Lysin 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. In 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. Heterologous 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.

中文翻译：

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含有苹果LysM的蛋白质基因MdCERK1-2的过量表达赋予了本生烟草对病原真菌Alternaria alternata的抗性增强。

包含赖氨酸基序（LysM）的蛋白质与真菌和细菌病原体的识别有关。然而，很少有研究报道它们在木本植物对病原体的防御反应中的作用。先前的研究报道苹果MdCERK1基因是由几丁质和茄红枯菌诱导的，其蛋白质可以与几丁质结合。但是，尚未研究其对防御反应的影响。在这项研究中，鉴定了一个新的苹果CERK基因，命名为MdCERK1-2。它编码一种与先前报道的MdCERK1和AtCERK1具有高度序列同一性的蛋白质。它的几丁质结合能力和亚细胞位置类似于MdCERK1和AtCERK1，表明MdCERK1-2在苹果的免疫防御反应中可能作为模式识别受体（PRR）起作用。苹果中MdCERK1-2的表达是由2种真菌病原体，即灰葡萄孢和扣带菌诱导的，而细菌病原体，即淀粉小球藻则没有，这表明MdCERK1-2参与了苹果的抗真菌防御反应。通过对本氏烟草（Nb）进行异源过表达（OE）进行的进一步功能分析表明，MdCERK1-2 OE可以提高Nb对病原真菌链格孢菌（Alternaria alternata）的抗性。与野生型（WT）和空载体（EV）转化植物相比，MdCERK1-2 OE植物中交链孢霉感染后H2O2积累和ose质沉积增加。在MdCERK1-2 OE植物中，交链孢霉诱导的NbPAL4表达显着增加（p <0.01，n = 4）。其他测试的基因，包括NbNPR1，NbPR1a，NbERF1和NbLOX1，在A后未表现出显着变化。与EV或WT植物相比，OE植物中的链霉菌感染。交配农杆菌感染后，OE植物也积累了更多的多酚。异源MdCERK1-2 OE影响Nb植物的多重防御反应，并增强其对真菌病原体的抗性。该结果还表明，MdCERK1-2参与了苹果对病原真菌的防御反应。