2024-01-03 10:30:26
Plant cells are all surrounded by a rigid wall, one of the functions of which is to resist the very high pressure inside. Scientists have managed to decipher how they manage to grow, while maintaining the rigidity of this wall. This discovery should have multiple applications.
Plants are able to use solar energy to convert atmospheric CO2 into sugars. Inside, all the cells are filled with water and sugars and are put under pressure; we talk regarding turgor. This pressure is very important, because it can reach up to 10 times that of the atmosphere. To maintain their integrity, the cells are all surrounded by a rigid wall that serves as both a protective barrier and support for the plant’s skeleton. Until now, the scientific community did not understand how cells managed to grow while maintaining the rigidity of their walls. Researchers from INRAE and CNRS, in collaboration with Swiss and Belgian teams, managed to uncover this secret and published their work in the journal Science.
The wall is made up of cellulose fibers surrounded by a matrix composed of several polysaccharides, including pectins. These pectins are polymers synthesized in the cell, in the methylated form, that is to say having CH3 groups, then secreted into the wall. Inside this wall, enzymes, more precisely pectin methylesterases, are also present and modify this polymer, by removing its methyl groups, so that it becomes an acid carrying a negative charge. This demethylation has the effect of causing the wall to swell and this therefore contributes to the growth of the cell.
To understand how this wall can grow while maintaining its rigidity, scientists were interested in the growth of the pollen tube of the lady’s cress, a plant widely studied in research, both biological and genetic. This pollen tube is made up of a slender structure that grows from a pollen grain. Unlike the cells of a tissue, the cells inside are isolated and also have one of the fastest growth rates in the living world, which allows them to be analyzed more easily.
The study of the pollen tube has made it possible to demonstrate that a family of peptides, that is to say small proteins made up of a chain of around fifty amino acids, is involved in the assembly mechanism. of the wall. It is produced by the plant and is secreted at the same time as pectins. It appears that these peptides have the particularity of carrying positive charges and combining with a protein, called “ LRX8” and heree in the wall, to create a complex, which exposes these positive charges on its surface.
Result: when the pectins are demethylated (lose their CH3 groups) and they begin to swell because of their negative charge, they then find themselves facing this positively charged complex. In vitro, the researchers then observed that this interaction has the effect of condensing the pectins, their structure becomes cross-linked, and this has the effect of giving rigidity to the wall.
Better predict plant behavior in the face of climate change
“Until now, it was thought that the wall was organized through interactions between polysaccharides, reveals Herman Höfte, research director at Inrae. Through our work, we demonstrate that an interaction occurs with a protein, at the same time as the wall forms and grows, and that this allows it to resist turgor in the cell. This is a result of fundamental research which should then be found in biology textbooks. »
This discovery should have multiple applications. It will now be possible to model the mechanism of plant growth more precisely, and thus predict with less uncertainty the way in which they will behave in the face of changes in their environment, particularly climatic changes. In the field of quantitative genetics, identifying parts of the genome that have favorable effects on plant growth and determine future crop yields should also be easier to achieve.
“Our work should also have repercussions in the field of plant immunity, that is to say on the way in which they manage to resist pathogens, fungi and bacteria which attack plants through their wallsadds the researcher. By studying the mechanism in a very fundamental way, we begin to understand how the plant defends itself. Ultimately, we should be able to select plants that have more effective cell wall modification strategies than others in order to reduce the use of fungicides. »
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