth of Ammopiptanthus mongolicus under drought condition.

ABSTRACT: Dark septate endophytes (DSE) may facilitate plant growth and stress tolerance in stressful ecosystems. However, little is known about the response of plants to non-host DSE fungi isolated from other plants, especially under drought condition. This study aimed to seek and apply non-host DSE to evaluate their growth promoting effects in a desert species, Ammopiptanthus mongolicus, under drought condition. Nine DSE strains isolated from a super-xerophytic shrub, Gymnocarpos przewalskii, were identified and used as the non-host DSE. And DSE colonization rate (30-35%) and species composition in the roots of G. przewalskii were first reported. The inoculation results showed that all DSE strains were effective colonizers and formed a strain-dependent symbiosis with A. mongolicus. Specifically, one Darksidea strain, Knufia sp., and Leptosphaeria sp. increased the total biomass of A. mongolicus compared to non-inoculated plants. Two Paraconiothyrium strains, Phialophora sp., and Embellisia chlamydospora exhibited significantly positive effects on plant branch number, potassium and calcium content. Two Paraconiothyrium and Darksidea strains particularly decreased plant biomass or element content. As A. mongolicus plays important roles in fixing moving sand and delay desertification, the ability of certain DSE strains to promote desert plant growth indicates their potential use for vegetation recovery in arid environments.

SUBMITTER: Li X

PROVIDER: S-EPMC5962579 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Dark septate endophytes isolated from a xerophyte plant promote the growth of Ammopiptanthus mongolicus under drought condition.

Li Xia X He Xueli X Hou Lifeng L Ren Ying Y Wang Shaojie S Su Fang F

Scientific reports 20180521 1

Dark septate endophytes (DSE) may facilitate plant growth and stress tolerance in stressful ecosystems. However, little is known about the response of plants to non-host DSE fungi isolated from other plants, especially under drought condition. This study aimed to seek and apply non-host DSE to evaluate their growth promoting effects in a desert species, Ammopiptanthus mongolicus, under drought condition. Nine DSE strains isolated from a super-xerophytic shrub, Gymnocarpos przewalskii, were ident ...[more]

PMID: 29785041

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Project description:Although the ecological function of dark septate endophytes (DSEs) is well studied, little is known about the responses of the host plant to DSEs obtained from other plants, especially under conditions of heavy metal stress. This study aimed to investigate how DSEs from a heavy-metal habitat affect non-host plants in cadmium (Cd) stress soils, which then provides a basis for the application of DSEs in the cultivation of different plant and soil remediation strategies for polluted ecosystems. We isolated and identified two species of DSE (Acrocalymma vagum and Scytalidium lignicola) inhabiting the roots of Ilex chinensis (host plant) which are grown in metal-polluted habitats. Then, the Cd stress tolerance of the DSEs was tested using a pure culture of which the Cd concentration has been adjusted. Subsequently, we examined the performance of non-host plants (Medicago sativa and Ammopiptanthus mongolicus) which were inoculated with DSEs under Cd stress in a growth chamber. The results indicated that the two DSEs could grow under Cd stress in vitro, even when not exhibiting high levels of tolerance to Cd. The superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), soluble protein, and melanin of the DSE fungi reached maximal levels at concentrations of 30-60 mg Cd/L, indicating the important preventive strategies adopted by the DSE fungi in environments contaminated by Cd. Despite a decreased biomass of DSE hyphae with enhanced Cd concentrations, the accumulation of Cd in the DSE hyphae tended to show an increasing trend. Both DSEs were effective colonizers of the non-host plants. A. vagum and S. lignicola inoculation significantly promoted the biomass and the root architecture of the two non-host plants under Cd stress. A. vagum inoculation increased the total nitrogen (TN) of A. mongolicus, whereas inoculation with S. lignicola significantly increased the organic carbon (OC) of M. sativa. In particular, the DSE inoculation significantly improved the accumulation of Cd in plant tissues under Cd stress, demonstrating a potential application in the bio-remediation of heavy-metal-pollution areas. Our findings suggest that the DSE inoculation improved the root growth and nutrient absorption of non-host plants, altered the soil Cd concentration, and facilitated plant growth and survival under Cd stress. These results contribute to a better understanding of DSE-plant interactions in habitats contaminated by heavy metals.

Project description:BackgroundCBL1 is a calcium sensor that regulates drought, cold and salt signals in Arabidopsis. Overexpression of CBL1 gene in Arabidopsis and in Ammopiptanthus mongolicus showed different tolerant activities. We are interested in understanding the molecular mechanism of the upstream region of the CBL1 gene of A. mongolicus (AmCBL1). We investigated and characterized the promoter of the AmCBL1 gene, for promoters play a very important role in regulating gene expression in eukaryotes.ResultsA 1683-bp 5' flanking region was isolated from A. mongolicus. The sequence was identified as AmCBL1 promoter. Analysis of the promoter sequence indicated a 690-bp intron and some basic cis-acting elements were related to various environmental stresses and plant hormones. To identify the functional region of the AmCBL1 promoter, five plant expression vectors fused with the GUS (beta-glucuronidase) gene, driven by series deleted fragments of AmCBL1 promoter at different lengths from -1659, -1414, -1048, -296 to -167 bp relative to the transcriptional start site were constructed and transformed into Nicotiana tabacum L. cv. 89. Functional properties of each promoter segment were examined by GUS staining and fluorescence quantitative analyses using at least three single-copy PCR-positive plants of transgenic tobacco, treated with various environmental stresses and plant hormones for different times. We demonstrated that the AmCBL1 promoter was a vascular-specific and multiple-stress-inducible promoter. Our results further imply that the promoter fragment B1S3 possessed sufficient essential cis-acting elements, accounting for vascular-specific and stress-induced expression patterns. It may also indicate that for response to some stresses certain cis-elements are required in tissues outside the region of the B1S3 construct.ConclusionsTo help resolve uncertainties about the upstream regulatory mechanism of the CBL1 gene in desert plants, we suggest that the function of the AmCBL1 promoter, particularly under conditions of abiotic stress, to be examined for possible usefulness in molecular breeding. Regardless of the outcome, the allocation and relative quantification of the GUS-fusion AmCBL1 promoter segments at transcriptional levels in different tissues under various stresses across separate promoter segments suggests that the AmCBL1 promoter is a phloem-specific and multiple-stress-inducible promoter. These data coupled with the ongoing AmCBL1 5' UTR intron analyses provide a solid foundation for their future use in molecular breeding as new promoters of stress-resistance genes from desert plants.

Project description:This study mainly aimed to investigate the effects of dark septate endophytes (DSE) (Acrocalymma vagum, Paraboeremia putaminum, and Fusarium acuminatum) on the growth and microbial community composition in the rhizosphere soil of a medicinal plant, licorice (Glycyrrhiza uralensis), grown in the non-sterile soil under drought stress. The results showed that three DSE strains could effectively colonize the plant roots and form a strain-dependent symbiosis with licorice. Although drought stress declined the growth of licorice plants, these decreases were partly recovered by DSE inoculation. Specifically, the inoculation of A. vagum and P. putaminum significantly increased the biomass and glycyrrhizin content, whereas A. vagum and F. acuminatum increased glycyrrhizic acid content of host plants under drought stress. However, the inoculation of F. acuminatum showed significant negative effects on the shoot, root, and total biomass of licorice plants. In addition, the effects of DSE inoculation on the morphological, photosynthetic, and antioxidant parameters of licorice plants, and mineral nutrient and microbial community composition in the rhizosphere soil were dependent on the DSE species as well as water regime. Interestingly, DSE inoculation significantly increased AM fungi content under drought stress. In addition, DSE associated with water had a significant positive influence on soil organic matter, available phosphorus (P), AM fungi, leaf number, soluble protein, SOD activity, total root length, root branch, and glycyrrhizic acid content. Based on the results of variance partitioning analysis, 17.0, 34.0, 14.9, 40.1, 28.2, and 18.0% variations in shoot morphology, root morphology, plant biomass, active ingredient, photosynthetic parameters, and antioxidant parameters, respectively, were attributable to the presence of certain soil microorganisms. These findings suggest the possibility that DSE inoculation improved the root development and nutrient absorption of host plants, altered the soil microbiota, and might also contribute to plant growth and survival under drought conditions. As A. vagum exhibited positive effects on the plant biomass, morphological and physiological parameters, and active ingredient content in licorice plants under drought stress, it was considered to be the best fungus for licorice cultivation. These results contribute to the understanding of the ecological function of DSE fungi in dryland agriculture.

Project description:BACKGROUND: Fungi are asexually and sexually reproducing organisms that can combine the evolutionary advantages of the two reproductive modes. However, for many fungi the sexual cycle has never been observed in the field or in vitro and it remains unclear whether sexual reproduction is absent or cryptic. Nevertheless, there are indirect approaches to assess the occurrence of sex in a species, such as population studies, expression analysis of genes involved in mating processes and analysis of their selective constraints. The members of the Phialocephala fortinii s. l. - Acephala applanata species complex (PAC) are ascomycetes and the predominant dark septate endophytes that colonize woody plant roots. Despite their abundance in many ecosystems of the northern hemisphere, no sexual state has been identified to date and little is known about their reproductive biology, and how it shaped their evolutionary history and contributes to their ecological role in forest ecosystems. We therefore aimed at assessing the importance of sexual reproduction by indirect approaches that included molecular analyses of the mating type (MAT) genes involved in reproductive processes. RESULTS: The study included 19 PAC species and > 3, 000 strains that represented populations from different hosts, continents and ecosystems. Whereas A. applanata had a homothallic (self-fertile) MAT locus structure, all other species were structurally heterothallic (self-sterile). Compatible mating types were observed to co-occur more frequently than expected by chance. Moreover, in > 80% of the populations a 1:1 mating type ratio and gametic equilibrium were found. MAT genes were shown to evolve under strong purifying selection. CONCLUSIONS: The signature of sex was found in worldwide populations of PAC species and functionality of MAT genes is likely preserved by purifying selection. We hypothesize that cryptic sex regularely occurs in the PAC and that further field studies and in vitro crosses will lead to the discovery of the sexual state. Although structurally heterothallic species prevail, it cannot be excluded that homothallism represents the ancestral breeding system in the PAC.

Project description:Fungal endophytes can improve plant tolerance to abiotic stress conditions. Dark septate endophytes (DSEs) belong to phylogenetically non-related groups of root colonizing fungi among the Ascomycota with high melanin-producing activities. They can be isolated from roots of more than 600 plant species in diverse ecosystems. Still the knowledge about their interaction with host plants and their contribution to stress alleviation is limited. The current work aimed to test the abilities of three DSEs (Periconia macrospinosa, Cadophora sp., Leptodontidium sp.) to alleviate moderate and high salt stress in tomato plants. By including an albino mutant, the role of melanin for the interaction with plants and salt stress alleviation could also be tested. P. macrospinosa and Cadophora sp. improved shoot and root growth 6 weeks after inoculation under moderate and high salt stress conditions. No matter how much salt stress was applied, macroelement (P, N, and C) contents were unaffected by DSE inoculation. The four tested DSE strains successfully colonized the roots of tomato, but the colonization level was clearly reduced in the albino mutant of Leptodontidium sp. Any difference in the effects on plant growth between the Leptodontidium sp. wild type strain and the albino mutant could, however, not be observed. These results show that particular DSEs are able to increase salt tolerance as they promote plant growth specifically under stress condition. Increased plant biomasses combined with stable nutrient contents resulted in higher P uptake in shoots of inoculated plants at moderate and high salt conditions and higher N uptake in the absence of salt stress in all inoculated plants, in P. macrospinosa-inoculated plants at moderate salt condition and in all inoculated plants except the albino mutants at high salt condition. In summary, melanin in DSEs seems to be important for the colonization process, but does not influence growth, nutrient uptake or salt tolerance of plants.

Dataset Information

Dark septate endophytes isolated from a xerophyte plant promote the growth of Ammopiptanthus mongolicus under drought condition.

Publications

Dark septate endophytes isolated from a xerophyte plant promote the growth of Ammopiptanthus mongolicus under drought condition.

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