Fungal footage fosters foresight into plant, animal disease

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Public release date: 22-Dec-2009

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Texas A & M AgriLife Communications

Fungal footage fosters foresight into plant, animal disease

http://www.eurekalert.org/pub_releases/2009-12/taac-fff121809.php

IMAGE: Dr. Shaw, Texas AgriLife Research plant pathologist, is pushing a

" revolutionary concept " on how fungi grow.

Mold and mildew may be doomed. Researchers are closer to understanding how these

and other fungi grow. " Fungi have a big impact on our dinner plate, " said Dr.

Shaw, Texas AgriLife Research plant pathologist. " We tend to think that

getting food on the table is easy. But fungi are major disease-causing organisms

for both plants and animals. With more research, we can find new ways to compete

with them. " Commonly known fungi are molds, mildews, mushrooms and yeast.

Anyone who thinks humans are not in an all-out war with pathogenic fungi need

only know this: Some 70 percent of the major disease-causing organisms are

fungi, according to Shaw.

That fact alone has researchers like Shaw going to great lengths to discover how

to combat the negative aspects of fungi.

Shaw, for one, is challenging existing scientific knowledge with new

observations on how fungal cells grow.

At a recent meeting of the International Fungal Biology Conference in Ensenada,

Mexico, Shaw demonstrated with unique movie footage his observation that fungi

cells grow and are shaped using both outward and inward flow of growth

materials.

" I'm pushing a revolutionary concept, " Shaw acknowledged.

Basically, fungi make a structure called a spore that helps the organism

disperse. Each spore has a cellular marker that tells the spore to germinate,

Shaw noted.

But researchers have puzzled over what makes the spore germinate and grow into

the structures characteristic of fungi. Often a fungus is a parasite, meaning

that it latches onto a plant or animal to live. Researchers want to find out how

to make the fungus stop growing without harming the animal skin or plant cells

on which the fungus grows.

A closer look shows that fungi are made of thread-like cells called hypha.

Magnified, the individual threads look like the outline of a blimp. Growth of

the fungi is confined to the apex or end of the hypha cell. That's different

from the way animal or plant cells grow, Shaw said.

A common thought for 50 years has been that the hypha direct their growth to the

apex of their cell through outward flow of growth material forming a longer and

longer blimp-like shape. This is called exocytosis. But Shaw found that there is

a region of the cell at the growing apex of the hypha that directs material

inward. That process is known as endocytosis. He discovered this with the help

of a student who took microscopic photos of the growing cell every 30 seconds

for six hours. That yielded a video that demonstrated growth. A movie from this

project can be seen at

http://www3.interscience.wiley.com/journal/119409055/suppinfo.

" We think the hypha is recycling material, " he said. " It is growing outward

toward a marker at the cell apex, but is also recycling that marker inward. We

call this the 'apical recycling model.' "

Shaw's work, supported by a National Science Foundation grant and the U.S.

Department of Agriculture, has been done on the common lab fungus Aspergillus

nidulans. It is not a pathogen, but information from Shaw's research translates

to disease-causing fungi and will help researchers learn how to stop their

harmful growth on plants and animals, he said.

Shaw said it is the balance between exocytosis and endocyotosis that results in

growth of fungus and the shape of the cell, and researchers who understand how

they grow can find better ways of stopping or curing fungal diseases.

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