How do plants fight off leaf curl disease?
A process that breaks down damaged or unwanted molecules inside cells can help protect plants from some viruses.
Plants use a variety of processes to protect themselves against viruses and other disease-causing microbes. Autophagy, for example, is a process that breaks down damaged or unwanted molecules found inside cells, which has also been linked to plant disease resistance. However, it is not precisely clear how autophagy helps plants to resist diseases, because this process seems to make plants more resistant to some disease-causing microbes but more susceptible to others.
Now, Yakupjan Haxim, Asigul Ismayil and colleagues show that autophagy helps to protect plants against three viruses belonging to the Geminiviridae family of plant viruses. One of these viruses causes an important disease in cotton plants, called cotton leaf curl disease. This virus can infect many other plant species, including a close relative of tobacco plants, called Nicotiana benthamiana, which is commonly used in plant biology experiments. Haxim, Ismayil and colleagues show that one of proteins produced by this virus, one called βC1, interacts with a plant protein called ATG8 and is then sent to be broken down by autophagy. Further experiments then identified a mutation in this protein that stopped it interacting with ATG8. Viruses carrying this mutated form of βC1 caused more severe symptoms and replicated more in N. benthamiana plants.
Interfering with autophagy made the N. benthamiana plants less resistant to the cotton leaf curl disease virus, and to two other geminiviruses that often infect tomatoes. Activating autophagy had the opposite effect, and made the plants more resistant to all three viruses.
Together these findings provide direct evidence that autophagy helps to defend plants against a number of viruses, by degrading one or more viral proteins in the plants. In the future, researchers may be able to build on these findings to engineer crop plants to be more resistant to viruses.
To find out more
Read the eLife research paper on which this eLife digest is based: “Autophagy functions as an antiviral mechanism against geminiviruses in plants” (February 28, 2017).
