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Highlighting four posters from the 2022 Fungal Genetics Conference

The 2022 Fungal Genetics Conference was held earlier this year, and two PhD students from the lab of Vera Meyer, one of the co-editors of fungal biology and biotechnology, attended and selected their top 4 conference posters. We present a brief overview of these researchers and their research.

Claudia Petrucco

I am a third-year doctoral candidate in the Molecular Genetics and Microbiology program at Duke University School of Medicine (Durham, NC). I’m in Daniel Lew’s lab.

Probing the unconventional lifestyle of multi-budding yeast, Aureobasidium pullulans

Aureobasidium pullulans is a black yeast-like fungus with an unconventional lifestyle. Most well-studied budding yeasts undergo a life cycle where a mother cell produces a single bud, distributes important cellular components between mother and bud, and then divides forming two cells each with a single nucleus. Unlike these yeasts, A. pullulans the mother cells can be multinucleated and produce several buds during the same cycle of division. Our first observations suggest that almost all buds inherit exactly one nucleus regardless of the number of nuclei or buds in the mother. These findings suggest that A. pullulans may exhibit novel cell biology with respect to nuclear segregation, polarity establishment, and possibly other phenomena.

To study this interesting cell biology, I started developing a molecular genetics toolkit. This includes an efficient transformation system, fluorescent probes for intracellular structures of interest, and live cell imaging. Our intention is to transform A. pullulans in a manageable system for basic cell biology research. My first results, using these tools, suggest that A. pullulans undergoes a “half-open” form of mitosis where the nuclear envelope remains intact but the nuclear pore complexes disassemble. In the future, I will examine nuclear segregation in A. pullulans understand how parent cells ensure that each bud receives a single nucleus during division.

Louis Chevalier

PhD student: Jacques Monod Institute, CNRS/Univ Paris Diderot, Paris

Spike growth is a highly polarized cellular process used by walled cells of fungi, plants, or bacteria to colonize space, reproduce, or infect. Spike-growing cells are enclosed in a rigid cell wall that provides surface integrity and limits cell growth, but these cells can elongate at unusually high rates of up to a few mm/hr. These considerations raise the fundamental question of how the cell wall can be dynamically assembled at cell ends to preserve integrity while allowing for rapid changes in surface shape.

We implemented a sub-resolution imaging approach to map the spatiotemporal dynamics of cell wall thickness, cell wall elasticity, and turgor pressure in very rapidly growing hyphal cells of the filamentous fungus. Aspergillus nidulans. We found that hyphal cells grow with an almost homogeneous cell wall thickness of approximately 80 nm and a marked gradient in the bulk elastic modulus of the cell wall, with the tips of the hyphae being twice as smooth as the sides of the cells. . By co-imagining the dynamics of cell wall thickness and accumulations of secretory vesicles that supply new cell wall material to cell tips, we found that both fluctuate with typical amplitudes of up to 150%. and periods of 1-2 min during growth. Affecting transport or fusion of secretory vesicles caused rapid loss of polarity, growth arrest, and rapid thickening of the cell wall at cell ends.

These data provide unprecedented detail on cell wall dynamics from synthesis to assembly and deformation, and suggest important dynamic coupling mechanisms between surface material synthesis and deformation rates, likely essential to support rapid growth and cell viability.

Morgan Millen

Fighting fungi with fungi: the biological control potential of Trichoderma versus armillary root rot

Millen M1,2, Drakulic J2, Cromey M2, Bailey AM1, Foster GD1

Author affiliations: 1School of Biological Sciences, University of Bristol, BS8 1TQ, UK; 2 Royal Horticultural Society, RHS Garden Wisley, Woking, GU23 6QB, UK.

armillary, a mushroom-producing fungus, grows underground where it seeks host plants to attack and feed on. There it parasitizes trees and shrubs, often causing them to wither and die. The mycelium can survive for decades while foraging and has the ability to cover large areas, making even an individual armillary the largest organism in the world.

armillary root rot (ARR), the disease caused by species of armillary, has an impact on gardens, forestry, vineyards, stone fruit and nut production. Despite its widespread effects, there are currently no chemical controls available. My doctoral research is studying the possibility of using another fungus, Trichodermaas a biological control agent against armillary. Trichoderma can live in plant roots without harming its host, as well as attack other fungi, including armillary.

My research studies the protective capacity of various Trichoderma isolates to prevent or mitigate ARR disease. In planta studies on strawberries and privet have shown two Trichoderma atrobruneum isolates with high protective potential against ARR. However, it is not yet known how Trichoderma is able to control the disease. To study control methods, I study the production of enzymes and volatile organic compounds by Trichodermaas well as how Trichoderma changes the pH of its environment. the Trichoderma atrobruneum isolate with the best biocontrol potential has been sequenced, and future work will investigate genes potentially important in antagonism against armillary.

Tejas A. Navaratna

Postdoctoral Fellow, Department of Chemical Engineering

University of California, Santa Barbara, USA

Anaerobic fungi are fascinating organisms found in the stomachs of large herbivores. They have the powerful ability to break down plant matter efficiently, releasing sugars and other carbohydrates which they and their mammalian host consume for energy.

To better understand the biology of anaerobic fungi and design them for use in biotechnology, such as for the production of useful enzymes and the conversion of waste products, we apply gene editing techniques. Specifically, we use CRISPR-based and gene insertion methods to knock out several proteins thought to be involved in metabolism to demonstrate higher fatty acid production. We also add fluorescent markers to visualize fungal cellular processes such as spore production and invasion of plant material. To achieve these goals, we characterized DNA delivery to the immature, unicellular life stage of anaerobic fungi, the zoospore, by flow cytometry, and also found that we can successfully confer antibiotic resistance to anaerobic fungi. The application of these tools is an important step towards the development of personalized microbes for industrial and academic use.