Swammerdam Institute for Life Sciences

Protein uptake mechanism that sabotages plant immune system explained

14 December 2016

A new step has been taken in the ongoing battle between pathogens and plant breeders. UvA researchers Frank Takken, Xiaotang Di and Harrold van den Burg of the Swammerdam Institute of Life Sciences have discovered the mechanism which pathogenic fungi use to channel proteins into host cells where they can sabotage the immune system of a plant.

Bacteria are able to inject these proteins called effectors directly into the cells of the host. Yet the manner in which other pathogens manage to do so remained unknown. The major question was whether this process was controlled by the plant or by the pathogen. The UvA researchers have now discovered that effector protein uptake by plant cells requires the presence of a pathogen; in the absence of the latter, the protein remains outside the cell and is unable to function.

Prime interest

This discovery is of prime interest because some effector proteins do not suppress plant immune resistance, inadvertently activating it instead. This is because some plants have immune receptors which are able to recognise these specific effectors. These receptors are present in the cell and are only activated after uptake of the related effector. Clever use of this insight that pathogens cause effector uptake allows them to be fought with their own weapons. By linking the plant immune system activation to the presence of a pathogen and thus effector uptake, the pathogen can be stopped in its tracks, before it can cause plant disease.

Plant pathogens are a serious threat to crops and responsible for harvest losses of anywhere up to 30%. To prevent disease, plant breeders are constantly searching wild plants for natural sources of resistance which can be genetically introduced into crop plants. Unfortunately this approach usually only works temporarily; the introduced resistance often loses power over time, sometimes within years, sometimes within decades. This is the cause of the continual arms race between plant breeders and pathogens.

Patent

Together with Innovation Exchange Amsterdam (IXA) the UvA researchers have applied for a patent on their discovery. This patent is important to plant breeders and embodies a new weapon in the ongoing battle against pathogens. It allows the very mechanism developed by pathogens to cause plant disease to be used to activate the natural plant immune resistance instead, bringing the pathogen to bay in the process.

Effector protein recognised-tomato-plants-SILS-Frank-Takken-1

The location of an effector protein recognised by a cognate intracellular immune receptor differs in these two tomato plants. In the upper plant the effector is outside the host cell and is not perceived by the immune system.

Effector protein recognised-tomato-plants-SILS-Frank-Takken-2

In this plant the effector is inside the host cell, causing an autoimmune phenotype.

Publicatie details

Di, X., Gomila, J., Ma, L., Van Den Burg, H. A. & Takken, F. L. W. Uptake of the Fusarium effector Avr2 by tomato is not a cell autonomous event. . Front. Plant Sci. 7:1915. , doi:doi: 10.3389/fpls.2016.01915 (2016).

Published by  Faculty of Science