Record ID No. |
3959 |
Author(s) |
Meritxell Antolín-Llovera, Martina K. Ried, Martin Parniske , 2014 |
Affiliation |
Genetics, Faculty of Biology, University of Munich (LMU), Großhaderner Straße 4, 82152 Martinsried, Germany, email: (Martin Parniske) |
Title |
Cleavage of the SYMBIOSIS RECEPTOR-LIKE KINASE Ectodomain Promotes Complex Formation with Nod Factor Receptor 5 |
Source. Vol.(no):Page |
Current Biology 24(4): 422–427p. |
Categories |
Arbuscular Mycorrhiza |
Subjects |
Biochemistry |
Host |
Plants |
Organism |
Xenopus laevis, Arbuscular Mycorrhiza |
Country |
Germany, Western Europe |
Abstracts |
Plants form root symbioses with fungi and bacteria to improve their nutrient supply. SYMBIOSIS RECEPTOR-LIKE KINASE (SYMRK) is required for phosphate-acquiring arbuscular mycorrhiza, as well as for the nitrogen-fixing root nodule symbiosis of legumes [1] and actinorhizal plants [2,3], but its precise function was completely unclear. Here we show that the extracytoplasmic region of SYMRK, which comprises three leucine-rich repeats (LRRs) and a malectin-like domain (MLD) related to a carbohydrate-binding protein from Xenopus laevis [4], is cleaved to release the MLD in the absence of symbiotic stimulation. A conserved sequence motif—GDPC—that connects the MLD to the LRRs is required for MLD release. We discovered that Nod factor receptor 5 (NFR5) [5,6,7,8] forms a complex with the SYMRK version that remains after MLD release (SYMRK-ΔMLD). SYMRK-ΔMLD outcompeted full-length SYMRK for NFR5 interaction, indicating that the MLD negatively interferes with complex formation. SYMRK-ΔMLD is present at lower amounts than MLD, suggesting rapid degradation after MLD release. A deletion of the entire extracytoplasmic region increased protein abundance, suggesting that the LRR region promotes degradation. Curiously, this deletion led to excessive infection thread formation, highlighting the importance of fine-tuned regulation of SYMRK by its ectodomain. |