When the plant immune system detects the invasion of pathogenic bacteria, the plant immune receptor protein becomes active as a “sentry” and mobilizes the body to initiate an immune response. However, it has been a mystery how the plant immune receptor protein is activated, but a paper published in the international authoritative academic journal Nature on the evening of September 21 by Professor Wang Yuanchao’s team at Nanjing Agricultural University and Professor Chai Jijie’s team at Tsinghua University reveals for the first time how the cell membrane receptor protein recognizes pathogenic bacteria while inhibiting them from “doing evil”. “This provides new insights into the mechanisms of plant-pathogen interactions and is an important guide to improving broad-spectrum, durable disease resistance in crops.
The focus of this research is a pair of enemies: XEG1, the core pathogenic factor of pathogenic bacteria, and RXEG1, a plant cell membrane receptor protein.
Wang Yuanchao introduced that XEG1 is a class of glycosyl hydrolases widely found in a variety of pathogenic bacteria including bacteria, fungi and oomycetes, and induces an immune response in plants when pathogens invade a variety of plants such as soybean and tomato.
The plant cell membrane recognition receptor RXEG1 is the “outpost” for monitoring pathogenic bacteria, and when it recognizes the pathogenic factor XEG1, it activates the plant defense system and generates resistance to the pathogen.
The study first clarified how RXEG1 recognizes XEG1 as an “enemy”. When RXEG1 recognizes the pathogenic factor XEG1 at the outer end of the cell membrane, it binds to another receptor protein kinase, BAK1, and transmits the signal of pathogen invasion to the cell, activating the plant immune signal,” said Yan Wang, co-first author and corresponding author at Nanjing Agricultural University. “
RXEG1 not only activates the plant’s immune response, but also inhibits the activity of XEG1 in degrading the plant cell wall. Wang Yuanchao made an analogy, “XEG1 attacks plants by hydrolyzing enzyme activity, it has a pocket of enzyme activity, which is equivalent to an ammunition depot full of enzymes, and RXEG1 just happens to bind on XEG1’s pocket of enzyme activity, which is equivalent to blocking just at the door of XEG1’s ammunition depot, allowing XEG1 to ‘disarm ‘, that is, it inhibits the enzymatic activity of XEG1 and makes it ineffective.”
XEG1 is a prevalent and non-variable key factor in different pathogenic bacteria. “The pathogenic factor XEG1 is widely present in pathogenic bacteria of many plants such as soybean, wheat and cotton, and the plant cell membrane receptor protein RXEG1 can be used later to improve the broad-spectrum disease resistance of plants.” Yuanchao Wang foresees that in the future, it might also be possible to screen XEG1 inhibitors and plant immune activators of RXEG1 among a large number of compounds by artificial intelligence.
