Shredding dead cells for protection
Interestingly microbes are not colonising the root tip. Now researchers show in eLife that is because the tip protecting root cap is actively shredding death cells.
Microbes are actively colonising plant roots. Except the growth centre containing tip of the root, which stays free of microbes. The root tip is surrounded by the root cap. Which consist of cells that die in a controlled manner and subsequently are released from the root. The researchers asked themselves how this controlled dying contributes to the protection of the growth centre against infection.
In order to study this the researchers turned to mutants in which the root cap cells did not die in an controlled manner. The roots of these plants have an untidy accumulation of dead cells along the outside of the root.
The shredding of dead cells deprives infecting fungi of nutrients
But especially noticeable was the increased infection by a good natured fungi. Normally this fungi induces extra root growth. But in the mutants while the fungus growth increased, it took longer for the benefits on root growth to kick in.
Closer studying of the growth of the fungus on the mutant roots showed that the fungus fed itself with the dead cells that still sticked to the root. Those cells gave the fungus extra nutrients.
Lastly the researchers studied the effect of the good natured fungus on the genes that regulate the controlled cell death. In presence of the fungus, those genes were less active.
It appears that the root cap cells protect the tip of the root from infection through the actively shredding of its dead cells. Preventing infecting microbes from getting easy nutrients at the root tip. At the same time the microbes actively try to influence the root cap cells to keep their dead sisters near, So that they can get a hold on the root via those dead cells.
Literature
Nyasha Charura, Ernesto Llamas, Concetta De Quattro, David Vilchez, Moritz K Nowack, and Alga Zuccaro (2024) Root cap cell corpse clearance limits microbial colonization in Arabidopsis thaliana. eLife 13:RP96266. https://doi.org/10.7554/eLife.96266.3
Plant en Zo 