Abstract
Pathogen‐associated molecular patterns (PAMPs) are recognized by pattern recognition receptors (PRRs) localized on the host plasma membrane. These receptors activate a broad-spectrum and durable defense, which are desired characteristics for disease resistance in plant breeding programs. In this study, candidate sequences for PRRs with lysin motifs (LysM) were investigated in the Coffea arabica genome. For this, approaches based on the principle of sequence similarity, conservation of motifs and domains, phylogenetic analysis, and modulation of gene expression in response to Hemileia vastatrix were used. The candidate sequences for PRRs in C. arabica (Ca1-LYP, Ca2-LYP, Ca1-CERK1, Ca2-CERK1, Ca-LYK4, Ca1-LYK5 and Ca2-LYK5) showed high similarity with the reference PRRs used: Os-CEBiP, At-CERK1, At-LYK4 and At-LYK5. Moreover, the ectodomains of these sequences showed high identity or similarity with the reference sequences, indicating structural and functional conservation. The studied sequences are also phylogenetically related to the reference PRRs described in Arabidopsis, rice, and other plant species. All candidates for receptors had their expression induced after the inoculation with H. vastatrix, since the first time of sampling at 6 hours post‐inoculation (hpi). At 24 hpi, there was a significant increase in expression, for most of the receptors evaluated, and at 48 hpi, a suppression. The results showed that the candidate sequences for PRRs in the C. arabica genome display high homology with fungal PRRs already described in the literature. Besides, they respond to pathogen inoculation and seem to be involved in the perception or signaling of fungal chitin, acting as receptors or co-receptors of this molecule. These findings represent an advance in the understanding of the basal immunity of this species.
Highlights
The interaction between plants and pathogens can be understood as a co-evolutionary “molecular war,” in which each opponent uses their biological weapons as necessary, causing a successful infection by the pathogen or resistance in the host [1]
These receptors are membrane proteins that usually have an extracellular domain involved in the perception of the ligand, the transmembrane or glycosylphosphatidylinositol (GPI) anchor domain that anchors the protein in the plasma membrane, and an intracellular kinase domain that is involved in the defense response signaling [4]
Two candidate sequences were selected for LYK4 (Scaffold 612.376 and 952.320) and LYK5 (Scaffold 628.522 and 1841.91) (Fig 1B and 1D and S1 Table) and four ones for CERK1 (Scaffold 539.592, 1805.113, 2193.164 and 476.38) (Fig 1A and S1 Table)
Summary
The interaction between plants and pathogens can be understood as a co-evolutionary “molecular war,” in which each opponent uses their biological weapons as necessary, causing a successful infection by the pathogen or resistance in the host [1]. The PAMPs recognition is performed by pattern recognition receptors (PRRs) These receptors are membrane proteins that usually have an extracellular domain involved in the perception of the ligand, the transmembrane or glycosylphosphatidylinositol (GPI) anchor domain that anchors the protein in the plasma membrane, and an intracellular kinase domain that is involved in the defense response signaling [4]. Adapted pathogens can suppress this first line of defense by secreting specific effectors In response to this suppression, R proteins, encoded by resistance genes, recognize these effectors triggering ETI [5]. In spite of identifying different ligands, ETI and PTI lead to similar signaling pathways [6] This signaling involves changes in calcium levels in the cytoplasm, production of reactive oxygen species (ROS) and signaling cascades involving protein kinases, MAPKs (mitogen-activated protein kinases) and CDPKs (calcium-dependent protein kinases) [7–10]
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