Populus trichocarpa encodes small, effector-like secreted proteins that are highly induces during mutualistic symbiosis

Jonathan M. Plett,Hengfu Yin,Ritesh Mewalal,Rongbin Hu,Ting Li,Priya Ranjan,Sara Jawdy,Henrique C. De Paoli,George Butler,Tessa Maureen Burch-Smith,Hap-Bo Guo,Chun Ju Chen,Annegret Kohler,Ian C. Anderson,Jessy L. Labbé,Francis Martin,Gerald A. Tuskan,Xiaohan Yang 2017 March 23 Scientific Reports 7(1): 382


During symbiosis, organisms use a range of metabolic and protein-based signals to communicate. Of these protein signals, one class is defined as ‘effectors’, i.e., small secreted proteins (SSPs) that cause phenotypical and physiological changes in another organism. To date, protein-based effectors have been described in aphids, nematodes, fungi and bacteria. Using RNA sequencing of Populus trichocarpa roots in mutualistic symbiosis with the ectomycorrhizal fungus Laccaria bicolor, we sought to determine if host plants also contain genes encoding effector-like proteins. We identified 417 plant-encoded putative SSPs that were significantly regulated during this interaction, including 161 SSPs specific to P. trichocarpa and 15 SSPs exhibiting expansion in Populus and closely related lineages. We demonstrate that a subset of these SSPs can enter L. bicolor hyphae, localize to the nucleus and affect hyphal growth and morphology. We conclude that plants encode proteins that appear to function as effector proteins that may regulate symbiotic associations.


Figure 1
Characteristics of Populus trichocarpa genes differentially expressed during mutualistic symbiosis with Laccaria bicolor. (a) A computational pipeline for discovery of small protein-encoding genes in P. trichocarpa in response to L. bicolor. (b) Sequence length distribution of P. trichocarpa computationally-predicted secreted proteins expressed during mutualistic symbiosis with L. bicolor. ‘Small’ proteins are defined as ≤250 amino acids.


Plett, J. M., H. Yin, R. Mewalal, R. Hu, T. Li, P. Ranjan, S. Jawdy, H. C. De Paoli, G. Butler, T. M. Burch-Smith, H.-B. Guo, C. Ju Chen, A. Kohler, I. C. Anderson, J. L. Labbé, F. Martin, G. A. Tuskan and X. Yang (2017). "Populus trichocarpa encodes small, effector-like secreted proteins that are highly induced during mutualistic symbiosis." Scientific Reports 7(1): 382.