Mitogen activated protein kinases (MAPKs) integrate elicitor perception with both early and late responses associated with plant defense and innate immunity. Much of the existing knowledge on the role of plant MAPKs in defense mechanisms against microbes stems from extensive research in the model plant Arabidopsis thaliana. In the present study, we investigated the involvement of barley (Hordeum vulgare) MPK3 in response to flagellin peptide flg22, a well-known bacterial elicitor. Using differential proteomic analysis we show that TALEN-induced MPK3 knock-out lines of barley (HvMPK3 KO) exhibit constitutive downregulation of defense related proteins such as PR proteins belonging to thaumatin family and chitinases. Further analyses showed that the same protein families were less prone to flg22 elicitation in HvMPK3 KO plants compared to wild types. These results were supported and validated by chitinase activity analyses and immunoblotting for HSP70. In addition, differential proteomes correlated with root hair phenotypes and suggested tolerance of HvMPK3 KO lines to flg22. In conclusion, our study points to the specific role of HvMPK3 in molecular and root hair phenotypic responses of barley to flg22.

Department of Cell Biology Centre of the Region Haná for Biotechnological and Agricultural Research Faculty of Science Palacký University Olomouc Olomouc Czechia

Institute for Genomics Biocomputing and Biotechnology Mississippi Agricultural and Forestry Experiment Station Mississippi State University Starkville MS United States

Laboratory of Growth Regulators Palacký University and Institute of Experimental Botany Czech Academy of Sciences Olomouc Czechia

Laboratory of Transgenic Models of Diseases Institute of Molecular Genetics of the CAS Vestec Czechia

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