Gene 'talk' triggers fungus defense.

Plants can't speak, but they do communicate. When a spore from a disease-causing fungus lands on an alfalfa leaf, an intricate chemical conversation takes place that determines whether the plant becomes infected. Interpreting this complex interplay of signals could be a key to unlocking novel ways to develop disease-resistant plants, suggests plant pathologist Marty Dickman, University of Nebraska-Lincoln.

Developing alfalfa plants resistant to anthracnose, a disease caused by a fungus, is one focus of Dickman's research. His broader interest is how fungi cause plant diseases and how plants defend themselves against fungi. "It's amazing how little we know about disease," he points out.

What Dickman does know about alfalfa anthracnose is that when a spore from the disease-causing fungus Colletotricum trifolii lands on an alfalfa leaf, it grows a long tube that develops a cushion-like structure at its tip that penetrates the leaf. Once inside the leaf, the fungus generates branching structures, called hyphae, that spread through the plant cells, causing disease.

In some plants, hyphae never spread after penetrating the leaf, so the plant remains healthy. Dickman believes the host plant and the fungus communicate during this initial meeting. The fungus is looking for a place to eat and reproduce. "When the fungus lands on a plant, it recognizes `This is a place where I can do business,' and the plant immediately responds with a yes or no."

How do the plant and fungus communicate? He thinks genes and the proteins they code for are the signals in plant-fungus communication. Understanding how they work means deciphering the molecular world of genes, proteins, and DNA, a...