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ARS Home » Pacific West Area » Wenatchee, Washington » Physiology and Pathology of Tree Fruits Research » Research » Publications at this Location » Publication #334524
Title: Functional characterization of an apple (Malus x domestica) LysM domain receptor encoding gene for its role in defense response

Author
item ZHOU, ZHE - Chinese Academy Of Agricultural Sciences
item CONG, PEIHUA - Chinese Academy Of Agricultural Sciences
item TIAN, TY - Chinese Academy Of Agricultural Sciences
item Zhu, Yanmin

Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2018
Publication Date: 2/15/2018
Citation: Zhou, Z., Cong, P., Tian, T., Zhu, Y. 2018. Functional characterization of an apple (Malus x domestica) LysM domain receptor encoding gene for its role in defense response. Plant Science. 269:56-65.

Interpretive Summary: To combat pathogen infection, plants are equipped with a sophisticated immune system through co-evolution with their pathogens. A group of plant proteins with the name of “pattern recognition receptors” (PRRs) is an integral component of this immune system, which can detect the presence of pathogens and subsequently activate the defense responses. Previous studies have demonstrated the contribution of PRRs to plant disease resistances in model plant system such as Arabidopsis and rice. In this study, the functional identity and the roles in defense responses of a PPR encoding gene in a perennial tree crop of apple were studied using combined genomic, transcriptional and proteomic approaches. Our previous transcriptome analysis indicated that an apple gene MDP0000136494 was the only LysM containing protein (a well-studied group of PRR) encoding gene which was specifically up-regulated in P. ultimum infected apple root. Sequence analysis on its genomic structure, domain composition and transcriptional response to exogenous chitin treatment confirmed that MDP0000136494 is an ortholog of AtCERK1, and was therefore named as MdCERK1. Transcriptional analysis indicated that this gene is primarily functional in apple vegetative tissues of leaf and root, rather than flower, fruit and seed. It was shown that its transcript level was up-regulated by infection of two root pathogens, i.e. Pythium ultimum and Rhizoctonia solani. Using heterologous expressed (in E. coli cells) GST-MdCERK1 fusion protein, the ability to bind chitin molecules was demonstrated. Non-target proteomic approach was also employed to identify its putative in vivo interacting plant protein partners. These data support the conclusion that that MdCERK1 is a chitin binding receptor kinase functioning in apple vegetative tissues. The results from this study provide the foundation to further elucidate its role contributing to resistance traits among apple genotypes/accessions. And these knowledge bases can present novel opportunity for crop improvement.

Technical Abstract: Apple gene MDP0000136494 was identified as the only LysM containing protein encoding gene which was specifically up-regulated in P. ultimum infected apple root by a previous transcriptome analysis. In current study, the functional identity of MDP0000136494 was investigated using combined genomic, transcriptional and proteomic approaches. Sequence analysis on the genomic structure, domain composition and transcriptional response to exogenous chitin treatment confirmed that MDP0000136494 is an ortholog of AtCERK1, and was therefore named as MdCERK1. Tissue specific expression patterns indicated that MdCERK1 is primarily functional in vegetative tissues of leaf and root, rather than flower, fruit and seed of apple plant. The transcriptional regulation patterns in response to infection by two root pathogens, i.e. Pythium ultimum and Rhizoctonia solani, demonstrated that MdCERK1 is a functional pattern recognition receptor protein (PRR) in apple. The ability to bind chitin molecules was exhibited using purified GST-MdCERK1 fusion protein, which added biochemical evidences for its role as a chitin binding receptor. Non-target proteomic approach was also employed to identify its putative in vivo interacting plant protein partners, which suggest the existence of a functional receptor complex in plant cell. These data support the conclusion that that MdCERK1 is a chitin binding receptor kinase functioning in apple vegetative tissues, which plays an important role in defense activation in response to pathogen infection. These results set the foundation for future transgenic and biochemical characterization of its role as functional PRR, as well as its genotype/accession specific defense activation for the contribution to resistance trait in apple plants.