Receptor-like proteins (RLPs) involved in disease resistance are cell surface receptors that perceive microbial patterns and trigger plant immunity. RLPs lack an intracellular kinase domain and they constitutively interact with the receptor-like kinase (RLK) SOBIR1 (Liebrand et al. (2014) TiPS 19:123–132). Cf-4 and Cf-9 are RLPs providing resistance to the fungal tomato pathogen Cladosporium fulvum. These Cf proteins form a constitutive complex with SOBIR1 (Liebrand et al. (2013) PNAS 110:10010-10015) and recruit SERK3 (BAK1) and SERK1 upon their activation by the matching effectors (Postma et al. (2016) New Phytol. DOI:10.1111/nph.13802). SOBIR1 contains a typical “glycine zipper” (GxxxGxxxG) and we found that this motif is essential for the interaction with RLPs (Bi et al. (2015) Mol. Plant Pathol. 17:96-107), which also contain such a motif in their trans-membrane domain. Interestingly, Arabidopsis SOBIR1 shows auto-activity in tobacco and we observed that this feature is SERK-dependent and also requires the glycine zipper. By co-immunoprecipitation experiments we have been able to show that a bacterial type III-secreted effector targets SOBIR1, thereby inhibiting its auto-activity. We have generated tyrosine mutants in the kinase domain of SOBIR1 that affect auto-activity and will be informative for elucidating whether SOBIR1, in addition to being a binding scaffold for RLPs, is also involved in phosphorylation processes initiating defense signaling. Future studies will focus on (1) the role of the glycine zippers, which are also present in the SERKs, in (tripartite) complex formation; (2) potential differential phosphorylation of SOBIR1 upon activation of the associated RLP by ligand recognition; (3) the precise impact on SOBIR1 function upon its targeting by a bacterial effector and (4) the identification of (cytoplasmic) signaling proteins that are recruited downstream of the Avr4/Cf-4/SOBIR1/SERK complex.
|Publication status||Published - 30 Nov 2016|
|Event||XVII International Congress on Molecular Plant-Microbe Interactions - Portland, Oregon, United States|
Duration: 17 Jul 2016 → 21 Jul 2016
|Conference||XVII International Congress on Molecular Plant-Microbe Interactions|
|Period||17/07/16 → 21/07/16|
Joosten, M. H. A. J., van der Burgh, A. M., & Wu, J. (2016). SOBIR1 plays a central role in signaling by receptor-like proteins. 463. Abstract from XVII International Congress on Molecular Plant-Microbe Interactions, Portland, Oregon, United States. http://www.ismpmi.org/congress/2016/abstracts/pages/abstractdetail.aspx?lid=463