MdPR4, a pathogenesis-related protein in apple, is involved in chitin recognition and resistance response to apple replant disease pathogens

Authors: ZHOU, ZHE - Chinese Academy Of Agricultural Sciences; Zhu, Yanmin; YI, TIAN - Hebei Academy Of Agriculture; JIA-LONG, YAO - Chinese Academy Of Agricultural Sciences; SHUXUN, BIAN - Chinese Academy Of Agricultural Sciences; HENGTAO, ZHANG - Chinese Academy Of Agricultural Sciences; RUIPING, ZHANG - Chinese Academy Of Agricultural Sciences; QIMING, GAO - Chinese Academy Of Agricultural Sciences; ZHENZHEN, LIU - Chinese Academy Of Agricultural Sciences; ZHENLI, YAN - Chinese Academy Of Agricultural Sciences

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2021
Publication Date: 2/9/2021
Citation: Zhou, Z., Zhu, Y., Yi, T., Jia-Long, Y., Shuxun, B., Hengtao, Z., Ruiping, Z., Qiming, G., Zhenzhen, L., Zhenli, Y. 2021. MdPR4, a pathogenesis-related protein in apple, is involved in chitin recognition and resistance response to apple replant disease pathogens. Journal of Plant Physiology. 260.Article 153390. https://doi.org/10.1016/j.jplph.2021.153390.
DOI: https://doi.org/10.1016/j.jplph.2021.153390

Interpretive Summary: Plants are prone to diseases caused by pathogens just as humans are. Plants can recognize they are under attack by pathogens and, just like us, respond via an immune system that protects them from disease. Apple trees can have a disease in their roots that can limit tree growth or cause the tree to die. Understanding how this process works may help to develop new apple rootstocks that are resistant to disease. This study discovered a gene that may be part of the apple rootstock immune system that helps the tree to avoid disease. The results may enable development of new rootstocks that protect the tree from disease without the use of anti-pathogen chemicals.

Technical Abstract: It is of great importance to understand the resistance mechanisms in apple root to replant pathogen for rapid breeding cycles and maximized exploitation of disease resistance traits for managing ARD. Currently, there is limited knowledge regarding the functions of specific genes to apple root resistance traits. In this study, the molecular, biochemical and genetic approaches allowed an in-depth understanding of the role of MdPR4 in apple root during defense response. MdPR4 encoding gene showed upregulation after ARD pathogen inoculation in our previous transcriptome data. Tissue specific expression patterns indicated that MdPR4 is primarily functional in apple vegetative tissues rather than reproductive tissues. Subcellular localization analyses also revealed that MdPR4 is localized to the plasma membrane. The molecular mechanisms by which MdPR4 affect fungi were elucidated by molecular docking. Recombinant MdPR4 protein expressed in E.coli exhibited chitin binding ability, which added biochemical evidence for its role in chitin mediated immune responses. Transgenic apple callus, which overexpressed MdPR4 showed increased resistance to ARD-related Fusarium sp. by hindering the pathogen growth. These data support the conclusion that MdPR4 is a membrane-localized chitin-binding protein functioning in apple vegetative tissues, which may play an important role in defense activation in response to ARD pathogen infection.