A plant receptor-like kinase required for both bacterial and fungal symbiosis

Abstract

Most higher plant species can enter a root symbiosis with arbuscular mycorrhizal fungi, in which plant carbon is traded for fungal phosphate. This is an ancient symbiosis, which has been detected in fossils of early land plants. In contrast, the nitrogen-fixing root nodule symbioses of plants with bacteria evolved more recently, and are phylogenetically restricted to the rosid I clade of plants. Both symbioses rely on partially overlapping genetic programmes. We have identified the molecular basis for this convergence by cloning orthologous SYMRK ('symbiosis receptor-like kinase') genes from Lotus and pea, which are required for both fungal and bacterial recognition. SYMRK is predicted to have a signal peptide, an extracellular domain comprising leucine-rich repeats, a transmembrane and an intracellular protein kinase domain. Lotus SYMRK is required for a symbiotic signal transduction pathway leading from the perception of microbial signal molecules to rapid symbiosis-related gene activation. The perception of symbiotic fungi and bacteria is mediated by at least one common signalling component, which could have been recruited during the evolution of root nodule symbioses from the already existing arbuscular mycorrhiza symbiosis.

A Ubiquitin Ligase of Symbiosis Receptor Kinase Involved in Nodule Organogenesis

“…SymRK is believed to function in both NF perception and downstream signal transduction, and is required for the earliest detectable root hair responses (Endre et al, 2002;Stracke et al, 2002). However, little is known about how SymRK transduces the NF signal to downstream components.…”

“…japonicus SymRK is known to play a role in IT initiation (Stracke et al, 2002). We scored IT numbers in SIE3 RNAi hairy roots 8 d after rhizobial inoculation.…”

“…The SymRK gene is indispensable for root endosymbiosis with rhizobia and arbuscular mycorrhizal fungi in legumes, and may function at the junction of rhizobial and fungal signaling cascades (Endre et al, 2002;Stracke et al, 2002). The SymRK protein contains a signal peptide sequence for protein sorting, an extracellular region for interacting with unidentified signal molecules, a transmembrane segment for anchoring to the plasma membrane, and an intracellular protein kinase domain (Endre et al, 2002;Stracke et al, 2002;Mitra et al, 2004;Capoen et al, 2005).…”

Bridging Model and Crop Legumes through Comparative Genomics

“…DOES NOT MAKE INFECTION2 [DMI2] in M. truncatula, NORK in alfalfa, and SYM19 in pea). At the same time, the ortholog of L. japonicus (called symbiosis receptor-like kinase, or SYMRK), which is located in a syntenic region of M. truncatula, alfalfa, and pea, also was isolated (Stracke et al, 2002(Stracke et al, , 2004.…”

Does SUNN-SYMRK Crosstalk occur in Medicago truncatula for regulating nodule organogenesis?

“…6 Symbiosis Receptor Kinase (SYMRK), an upstream LRR-RLK of the Nod factor signaling pathway, is indispensible for nodule organogenesis. 21,22 Recently, we have demonstrated that overexpression of the intracellular kinase domain of SYMRK (SYMRK-kd) from M. truncatula or Arachis hypogaea in M. truncatula roots induces nodule organogenesis in the absence of rhizobia. 23 Spontaneous nodulation in presence of SYMRK-kd was 6-fold more than rhizobia induced nodulation supported by full length SYMRK in M. truncatula TR25 (symrk knock out) roots suggesting the importance of SYMRK ectodomain in regulating nodule number.…”