Requirement for the induced expression of a cell wall associated receptor kinase for survival during the pathogen response

TLDR

Pathogen infection in angiosperms depends on extracellular matrix interactions and signaling, and the Arabidopsis cell wall–associated receptor kinase Wak1 spans the plasma membrane with an ECM‑bound N‑terminus and a cytoplasmic kinase domain. Induction of Wak1 requires the positive regulator NPR1/NIM1. Wak1 is induced by pathogen infection and salicylate signaling, functions as a pathogen‑related protein, and its induced expression is essential for survival under INA; ectopic expression of Wak1 or its kinase domain confers resistance to lethal SA levels, linking ECM‑mediated signaling to protection against pathogen‑response damage.

Abstract

Pathogen infection of angiosperms must rely on some interaction between the extracellular matrix (ECM) and the invading agent, and may be accompanied by signaling between the ECM and cytoplasm. An Arabidopsis cell wall associated receptor kinase (Wak1) has an amino-terminal domain that is tightly associated with the ECM, spans the plasma membrane and has a cytoplasmic protein kinase domain. Wak1 expression is induced when Arabidopsis plants are infected with pathogen, or when the pathogen response is stimulated either by exogenous salicylate (SA) or its analog 2,2-dichloroisonicotinic acid (INA). This Wak1 induction requires the positive regulator NPR1/NIM1. Thus Wak1 is a pathogen-related (PR) protein. Expression of an antisense and a dominant negative allele of Wak1 shows that induced expression of Wak1 is needed for a plant to survive if stimulated by INA. Ectopic expression of the entire Wak1, or the kinase domain alone, can provide resistance to otherwise lethal SA levels. These experiments suggest that Wak1 expression and other PR proteins are protecting plants from detrimental effects incurred during the pathogen response. These results provide a direct link between a protein kinase that could mediate signals from the ECM, to the events that are precipitated by a pathogen infection.