title: Proteins associated with cork formation in Quercus suber L. stem tissues.
abstract: Cork (phellem) formation in Quercus suber stem was studied by proteomic analysis of young shoots of increasing age (Y0, Y1 and Y4) and recently-formed phellem (Y8Ph) and xylem (Y8X) from an 8-year-old branch. In this study 99 proteins were identified, 45 excised from Y8X and 54 from Y8Ph. These ones, specifically associated with phellem, are of "carbohydrate metabolism" (28%), "defence" (22%), "protein folding, stability and degradation" (19%), "regulation/signalling" (11%), "secondary metabolism" (9%), "energy metabolism" (6%), and "membrane transport" (2%). The identification in phellem of galactosidases, xylosidases, apiose/xylose synthase, laccases and diphenol oxidases suggests intense cell wall reorganization, possibly with participation of hemicellulose/pectin biosynthesis and phenol oxidation. The identification of proteasome subunits, heat shock proteins, cyclophylin, subtilisin-like proteases, 14-3-3 proteins, Rab2 protein and enzymes interacting with nucleosides/nucleic acids gives additional evidence for cellular reorganization, involving cellular secretion, protein turnover regulation and active control processes. The high involvement in phellem of defence proteins (thioredoxin-dependent peroxidase, glutathione-S-transferase, SGT1 protein, cystatin, and chitinases) suggests a strong need for cell protection from the intense stressful events occurring in active phellem, namely, desiccation, pests/disease protection, detoxification and cell death. Identically, highly enhanced defence functions were previously reported for potato periderm formation.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, EAN, 2780-157 Oeiras, Portugal. ricardo@itqb.unl.pt
authors.forename: Cândido P P
authors.initials: CP
authors.lastname: Ricardo
authors.forename: Isabel
authors.initials: I
authors.lastname: Martins
authors.forename: Rita
authors.initials: R
authors.lastname: Francisco
authors.forename: Kjell
authors.initials: K
authors.lastname: Sergeant
authors.forename: Carla
authors.initials: C
authors.lastname: Pinheiro
authors.forename: Alexandre
authors.initials: A
authors.lastname: Campos
authors.forename: Jenny
authors.initials: J
authors.lastname: Renaut
authors.forename: Pedro
authors.initials: P
authors.lastname: Fevereiro
mesh_terms: D015180:Electrophoresis, Gel, Two-Dimensional; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018547:Plant Stems / Q000378:metabolism*; D040901:Proteomics; D029963:Quercus / Q000378:metabolism*
chemical_list: D010940:Plant Proteins