Abstract
Dark septate endophytes (DSEs) are often trace element (TE)-tolerant fungi and are abundant in TE-polluted environments. The production of melanin, a black polymer found in cell walls, was hypothesized by several authors to play a role in the TE tolerance of DSEs. To test this hypothesis, we established a series of experiments using albino strains and melanin inhibitors and examined the responses to Cd and Zn. Six DSEs belonging to genera Cadophora sp., Leptodontidium sp. and Phialophora mustea, were evaluated. The strains mainly produced 1,8-dihydroxynaphthalene (DHN) melanin whereas 3,4-dihydroxyphenylalanin melanin was also synthetized. Cd and Zn decreased melanin synthesis in most of the strains. A reduction in melanin concentration in hyphae through the use of tricyclazole, an inhibitor of DHN-melanin synthesis, did not reduce the tolerance of the strains to Cd and Zn. Similarly, albino mutants of Leptodontidium sp. were not more sensitive to Cd and Zn than the WT strain. Moreover, tricyclazole-treated colonies accumulated less Cd but more Zn compared to untreated colonies. The Cd and Zn contents of Leptodontidium albino strains were variable and similar to that of the WT. The results suggest that melanin production is not an important functional trait that contributes to Cd and Zn tolerance, but might contribute to Cd accumulation.
Highlights
Dark septate endophytes (DSEs) are polyphyletic, sterile or conidial, ascomycetes characterized by darkly pigmented mycelia and septate hyphae [1]
There was no reciprocal best hit for all the 26 proteins listed identified in E. dermatitidis based on the transcriptomic analyses of Fonsecaea monophora in the two DSE genomes and the blast results showed the same pattern, except in one laccase gene, where Leptodontidium sp. had homologous protein and Cadophora sp. did not (Table S2)
We have shown that the three DSE Leptodontidium sp., Cadophora sp. and P. mustea mainly produced 1,8-dihydroxynaphthalene (DHN) melanin and Cadophora sp. and P. mustea could produce DOPA-melanin
Summary
Dark septate endophytes (DSEs) are polyphyletic, sterile or conidial, ascomycetes characterized by darkly pigmented mycelia and septate hyphae [1] They have been observed in the roots of more than 600 plant species spanning 100 plant families [2]. Regarding metal-contaminated soils, DSE colonization was reported in plant roots of Pb and/or Zn mining or smelting sites and Ni/Cu smelter areas [3,6,7]. In these environments, the relative abundance of DSEs increased with TE stress compared to other root-associated fungi [3,6]. Several authors hypothesized that the high melanin-derived pigmentation could partially explain the relatively high TE tolerance of DSEs and their TE accumulation capacities in the mycelia of DSEs [19,20]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
