Plant protein 'doorkeepers' block invading microbes, s...(immune systems. Rather than developing ...)

This type of innate immune system has two branches: one makes use of receptor proteins outside the cell to recognize specific molecular features of an invading microbe, while the other branch uses similar proteins within the cell to recognize an invading microbe during the infection process.

Up until now, scientists had identified only one protein, known as RIN4, which is able to regulate these two branches of the plant immune system in Arabidopsis. The protein is found in the permeable plasma membrane that encases the cell on the inside of the cell wall. It has been unclear exactly how the protein and the two branches of the immune system interact to trigger an immune response in the plant.

In studying the RIN4 protein, Coaker and her colleagues identified six previously uncharacterized proteins that can associate with RIN4 inside plant cells. One protein, called AHA1, was characterized in-depth and found to be key to the immune response in Arabidopsis plants.

AHA1 can act to regulate the opening and closing of tiny holes called stomata, found on the underside of the leaf. The stomata allow gases and water to pass in and out of the leaf. This is the same opening that allows bacteria and other invading microbes to gain entrance to the plant.

The stomata are each flanked by two guard cells, which control these vitally important portals to the leaf. When the guard cells swell, the stomata close. Conversely, when the water content of the guard cells decreases, the stomata open.

The six proteins identified in this study were found to be intricately involved with the biochemical processes that enable the plant to recognize and block out invading
'/>"/>