Clathrin-mediated endocytosis of RxLR effectors into plant cells

Wang et al. discover that Phytophthora infestans RxLR effectors enter host plant cells via clathrin-mediated endocytosis.

By Haixia Wang¹, Petra C Boevink², Paul RJ Birch^1,2

¹Division of Plant Science, School of Life Sciences, University of Dundee, @James Hutton Institute, Errol Road, Invergowrie, Dundee DD2 5DA, UK.

²Cell and Molecular Sciences, James Hutton Institute, Errol Road, Invergowrie, Dundee DD2 5DA, UK.

Background: Disease causing oomycete pathogens, such as Phytophthora infestans, the cause of potato late blight, represent a threat to global food security. To establish disease P. infestans delivers virulence proteins called ‘RxLR’ effectors into living plant cells. RxLR effectors target host proteins and processes and manipulate them to suppress immunity.

Question: A key question addressed in our work is: are RxLR effectors taken up into plant host cells by clathrin-mediated endocytosis?

Findings: We explored whether clathrin-mediated endocytosis (CME) is involved in RxLR effector uptake in three ways. Firstly, we silenced key host components, clathrin itself and a RAB protein called Ara6, and found that both P. infestans infection and RxLR effector delivery into host cells were reduced. Secondly, we used labelled clathrin and Ara6 proteins to immunopurify endosomal vesicles from plant cells during infection and found that a tagged RxLR effector was co-purified. Thirdly, we again captured endosomal vesicles during infection and performed a proteomics study, demonstrating that RxLR effectors, but not ‘apoplastic’ effectors that function outside of plant cells, were associated with the purified endosomes.

Next steps: Uptake of RxLR effectors into plant cells by CME implies that, although inside the host cells, the effectors are nevertheless compartmentalised in membrane vesicles. How do they escape the confines of the endomembrane system to reach their host target proteins in different subcellular locations?

Reference:

Haixia Wang, Shumei Wang, Wei Wang, Lin Xu, Lydia RJ Welsh, Marek Gierlinski, Stephen C Whisson, Piers A Hemsley, Petra C Boevink, Paul RJ Birch. (2023). Uptake of oomycete RXLR effectors into host cells by clathrin-mediated endocytosis. https://doi.org/10.1093/plcell/koad069