Abstract
Plants depend on both preformed and inducible defence responses to defend themselves against biotic stresses stemming from pathogen attacks. In this regard, plants perceive pathogenic threats from the environment through pattern recognition receptors (PRRs) that recognise microbe-associated molecular patterns (MAMPs), and so induce plant defence responses against invading pathogens. Close to thirty PRR proteins have been identified in plants, however, the molecular mechanisms underlying MAMP perception by these receptors/receptor complexes are not fully understood. As such, knockout (KO) of genes that code for PRRs and co-receptors/defence-associated proteins is a valuable tool to study plant immunity. The loss of gene activity often causes changes in the phenotype of the model plant, allowing in vivo studies of gene function and associated biological mechanisms. Here, we review the functions of selected PRRs, brassinosteroid insensitive 1 (BRI1) associated receptor kinase 1 (BAK1) and other associated defence proteins that have been identified in plants, and also outline KO lines generated by T-DNA insertional mutagenesis as well as the effect on MAMP perception—and triggered immunity (MTI). In addition, we further review the role of membrane raft domains in flg22-induced MTI in Arabidopsis, due to the vital role in the activation of several proteins that are part of the membrane raft domain theory in this regard.
Highlights
The primary defence response of plants is achieved through the perception of conserved signatures referred to as microbe-associated molecular patterns (MAMPs) by pattern recognition receptors (PRRs), localised in the plasma membrane, which leads to MAMP-triggered immunity (MTI) [8,9] (Figure 1)
MAMPs reveal the presence of pathogenic microbes, leading to the activation and upregulation of basal defence responses in plants
We reviewed the role that membrane raft domains play, in which PRRs have been suggested to be localised during the perception response, using flg22-mediated PRR-dependent reactive oxygen species (ROS) production in MTI as an example to set the stage for subsequent KO studies
Summary
Plants are continuously exposed to pathogen attack and this may lead to global losses in crop yields that, in turn, affect food security worldwide [1]. The primary defence response of plants is achieved through the perception of conserved signatures referred to as microbe-associated molecular patterns (MAMPs) by pattern recognition receptors (PRRs), localised in the plasma membrane, which leads to MAMP-triggered immunity (MTI) [8,9] (Figure 1). These plant PRRs mostly belong to the receptor-like kinase (RLKs) or receptor-like protein (RLPs) families. The details, of the molecular mechanisms underlying MAMP perception by plant PRRs are elusive and appear to be different in each case, due to the unique physico-chemical properties of each ligand, with regard to the binding kinetics and associated responses of the ligand: receptor interactions
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