Isolation and characterization of NgRLK1, a receptor-like kinase of Nicotiana glutinosa that interacts with the elicitin of Phytophthora capsici

Abstract

Elicitins, extracellular proteins from Phytophthora fungi, elicit a hypersensitivity response (HR), including systemic acquired resistance, in some plants. The elicitin capsicein (~10 kDa) was purified by FPLC from culture filtrates of P. capsici. Purified native and recombinant capsicein induced a hypersensitive response in leaves of the non-host plants Nicotiana glutinosa and Brassica rapa subsp. pekinensis. To search for candidate capsicein-interacting proteins from N. glutinosa, a yeast two-hybrid assay was used. We identified a protein interactor that is homologous to a serine/threonine kinase of the plant receptor-like kinase (RLK) group and designated it NgRLK1. The ORF of NgRLK1 encodes a polypeptide of 832 amino acids (93,490 Da). A conserved domain analysis revealed that NgRLK1 has structural features typical of a plant RLK. NgRLK1 was autophosphorylated, with higher activity in the presence of Mn2+ than Mg2+.

PAMP Signaling in Plant Innate Immunity

“…Extracellular NgRLK1 was found to interact with the elicitin capsicein. Capsicein was found to bind to the intracellular kinase domain of NgRLK1 (Kim et al 2010 ). NgRLK1 was more closely related to the protein kinase homologous to PR5 K from Arabidopsis thaliana than to the lectin-like receptor kinases.…”

“…Elicitins are small lipid binding proteins secreted by the oomycetes Phytophthora and Pythium (Bonnet et al 1996 ;Bourque et al 1999 ;Baillieul et al 2003 ;Qutob et al 2003 ;Kawamura et al 2009 ;Kim et al 2010 ). Elicitin genes have been cloned from Phytophthora infestans (Kamoun et al 1997a , b ), P .…”

“…cryptogea (Panabieres et al 1995), and P . capsici (Kim et al 2010 ). Elicitins are highly conserved 10-kDa proteins that are secreted in culture by all tested Phytophthora and Pythium species (Kamoun et al 1993a , b ;Pernollet et al 1993 a, b).…”

“…A PRR for the elicitin capsicein has been identifi ed in tobacco ( Nicotiana glutinosa ) and it was designated NgRLK1 (Kim et al 2010 ). NgRLK1 has a domain structure similar to that of all plant RLKs.…”

“…NgRLK1 was more closely related to the protein kinase homologous to PR5 K from Arabidopsis thaliana than to the lectin-like receptor kinases. It has been suggested that plant recognition of capsicein occurs in the extracellular and intracellular spaces (Kim et al 2010 ). NgRLK1 is a new type of plant RLK that recognizes capsicein (Kim et al 2010 ). 2.11.9 LeEIX1 and LeEIX2, the PRRs for the PAMP EIX Proteins…”