Plant & zo
The science of plants and more
Extra root growth through infection
Nematodes that infect plants can cause lots of damage. These parasites infect the plants through their roots. When inside, they work their way up to the vascular bundle, were they start feeding. Plants are growing more roots around the infection site, as a way of compensating. But up to now it was unclear how the secondary root growth is induced by nematode infection. A team of Dutch researchers found out.
The researchers counted the number of secondary roots and nematode infections to analyse the correlation between root growth and nematodes. It turned out that with increasing numbers of infections the numbers of secondary roots also increased. But whereby uninfected plants the secondary roots were evenly distributed over the main root, this was not so by infected roots. There the secondary roots clustered around the infection site.
To analyse why, the researchers turned to infection and wound manager JA and its worker ERF109. The amount of JA as well as that of ERF109 increased at the start of the infection. But ERF109 only increased when the plant could sense JA. When the plant couldn’t observe JA, ERF109 was absent. Then it turned out, fewer secondary roots were formed as a reaction in an infection by the plant. Showing that ERF109 is needed for the production of extra roots at the site of infection.
Showing that ERF109 locally initiates auxin production
Subsequently, the researchers studied ERF109. ERF109 its job is to turn on genes for the production of the root growth manager auxin. Is ERF109 present, then the researchers observed extra auxin at the site of infection, but not so in absence of ERF109.
To exclude that auxin originated somewhere else the researchers blocked auxin production in either the shoot, roots or in the whole plant. This showed that blocking auxin production in the shoot did not result in any difference in root growth. But when they blocked auxin production in the roots or in the whole plant, then the plant was not producing extra secondary roots after an infection. Showing that ERF109 locally initiates auxin production.
The study showed that extra root growth at the site of infection is directly caused by the infection. The plant’s reaction caused by the infections initiates local extra auxin production, what in turn stimulates extra root growth. Making it a deliberate reaction of the plant to compensate its primary root growth loss caused by the infection.
Guarneri, N., Willig, J.-J., Sterken, M.G., Zhou, W., Hasan, M.S., Sharon, L., Grundler, F.M.W., Willemsen, V., Goverse, A., Smant, G. and Lozano-Torres, J.L. (2023) Root architecture plasticity in response to endoparasitic cyst nematodes is mediated by damage signaling. New Phytol, 237: 807-822. https://doi.org/10.1111/nph.18570