Abstract
BackgroundLysin motif (LysM)-containing proteins are involved in the recognition of fungal and bacterial pathogens. However, few studies have reported on their roles in the defense responses of woody plants against pathogens. A previous study reported that the apple MdCERK1 gene was induced by chitin and Rhizoctonia solani, and its protein can bind to chitin. However, its effect on defense responses has not been investigated.ResultsIn this study, a new apple CERK gene, designated as MdCERK1–2, was identified. It encodes a protein that shares high sequence identity with the previously reported MdCERK1 and AtCERK1. Its chitin binding ability and subcellular location are similar to MdCERK1 and AtCERK1, suggesting that MdCERK1–2 may play a role in apple immune defense responses as a pattern recognition receptor (PRR). MdCERK1–2 expression in apple was induced by 2 fungal pathogens, Botryosphaeria dothidea and Glomerella cingulate, but not by the bacterial pathogen, Erwinia amylovora, indicating that MdCERK1–2 is involved in apple anti-fungal defense responses. Further functional analysis by heterologous overexpression (OE) in Nicotiana benthamiana (Nb) demonstrated that MdCERK1–2 OE improved Nb resistance to the pathogenic fungus, Alternaria alternata. H2O2 accumulation and callose deposition increased after A. alternata infection in MdCERK1–2 OE plants compared to wild type (WT) and empty vector (EV)-transformed plants. The induced expression of NbPAL4 by A. alternata significantly (p < 0.01, n = 4) increased in MdCERK1–2 OE plants. Other tested genes, including NbNPR1, NbPR1a, NbERF1, and NbLOX1, did not exhibit significant changes after A. alternata infection in OE plants compared to EV or WT plants. OE plants also accumulated more polyphenols after A. alternata infection.ConclusionsHeterologous MdCERK1–2 OE affects multiple defense responses in Nb plants and increased their resistance to fungal pathogens. This result also suggests that MdCERK1–2 is involved in apple defense responses against pathogenic fungi.
Highlights
Lysin motif (LysM)-containing proteins are involved in the recognition of fungal and bacterial pathogens
By aligning MdCERK1–2 with well-studied LysM-containing proteins, 7 residues that are crucial for NAG binding were found in LysM2, which are similar to the other reported LysM-containing proteins [14, 31] (Fig. 1b), suggesting that MdCERK1–2 can bind to NAG
These proteins are all involved in the defense against fungal pathogens [9, 19, 30], suggesting that MdCERK1–2 may be involved in the defense responses against fungal pathogen infection
Summary
Lysin motif (LysM)-containing proteins are involved in the recognition of fungal and bacterial pathogens. Few studies have reported on their roles in the defense responses of woody plants against pathogens. Plants first detect pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs), and initiate a series of rapid PAMP-triggered immunity (PTI) responses to limit the proliferation and spread of pathogens [1]. Upon binding to corresponding ligands, these PRRs initiate downstream defense responses, such as a transient influx of calcium ions, ROS bursts, MAPKs activation, and the increased expression of pathogenesis-related (PR) protein genes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
