Two new root endophyte and nematode cyst parasite species of the widely distributed genus Laburnicola

Abstract

Fungal root endophytes, including the common form group of dark septate endophytes (DSEs), represent different taxonomic groups with potentially diverse life strategies. During surveys of DSE communities and of nematode cysts colonizing fungi, isolates representing Laburnicola (Didymosphaeriaceae, Pleosporales) lineages were discovered. Here we carried out a comprehensive study of the phylogenetic relationships and taxonomy of fungi collected from plant roots in Hungary, Mongolia, and Kazakhstan and from eggs of the cereal cyst nematode Heterodera filipjevi in Turkey. In addition to the study of the morphology and culture characteristics of the strains, four loci (internal transcribed spacer, partial large and small subunit regions of nuclear ribosomal DNA and partial translation elongation factor 1-alpha) were used to infer the molecular phylogenetic relationships of the strains within Laburnicola. The isolates were found to represent two distinct lineages, which are described here as novel species, Laburnicola nematophila and L. radiciphila. The interaction of the strains with plants and nematodes was examined using in vitro bioassays, which revealed endophytic interactions with the plant roots and parasitic interactions with the nematode eggs. Analyses of similar ITS sequences found in public databases revealed that members of the genus Laburnicola are widely distributed characteristic members of the plant microbiome, and they are reported as parasites of plant parasitic cyst nematodes here for the first time.

Polydomus karssenii gen. nov. sp. nov. is a dark septate endophyte with a bifunctional lifestyle parasitising eggs of plant parasitic cyst nematodes (Heterodera spp.)

“…The fungal infection of nematode eggs observed in this study resembled the infection process in the previously studied DSEs P. sieberi (Ashrafi et al 2018) and a recently described Laburnicola species, L. nematophila (Knapp et al 2022). Despite formation of appressoria-like structures during plant colonisation, these infection structures were not observed when the fungus colonised the nematode eggs.…”

Laburnicotides A–F: Acyclic N-Acetyl Oligopeptides from the Nematode-Cyst-Associated Fungus Laburnicola nematophila

“…The HR-ESI-MS spectrum revealed a protonated molecular ion peak at m/z 578.2971 [M + H] + (calculated 578.2973) and a sodium adduct at m/z 600.2790 [M + Na] + (calculated 600.2793) determining the molecular formula of 2 as C 31 H 39 N 5 O 6 indicating 15 degrees of unsaturation equal to those of 1, despite having a lesser molecular formula by the C 3 H 6 moiety reflecting the difference of 42 Da in their molecular masses. The 1 H and 13 C NMR spectral data of 2 (Table 1) revealed features similar to those in 1 suggesting its common nature of being an acylic N-acetyl oligopeptide. A careful interpretation of 1 H NMR, 1 H− 1 H COSY, and ROESY spectral data of 2 (Table 1 and Figures 1 and 2) in methanol-d 4 and DMSO-d 6 suggested the presence of four amino acid residues, namely, Trp, Phe, and Leu as in 1 while the fourth was identified as an alanine (Ala) residue by revealing a characteristic spin system extending from an α-proton signal at δ H 4.29 (q, J = 7.2 Hz, H-2″) to a doublet methyl group at δ H 1.17 (d, J = 7.2 Hz, H 3 -3″).…”

“…a Measured in DMSO-d 6 at 175 MHz for13 C and 700 MHz for 1 H. b Measured in methanol-d 4 at 175 MHz for13 C and 700 MHz for 1 H. disubstituted aromatic ring through a spin system starting at δ H 7.58 (d, J = 7.9 Hz) extending to δ H 6.95 (td, J = 7.8, 1.8 Hz), δ H 7.03 (ddd, J = 8.0, 7.8, 1.2 Hz), and δ H 7.31 (d, J = 8.0 Hz) in addition to a key correlation between a deshielded NH signal at δ H 11.05 and an olefinic proton at δ H 7.04 (d, J = 2.0 Hz) suggesting the presence of an indole group indicating a tryptophan (Trp) residue. The 1 H− 1 H COSY spectrum of 1 (Figure…”

“…a Measured in DMSO-d 6 at 175 MHz for13 C and 700 MHz for 1 H.ACS Omegahttp://pubs.acs.org/journal/acsodf Article https://doi.org/10.1021/acsomega.4c02719 ACS Omega XXXX, XXX, XXX−XXX indicating its presence as a N-acetyl terminus connected to the Trp residue. In addition, the HMBC spectrum of 2 (Figure 1) disclosed key correlations from H-2′ (δ H 4.33, dd, J = 9.5, 5.5 Hz, αH-Leu) to C-1 and C-1′ (δ C 174.2).…”

“…1 H and13 C NMR Data of 5 and 6Measured in DMSO-d 6 at 175 MHz for13 C and 700 MHz for 1 H. b Measured in methanol-d 4 at 175 MHz for13 C and 700 MHz for 1 H.…”