Highlighting four posters from the 2022 Fungal Genetics Conference

We take a closer look at some of the posters presented at this year’s Fungal Genetics Conference chosen by PhD students.

The 2022 Fungal Genetics Conference was held earlier this year, and two PhD students from Vera Meyer’s lab, one of the co-Editors-in-Chief of Fungal Biology and Biotechnology, attended and selected their top 4 posters from the conference. We present a brief overview of these researchers and their research.

 

Claudia Petrucco

I am a third year PhD student in the program of molecular genetics and microbiology at Duke University School of Medicine (Durham, North Carolina). I am in Daniel Lew’s lab.

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

Aureobasidium pullulans is a black yeast-like fungus with an unconventional lifestyle. Most well-studied budding yeast 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 yeast, A. pullulans mother cells can be multi-nucleate and produce multiple buds within a single division cycle. Our initial 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 in regards to nuclear segregation, polarity establishment, and possibly other phenomena.

To investigate this interesting cell biology, I have begun developing a molecular genetics toolbox. This includes an efficient transformation system, fluorescent probes for intracellular structures of interest, and live-cell imaging. It is our intention to transform A. pullulans into a tractable system for basic cell biology research. My initial findings, using these tools, suggest that A. pullulans undergoes a form of “semi-open” mitosis where the nuclear envelope remains intact but the nuclear pore complexes disassemble. In the future, I will examine nuclear segregation in A. pullulans to understand how mother cells ensure each bud receives a single nucleus during division.

 

Louis Chevalier

PhD Student: Institut Jacques Monod, CNRS/Univ Paris Diderot, Paris

Tip growth is a highly polarized cellular process used by walled cells of fungi, plants, or bacteria to colonize space, reproduce or infect. Tip growing cells are encased in a rigid cell wall that ensures surface integrity and limits cell growth, yet these cells can elongate at unusual high speeds of up to few mm/hrs. These considerations raise the fundamental question of how the cell wall may be dynamically assembled at cell tips to safeguard integrity while allowing rapid surface shape changes.

We implemented a sub-resolution imaging approach to map cell wall thickness spatio-temporal dynamics, cell wall elasticity, and turgor pressure in very rapid growing hyphal cells of the filamentous fungus Aspergillus nidulans. We found that hyphal cells grow with a near homogenous cell wall thickness of about 80nm, and a marked gradient in cell wall bulk elastic modulus, with hyphal tips being twice softer than cell sides. By co-imaging cell wall thickness dynamics and secretory vesicle accumulations that deliver new cell wall material to cell tips, we found that both fluctuated with typical amplitudes of up to 150% and periods of 1-2 min during growth. Affecting secretory vesicle transport or fusion caused a rapid loss of polarity, growth arrest, and rapid thickening of the cell wall at cell tips.

These data provide unprecedented details 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 biocontrol potential of Trichoderma against Armillaria 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.

Armillaria, a mushroom-producing fungus, grows underground where it searches for host plants to attack and feed on. There, it parasitises trees and shrubs, often causing their decline and death. Mycelium can survive for decades while searching for food and have the ability to span huge areas, even making one individual of Armillaria the largest organism in the world.

Armillaria root rot (ARR), the disease caused by species of Armillaria, impacts gardens, forestry, vineyards, stone fruit and nut production. Despite its wide-reaching effects, there is currently no chemical control available. My PhD research investigates the potential to use another fungus, Trichoderma, as a biocontrol agent against Armillaria. Trichoderma can live within the roots of plants without causing harm to its host, as well as attack other fungi including Armillaria.

My research studies the protective ability of various Trichoderma isolates to prevent or lessen disease from ARR. In planta studies in strawberry and privet plants have shown two Trichoderma atrobrunneum isolates to have strong potential in protecting against ARR. However, it is not yet known how Trichoderma is able to control disease. To investigate methods of control, I study the production of enzymes and volatile organic compounds by Trichoderma, as well as how Trichoderma alters the pH of its environment. The Trichoderma atrobrunneum isolate with the best biocontrol potential has been sequenced, and future work will investigate genes potentially important in antagonism against Armillaria.

 

Tejas A. Navaratna

Postdoctoral scholar, 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 efficiently break down plant matter, releasing sugars and other carbohydrates that they and their host mammal consume for energy.

To better understand the biology of anaerobic fungi and engineer them for use in biotechnology, such as for the production of useful enzymes and waste conversion, we are applying gene editing techniques. Specifically, we are using CRISPR-based and gene insertion methods to knock out several proteins thought to be involved in metabolism to demonstrate higher production of fatty acids. We are also adding fluorescent labels to visualize fungal cellular processes such as spore production and plant matter invasion. To achieve these aims, we have characterized DNA delivery to the immature, single-cell life stage of anaerobic fungi, the zoospore, by flow cytometry, and also found that we can successfully confer antibiotic resistance to anaerobic fungi. Applying these tools is an important step towards developing custom microbes for industrial and academic use.

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