Exploring the way of plant disease resistance: major discoveries in cell membran

Posted by Ilsa Miller on December 24th, 2020

Plants are the basis for human survival. They convert solar energy into chemical energy through photosynthesis and produce the oxygen we need. However, plants also face various threats and are attacked by phytopathogens such as viruses and bacteria, leading to illness or even death. Statistics show that plant pathogens cause huge losses to global crop production every year, and seriously threaten world food security.

In the long-term evolution, plants have formed a series of complex and ingenious mechanisms to sense threats and produce corresponding defense responses to prevent or eliminate pathogen invasion. This process not only includes simple identification, but also transmits identification signals in space and coordinates various responses.

Among them, the recognition and response to the signal occurs at the plant cell level. On the surface of plant cells, there is a cell membrane that isolates the internal and external environments of the cell. Therefore, plants need to perceive specific molecules through their cell membranes to understand the existence of potential external attackers, and send out “alerts”, which are transmitted to different compartments inside the cell, and finally reach the nucleus where genetic material is stored, and regulate the expression of plant disease resistance genes. As a plant's unique photosynthetic organelle, chloroplasts also play a central role in regulating the response of plants to stimuli, which is essential for plant survival.

For a long time, how this “alarm” information is transmitted intracellularly has become the focus of scientists' exploration in the plant field. Recently, good news came from China. The research team of Shanghai Plant Stress Biology Research Center, Excellent Innovation Center for Molecular Plant Science, Chinese Academy of Sciences, revealed an important signal transmission pathway connecting cell membranes and chloroplasts, and the relevant results have been published in Cell.

The study reveals how some plant proteins associate with the cell membrane and how they are transferred from the cell membrane to the interior of the chloroplast when sensing the presence of pathogens, “warning” that chloroplasts are threatening. Immediately afterwards, chloroplasts transmit this information to the nucleus through a “retrograde signal transmission” process, which regulates disease resistance gene expression and activates defense to fight invaders. This pathway is one of the strategies for plant cells to transmit danger signals from the outside world to the chloroplast, which can rapidly, timely, and accurately integrate signals and produce appropriate downstream responses.

Plant pathogens and their hosts have long been in co-evolution resembling an “arms race”. The study found that pathogens can hijack this way of transmitting information inside plant cells. Some proteins from plant viruses and bacteria can cleverly “mimic” the above plant protein behavior, can bind to cell membranes, and can also move to chloroplasts when plant cells sense attack. Once inside the chloroplast, they impair the communication between the chloroplast and the nucleus, which hinders plant defense response activation and helps their own survival and reproduction.

It is also found that different types of pathogens have evolved similar strategies to achieve the purpose of inhibiting plant defense, which strongly proves that the signal transmission pathway connecting cell membrane and chloroplast plays a central role in the interaction between plants and microorganisms. This study provides a new idea for designing plant protection strategies and developing new resistant varieties.

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