Scientists Find New Tool for Pathogen to Pillage Plants

Bacteria have a variety of tricks to avoid detection when plundering a plant cell. According to researchers from Boyce Thompson Institute and the USDA-Agricultural Research Service, a protein from Pseudomonas syringae – AvrPtoB – suppresses the immune response of plants. AvrPtoB prevents the plant from detecting another bacterial protein, HopAD1, which helps the bacterium to reproduce unnoticed.

P. syringae infects a wide variety of plants. It launches an infection by sticking a needle-like tube into the plant cell and injecting proteins called effectors that disable plant defense. Over time, bacteria evolve new effector proteins, while the plant acquires new defense proteins to uncover and respond to the attack.

Plants have two lines of defense for fighting off bacteria. The first defense is called pattern-triggered immunity (PTI), while the second is called effector-triggered immunity (ETI). ETI ultimately results in the plant killing off its own affected cells. Previous studies have shown that AvrPtoB blocks two plant defense proteins, Pto and Fen, which helps the bacterium to evade ETI. The researchers found that HopAD1 could trigger ETI. They also discovered a previously hidden phenomenon: AvrPtoB can mask the detection of HopAD1 by disabling the MKK2 protein, which the cell needs to trigger ETI.

For more details, read the news release at the BTI website.