Plant tissue infected with Phytophthora. Image credit: Li et al. (CC BY 4.0)
Just like animals, plants can become infected and diseased. Among the microbes that infect plants, one group tends to stand out. Named Phytophthora after the Greek for ‘the plant destroyer’, these fungus-like microbes cause diseases in many species of plant, including important food crops. These diseases are difficult to control, and as a result Phytophthora diseases cost the farming industry billions of dollars every year.
Effective control of Phytophthora diseases is likely to depend on scientists first gaining a better understanding of how these microbes infect plants. Also like animals, plants have an immune system to protect themselves from disease. Yet many disease-causing microbes make so-called effector proteins to overcome their hosts’ defenses. Previously in 2015, researchers reported that one effector made by a species known as Phytophthora sojae could suppress the immune system of soybean plants during the early stages of an infection. But it was not clear how the effector achieved this.
Now, Li et al., who include many of the researchers involved in the 2015 study, go on to show that the same effector, known as PsAvh52, helps P. sojae to infect soybean plants by interacting with a previously unknown soybean enzyme. The enzyme is a transacetylase, meaning it belongs to a group of enzymes that transfer a chemical marker called an acetyl group on to other molecules including proteins.
Li et al. went on to show that the PsAvh52 effector essentially hijacks the transacetylase enzyme, moving it to a location in the cell nucleus where it could chemically modify the proteins that package the soybean plant’s DNA. These chemical changes activate nearby genes that would have otherwise been switched off, and these incorrectly activated genes make the plant more susceptible to the infection.
By deciphering one of the strategies that helps P. sojae to infect soybean plants, Li et al. have uncovered two possible approaches that may help to get this plant disease under control. The findings highlight the effector PsAvh52 as a weapon that could be blocked; they also reveal the transacetylase enzyme as a vulnerable point in the plant that could be protected. The next step will be to explore if there are chemical or genetic means that can achieve either of these two goals.
