Nuclear dynamics in the homothallic ascomycete Sordaria fimicola

Kulsumpun Krobanan,Wei-Chiang Shen

doi:10.1186/s40529-018-0233-y

Abstract

BackgroundThe coprophilous ascomycete Sordaria fimicola usually reproduces sexually. Sexual differentiation in S. fimicola is accompanied by cellular and morphological changes, followed by multicellular tissue development to complete the sexual cycle. Although the morphological features of the sexual reproductive structure in S. fimicola have been well characterized, little is known about the nuclear dynamics and organization during these processes. Therefore, in this study, we successfully developed an Agrobacterium-mediated protoplast transformation protocol and generated histone H2B-mCherry-labeled S. fimicola strains. The life cycle of S. fimicola begins with germination of the ascospore and ends with the formation and discharge of new ascospores from the mature black sexual fruiting bodies, the so-called perithecia. The nuclear dynamics of the fluorescently labeled strains were examined during ascospore germination, hyphal elongation, and hyphal fusion using fluorescent microscopy.ResultsLive imaging revealed that the nuclei in the germlings and fusion hyphae during the pre-contact interaction are located adjacent to the tip.ConclusionsThis is the first report of the application of a fluorescence labeling technique in S. fimicola. This application will help researchers gain a better understanding of nuclear distribution and investigate the protein–protein interaction networks during fruiting body formation for advanced molecular genetic studies in S. fimicola.

Highlights

The coprophilous ascomycete Sordaria fimicola usually reproduces sexually
The S. fimicola life cycle starts with mature sexual spores released from fruiting bodies embedded in animal dung, and spore germination is known to be induced by certain stimulants including sodium acetate (Bretzloff 1951)
To expand the capabilities of S. fimicola in genetic analyses, in this study, we conducted the first successful transformation of S. fimicola and generated a histone H2B-mCherry-labeled strain, which was used to examine the nuclear dynamics during ascospore germination, sexual differentiation, and hyphal extension

Summary

Introduction

The coprophilous ascomycete Sordaria fimicola usually reproduces sexually. Sexual differentiation in S. fimicola is accompanied by cellular and morphological changes, followed by multicellular tissue development to complete the sexual cycle. Sordaria fimicola is a well-known homothallic ascomycete commonly found in fecal matter and has long been used to study genetic recombination, chromosome segregation, and the fungal life cycle as a whole (Ingold and Dring 1957; Olive 1956). S. fimicola has long been used for various aspects of fungal research (Ingold and Dring 1957; Ingold and Hadland 1959; Kitani and Whitehou 1974; Olive 1956), no strain generated via a genetic transformation method has yet been established for this organism to date. To expand the capabilities of S. fimicola in genetic analyses, in this study, we conducted the first successful transformation of S. fimicola and generated a histone H2B-mCherry-labeled strain, which was used to examine the nuclear dynamics during ascospore germination, sexual differentiation, and hyphal extension. In addition to providing a useful tool for genetic research, our time-lapse video of the nuclear dynamics should facilitate a better understanding of the detailed nuclear behaviors that occur during the life cycle and reproductive events in S. fimicola

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