Variability in Indian isolates of Arthrobotrys dactyloides Drechsler: a nematode-trapping fungus

Analysis of Nuclear Dynamics in Nematode-Trapping Fungi Based on Fluorescent Protein Labeling

Nematophagous fungi constitute a category of fungi that exhibit parasitic behavior by capturing, colonizing, and poisoning nematodes, which are critical factors in controlling nematode populations in nature, and provide important research materials for biological control. Arthrobotrys oligospora serves as a model strain among nematophagous fungi, which begins its life as conidia, and then its hyphae produce traps to capture nematodes, completing its lifestyle switch from saprophytic to parasitic. There have been many descriptions of the morphological characteristics of A. oligospora lifestyle changes, but there have been no reports on the nuclear dynamics in this species. In this work, we constructed A. oligospora strains labeled with histone H2B-EGFP and observed the nuclear dynamics from conidia germination and hyphal extension to trap formation. We conducted real-time imaging observations on live cells of germinating and extending hyphae and found that the nucleus was located near the tip. It is interesting that the migration rate of this type of cell nucleus is very fast, and we speculate that this may be related to the morphological changes involved in the transformation to a predatory lifestyle. We suggest that alterations in nuclear shape and fixation imply the immediate disruption of the interaction with cytoskeletal mechanisms during nuclear migration. In conclusion, these findings suggest that the signal initiating nuclear migration into fungal traps is generated at the onset of nucleus entry into a trap cell. Our work provides a reference for analysis of the dynamics of nucleus distribution and a means to visualize protein localization and interactions in A. oligospora.

Variabilities of two Drechslerella dactyloides isolates in Korea and high predacity against Bursaphelenchus xylophilus

Drechslerella dactyloides generates elongate ellipsoid conidia and three-celled rings. Recently, Drechslerella dactyloides CNU 091025 and CNU 091026 were isolated in Korea, which generated elongate ellipsoid, Y-shaped and reaphook-shaped conidia, three-celled rings and fishhook-shaped traps. Therefore, molecular phylogenetic analysis, morphological variability, and nematode capturing ability were tested in this study. CNU 091025 generated two-celled or three-celled Y-shaped conidia, reaphook-shaped conidia, and elongate ellipsoid conidia, 17.2, 40.9, and 41.9%, respectively. Some fishhook-shaped rings connecting together formed two-dimensional web. Both fungi showed high trap-forming and nematode-capturing ability; especially CNU 091026 captured 100% Bursaphelenchus xylophilus within 24 h after inoculation.