Lasiodiplodia sp. ME4-2, an endophytic fungus from the floral parts of Viscum coloratum, produces indole-3-carboxylic acid and other aromatic metabolites.

BACKGROUND: Studies on endophytes, a relatively under-explored group of microorganisms, are currently popular amongst biologists and natural product researchers. A fungal strain (ME4-2) was isolated from flower samples of mistletoe (Viscum coloratum) during a screening program for endophytes. As limited information on floral endophytes is available, the aim of the present study is to characterise fungal endophytes using their secondary metabolites. RESULTS: ME4-2 grew well in both natural and basic synthetic media but produced no conidia. Sequence analysis of its internal transcribed spacer rDNA demonstrated that ME4-2 forms a distinct branch within the genus Lasiodiplodia and is closely related to L. pseudotheobromae. This floral endophyte was thus identified as Lasiodiplodia sp. based on its molecular biological characteristics. Five aromatic compounds, including cyclo-(Trp-Ala), indole-3-carboxylic acid (ICA), indole-3-carbaldehyde, mellein and 2-phenylethanol, were found in the culture. The structures of these compounds were determined using spectroscopic methods combined with gas chromatography. To the best of our knowledge, our work is the first to report isolation of these aromatic metabolites from a floral endophyte. Interestingly, ICA, a major secondary metabolite produced by ME4-2, seemed to be biosynthesized via an unusual pathway. Furthermore, our results indicate that the fungus ME4-2 is a potent producer of 2-phenylethanol, which is a common component of floral essential oils. CONCLUSIONS: This study introduces a fungal strain producing several important aromatic metabolites with pharmaceutical or food applications and suggests that endophytic fungi isolated from plant flowers are promising natural sources of aromatic compounds.

[Study function of endophytic fungus in parasitism process of mistletoe].

OBJECTIVE: To research the function of endophytes of mistletoe in parasitism process of mistletoe in Pterocarya stenoptera. METHOD: Endophytes from eight different parts of the mistletoe were separated by explant culture, and further screened by different CMC plates culture and DNS method to get cellulase high productive strains. The distribution of the endophytic fungus parasitized in mistletoe were prepared and stained to demonstrate by histological section of the intumescentia part of the P. stenoptera. RESULT: The histological section indicated that aboundent of hyphasma were distributed around the haustorium of the mistletoe. Eighty three strains of endophytic fungus were separated, 38 of them were able to degrade cellulose, 19 strains showed high cellulase activity and 10 of which were separated from the parasitic position. CONCLUSION: Endophytic fungus of mistletoe can secrete cellulase and assist the haustorium of mistletoe to breakthrough the cell walls as well as intercellular space tissues of the P. stenoptera, thus, the endophytic fungus plays an important role in the parasitism process of mistletoe in P. stenoptera.