Identification and characterisation of differentially expressed leaf proteins among <i>Vitis</i> species

<jats:title><jats:bold>Abstract</jats:bold></jats:title><jats:p>Grapes are commercially grown worldwide for fresh fruit and wine. They are mainly classified into bunch and muscadine grapes. These species differ in their sugar content and composition, photosynthetic efficiency and tolerance to abiotic and biotic stresses. Grape berry relies on carbohydrates produced during photosynthesis to support its development and composition. In view of the unique physiology and genetic make‐up of muscadine grape, a proteomics study was performed to increase our knowledge of <jats:italic>Vitis</jats:italic> leaf proteome in order to improve enological and disease tolerance characteristics of grape species. A high throughput two‐dimensional gel electrophoresis (2‐<jats:styled-content style="fixed-case">DE</jats:styled-content>) was conducted on muscadine, bunch and hybrid bunch leaf proteins. The differentially expressed proteins were excised from 2‐<jats:styled-content style="fixed-case">DE</jats:styled-content> gels, subjected to in‐gel trypsin digestion, and analysed in <jats:styled-content style="fixed-case">MALDI</jats:styled-content>/<jats:styled-content style="fixed-case">TOF</jats:styled-content> mass spectrometer. The mass spectra were collected and protein identification was performed by searching against <jats:italic>Viridiplantae</jats:italic> database using <jats:styled-content style="fixed-case">M</jats:styled-content>atrix <jats:styled-content style="fixed-case">S</jats:styled-content>cience algorithm. Proteins were mapped to universal protein resource to study gene ontology. We have discovered >255 proteins with <jats:styled-content style="fixed-case">pIs</jats:styled-content> between 3.5 and 8.0 and molecular weight between 12 and 100 <jats:styled-content style="fixed-case">kDa</jats:styled-content> among the <jats:italic>Vitis</jats:italic> species. Comparative analysis of leaf proteome showed that 54 polypeptides varied qualitatively and quantitatively among the three <jats:italic>Vitis</jats:italic> species studied. Of these, seven proteins were unique to muscadine, two proteins were present in both muscadine and bunch, while 28 proteins were common to all the three species. Bioinformatic analysis of these proteins showed that they are involved in signal transduction pathway, transport of metabolites, energy metabolism, protein trafficking, photosynthesis and defence. We have also identified proteins unique to muscadine grape that are involved in defence and stress tolerance. In addition, photosynthesis‐related proteins were found to be more abundant in <jats:italic>Vitis vinifera</jats:italic> grape compared to other <jats:italic>Vitis</jats:italic> species.</jats:p>