Plants dig deep in times of change

11 July 2002
ENGINEERING plants that are more resistant to disease and changing climatic conditions, among other things, remains the perennial pursuit of scientists around the globe, and this quest is at the heart of work being done by Masters graduands Lindsay Petersen and Yu-Hung "Linda" Wei.

Petersen and Wei are the first Masters students to graduate from the lab of Dr Katherine Denby of the Department of Molecular and Cell Biology, whose work focuses on plant signalling. Studying the "model plant", Arabidopsis thaliana, Denby and her postgraduate researchers look specifically at the signalling mechanisms that kick in following infection by pathogens or some other change in a plant's "environment".

"We study how plants know something has changed, and how they adapt to those changes," says Denby.

In her thesis on Differential display identifies jasmonate-responsive genes in Arabidopsis thaliana, Wei concentrated on the work of signalling molecules called jasmonates. In this "signalling pathway", jasmonates induce the release of a number of a plant's defence genes, she explained.

Wei discovered that one of the genes generated by jasmonic acids is a plant enzyme called myrosinase. When an insect bites the leaf of the plant, the myrosinase breaks down glucosinolates that release cyanide compounds that repel the insect.

The exact pathway still has to be mapped, however, and is fertile ground for further research.

In turn, Petersen's work took the form of An investigation into the role of cytosolic-free calcium in salicylic acid mediation of disease resistance in Arabidopsis thaliana, in which she studied the role that salicylic acids play in the plant's defence mechanism. Previous research has shown that when a pathogen infects a plant, there is an increase in salicylic acid.

A plant can be made resistant to a disease by mimicking this pathway, i.e. that by giving the plant a dose of salicylic acid it will go through the defence reaction without introducing the pathogen, says Petersen. The "cool thing" about this research, adds Denby, is the reporter molecule, an aequorin gene, they use to measure the calcium in the plant (calcium levels change because of the salicylic acid).

"The aequorin gene comes from jellyfish and we use Arabidopsis plants containing this gene," explains Denby. "Anytime calcium levels increase, the plants emit light." Both students received distinctions for their theses, and deservedly so, comments Denby. "They're very interested in what they're doing, and very rigorous."

Arabidopsis is a hot topic of plant signalling, she notes, and Wei and Petersen's work can be put to good use in biotechnology strategies to develop plants that are more resistant to disease and other onslaughts. "They are answering questions which are of interest worldwide," Denby points out.

Wei and Petersen are still working in Denby's lab, having decided to make their Masters' findings the foundation for their doctoral studies. They're also very keen to continue working with Denby, to whom, they say, they can "relate".

"She's great," they eulogise with a synchronised burst of laughter.

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