Extra auxin against stress
Microbes like, Pseudomonas, give plants a helping hand in stress situations. For a long time it was unknown how they do this. Now a team of international researchers show in Microbial Biotechnology how Pseudomonas this does.
Plants colonised by beneficial microbes perform better than their non-colonised neighbours in stress situations. The colonising fungi or bacteria influences the root architecture. Those roots have for example more root hairs or secondary roots. Those can in turn help with the uptake of nutrients in stress situations. But how microbes initiate those changes in the plant was up till now not clear.
In order to find out the researchers analysed the genome of two in the dessert residing beneficial Pseudomonas strains. They discovered that these bacteria contain genes for the production of auxin, a plant growth hormone.
Pseudomonas promotes the growth of extra root hairs
Subsequently, the researchers studied the effect of the colonisation by these bacteria strains on Arabidopsis, tale cress. After colonisation of the root the plant quickly got more root hairs. After a week the influence of the bacteria on the rest of the root was also noticeable. The main root was shorter, but got in turn more secondary roots.
Because the Pseudomonas bacteria produce auxin the researchers studied its effect on the colonised roots. For this they used a receptor that lights up in the presence of auxin. Using this the researchers noticed that there was more auxin present in colonised roots than in non-colonised roots.
By rearranging the auxin transport channels Pseudomonas influences root growth
But the influence of Pseudomonas goes further than just deliver extra auxin. So the researchers discovered when they studied the channels that enable the spread of auxin between cells. After colonisation these channels are reorganised. This reorganisation is required for the beneficial effect of Pseudomonas. In the absence of those auxin spreading channels the colonisation does not influence root growth.
As long as the researchers grew the plants under optimal circumstances they did not observe any difference in the weight between colonised and non-colonised plants. They both did just as well. But this changed when the researchers grew the plants in the presence of salt. Then the colonised plants grew a lot better than the non-colonised plants. With stress it helps to have a beneficial Pseudomonas colony in your roots.
Literature
Marasco, R., Mosqueira, M.J., Seferji, K.A., Al Romaih, S.M., Michoud, G., Xu, J. et al. (2024) Desert-adapted plant growth-promoting pseudomonads modulate plant auxin homeostasis and mitigate salinity stress. Microbial Biotechnology, 17, e70043. Available from: https://doi.org/10.1111/1751-7915.70043
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