A two-dimensional proteome map of maize endosperm q Val  erie M echin a,b , Thierry Balliau a,c , Sophie Ch^ ateau-Joubert d , Marl  ene Davanture c , Olivier Langella a,c , Luc N egroni a,c , Jean-Louis Prioul d , Claudine Th evenot d , Michel Zivy a , Catherine Damerval a, * a INRA/INA-PG/UPS/CNRS UMR8120, UMR de G en etique V eg etale, Ferme du Moulon, 91190 Gif-sur-Yvette, France b Unit e de Chimie Biologique UMR 206, INRA/INA-PG, Institut National Agronomique, 78850 Thiverval-Grignon, France c IFR 87 La Plante et son Environnement, Plate-forme de Prot eomique du Moulon, UMR de G en etique V eg etale, Ferme du Moulon, 91190 Gif-sur-Yvette, France d Laboratoire Structure et M etabolisme des Plantes, Institut de Biotechnologie des Plantes (CNRS UMR 8618), B^ atiment 630, Universit e Paris-Sud, 91405 Orsay Cedex, France Received 12 January 2004; received in revised form 27 April 2004 Available online 25 June 2004 Abstract We have established a proteome reference map for maize (Zea mays L.) endosperm by means of two-dimensional gel electro- phoresis and protein identification with LC–MS/MS analysis. This investigation focussed on proteins in major spots in a 4–7 pI range and 10–100 kDa M r range. Among the 632 protein spots processed, 496 were identified by matching against the NCBInr and ZMtuc-tus databases (using the SEQUEST software). Forty-two per cent of the proteins were identified against maize sequences, 23% against rice sequences and 21% against Arabidopsis sequences. Identified proteins were not only cytoplasmic but also nuclear, mitochondrial or amyloplastic. Metabolic processes, protein destination, protein synthesis, cell rescue, defense, cell death and ageing are the most abundant functional categories, comprising almost half of the 632 proteins analyzed in our study. This proteome map constitutes a powerful tool for physiological studies and is the first step for investigating the maize endosperm development. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Zea mays L.; Poaceae; Maize; 2D PAGE; LC–MS/MS; Endosperm proteins; 2D map 1. Introduction During maize seed development, several physiological steps involving complex and inter-related processes can be recognized. For the first 3 days after pollination, free nuclear divisions followed by cellularisation of the coe- nocyte occur. The formation of cell walls begins at 4 days after pollination when the endosperm contains several thousand cells. From 4 to 10 days after polli- nation, cell division and differentiation take place, then storage compounds are synthesized from 12 days after pollination to the maturity. During this period, the en- dosperm accumulates large amounts of starch and storage proteins. At around 25 days after pollination, the relative water content of the endosperm begins to decrease and the dry down process initiates. Whilst morphological steps of this development are well known, until now the underlying physiological and molecular mechanisms are largely unknown. One way to appraise these complex processes is to study the prote- ome of the endosperm at several key stages along de- velopment, which would give insight to the functional gene products and how their expression is modulated. Most proteomic studies still rely on two-dimensional (2D) electrophoresis, which uses two independent q Supplementary data associated with this article can be found at doi:10.1016/j.phytochem.2004.04.035. Abbreviations: ACN, acetonitrile; DTT, dithiothreitol; EST, ex- pressed sequence tag; HPLC, high-pressure liquid chromatography; IT, ion trap; MS, mass spectrometry; PDA, piperazine diacrylyl; SB3-10, N-decyl-N,N-dimethyl-3-ammonio-1-propane-sulfonate; SDS, sodium dodecyl sulfate; TCA, tricarboxylic acid cycle; TCEP, tris(2- carboxyethyl)phosphine; TFA, trifluoroacetic acid. * Corresponding author. Tel.: +33-1-69-33-2366; fax: +33-1-69-33- 2340. E-mail address: damerval@moulon.inra.fr (C. Damerval). 0031-9422/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.phytochem.2004.04.035 Phytochemistry 65 (2004) 1609–1618 PHYTOCHEMISTRY www.elsevier.com/locate/phytochem