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

Abstract

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.

The fifth leaf and spike organs of barley (Hordeum vulgare L.) display different physiological and metabolic responses to drought stress

“…Transcriptome studies have shown that genes for heat shock proteins (chaperones), late-embryogenesis abundant (LEA) proteins, osmolyte biosynthesis, ROS scavenging, signal transduction, defense, and others are up-regulated in response to drought [37–41]. These changes at the transcription level also increase accumulation of proteins and metabolites involved in drought resistance [42–45]. …”

BarleyNet: A Network-Based Functional Omics Analysis Server for Cultivated Barley, Hordeum vulgare L.

“…We thus evaluated BarleyNet in the prediction of complex traits based on the connectivity within a group of genes involved in the same traits. For this, we compiled genes for complex traits from drought-induced proteomic profiles of barley (Chmielewska et al, 2016). This study identified differentially accumulated proteins in the leaves and roots of two barley cultivars, Maresi and Cam/B1/CI (referred to as CAM), after 10 days of drought.…”

Covariance regularization for metabolomic data on the drought resistance of barley

“…The following nine spring barley genotypes were used: the European varieties Georgia, Maresi, Lubuski, Sebastian and Stratus; Morex, bred in the USA; and Cam/B1/CI 08887//Cl 0576, Harmal, and Maris Dingo/Deir Alla 106, being lines bred in Syria. Barley plants were cultivated under partially controlled greenhouse conditions; see Chmielewska et al (2016) for more details. The primary metabolites were recognized by gas chromatography coupled with mass spectrometry (GC-MS), which is the most widely applied technique playing an important role in the identification and quantification of chemical compounds in analyzed samples.…”