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.
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.
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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