by Laura Davies
I’m Dr. Laura Davies and I’m a postdoc with CSIRO Agriculture in the lab of Dr. Ian Dry along with Ange Jermakow and Nayana Arunasiri. I’m going to show you some of the research we do, investigating the weird and wonderful world of plant parasites here at Wine Innovation West on the Waite campus. We are a molecular biology lab, which means we work on understanding what is happening at the DNA and protein level.
Our research focuses on two diseases of grapevine: powdery mildew and downy mildew which cost the Australian wine industry $140 million every year. Even low levels of disease cause severe reductions in the yield and quality of berries, which affects the quality of wine produced. Powdery mildew is caused by the fungal parasite Erysiphe necator and is a problem in most growing seasons whilst wet conditions favour the growth of downy mildew caused by Plasmopara viticola.
Cultivated grapevine (Vitis vinifera) is unable to protect itself against these parasites because it evolved on a different continent to the parasites, and hasn’t evolved the specialised genes it requires to kill the parasites using the plant’s own immune system. This means growers need to apply huge amounts of fungicides to prevent an outbreak of disease. In Europe grapevines account for ~6 % of total crop area but ~70 % of all fungicide usage. In recent years Europe has been working to reduce fungicide use and the research we do in our lab is assisting Australian efforts to do the same.
Our lab is trying to reduce the need for fungicide applications by giving a ‘super boost’ to cultivated grapevine’s immune system. We have discovered wild species of grapevine that evolved alongside the parasites in North America that have specialised resistance genes which enable grapevines to recognise specific proteins secreted by the parasite to help cause infection. Once the presence of the parasite proteins are detected, the grapevine’s immune system switches on, leading to the death of the plant cell the parasite is trying to invade. As growth of the parasite is completely dependent on nutrition derived from the plant, death of the plant cell also leads to the death of the parasite.
By using flowers from the wild species to pollinate flowers of cultivated varieties, such as Shiraz, we have been able to move these resistance genes from the wild grapevine species into varieties used for winemaking.
Our lab is generating a number of new varieties that contain resistance genes effective against powdery and downy mildew and there are plans to make these varieties commercially available.
In addition to researching resistance genes, we are also interested in susceptibility genes. These are plant genes that are essential for parasites to successfully infect plant cells. Only a small number of susceptibility genes have been identified but one gene, known as MLO, is required for powdery mildew infection. Plants without a working version of the MLO gene do not develop powdery mildew disease – these plants have lost their susceptibility to the parasite.
We have identified MLO genes in grapevine and part of our research involves working out how they function and contribute to powdery mildew susceptibility.
My research is also focused on understanding how E. necator infects grapevine and causes powdery mildew disease. Our research indicated that it does this by secreting many small proteins called ‘effectors’ into the plant, which reprogram many of grapevine’s processes.
Effector proteins are the key to understanding how microscopic parasites can reprogram complex and essential pathways in plant cells. Understanding which plant pathways are important for successful parasite infection also provides us with new targets for parasite control strategies.
Working as a research scientist can be highly challenging. However, working at Waite and performing world-class research in the company of excellent researchers and friends can also be incredibly rewarding.