ORIGINAL RESEARCH published: 26 July 2016 doi: 10.3389/fpls.2016.01108 Edited by: Qingsong Lin, National University of Singapore, Singapore Reviewed by: Ján A. Miernyk, University of Missouri, USA Uener Kolukisaoglu, University of Tübingen, Germany *Correspondence: Maciej Stobiecki mackis@ibch.poznan.pl Pawel Bednarek bednarek@ibch.poznan.pl † These authors have contributed equally to this work and should be considered co-first authors. Specialty section: This article was submitted to Plant Physiology, a section of the journal Frontiers in Plant Science Received: 06 May 2016 Accepted: 12 July 2016 Published: 26 July 2016 Citation: Chmielewska K, Rodziewicz P, Swarcewicz B, Sawikowska A, Krajewski P, Marczak L, Ciesiolka D, Kuczy ´ nska A, Mikolajczak K, Ogrodowicz P, Krystkowiak K, Surma M, Adamski T, Bednarek P and Stobiecki M (2016) Analysis of Drought-Induced Proteomic and Metabolomic Changes in Barley (Hordeum vulgare L.) Leaves and Roots Unravels Some Aspects of Biochemical Mechanisms Involved in Drought Tolerance. Front. Plant Sci. 7:1108. doi: 10.3389/fpls.2016.01108 Analysis of Drought-Induced Proteomic and Metabolomic Changes in Barley (Hordeum vulgare L.) Leaves and Roots Unravels Some Aspects of Biochemical Mechanisms Involved in Drought Tolerance Klaudia Chmielewska 1† , Pawel Rodziewicz 1† , Barbara Swarcewicz 1† , Aneta Sawikowska 2† , Pawel Krajewski 2 , Lukasz Marczak 1 , Danuta Ciesiolka 1 , Anetta Kuczy ´ nska 2 , Krzysztof Mikolajczak 2 , Piotr Ogrodowicz 2 , Karolina Krystkowiak 2 , Maria Surma 2 , Tadeusz Adamski 2 , Pawel Bednarek 1 * and Maciej Stobiecki 1 * 1 Institute of Bioorganic Chemistry – Polish Academy of Sciences, Pozna ´ n, Poland, 2 Institute of Plant Genetics – Polish Academy of Sciences, Pozna ´ n, Poland In this study, proteomic and metabolomic changes in leaves and roots of two barley (Hordeum vulgare L.) genotypes, with contrasting drought tolerance, subjected to water deficit were investigated. Our two-dimensional electrophoresis (2D-PAGE) combined with matrix-assisted laser desorption time of flight mass spectrometry (MALDI-TOF and MALDI-TOF/TOF) analyses revealed 121 drought-responsive proteins in leaves and 182 in roots of both genotypes. Many of the identified drought-responsive proteins were associated with processes that are typically severely affected during water deficit, including photosynthesis and carbon metabolism. However, the highest number of identified leaf and root proteins represented general defense mechanisms. In addition, changes in the accumulation of proteins that represent processes formerly unassociated with drought response, e.g., phenylpropanoid metabolism, were also identified. Our tandem gas chromatography – time of flight mass spectrometry (GC/MS TOF) analyses revealed approximately 100 drought-affected low molecular weight compounds representing various metabolite types with amino acids being the most affected metabolite class. We compared the results from proteomic and metabolomic analyses to search for existing relationship between these two levels of molecular organization. We also uncovered organ specificity of the observed changes and revealed differences in the response to water deficit of drought susceptible and tolerant barley lines. Particularly, our results indicated that several of identified proteins and metabolites whose accumulation levels were increased with drought in the analyzed susceptible barley variety revealed elevated constitutive accumulation levels in the drought-resistant line. This may suggest that constitutive biochemical predisposition represents a better drought tolerance mechanism than inducible responses. Keywords: abiotic stress, barley, drought stress, mass spectrometry, metabolome, proteome Frontiers in Plant Science | www.frontiersin.org 1 July 2016 | Volume 7 | Article 1108