Proteomic and morphological analysis of early stages of wheat grain development.

The identification of 249 proteins in the first 2 wks of wheat grain development enabled the chronological description of the early processes of grain formation. Cell division involved expression of the enzymes and proteins of the cytoskeleton and structure, DNA repair and replication enzymes and cellular metabolism enzymes (synthesis of amino acids, cell wall initiation, carbon fixation and energy production, cofactors and vitamins) with a peak expression at 125 degrees C day (degrees day after anthesis). After the first synthesis of amino acids, protein transport mechanisms, translation signals, sugar metabolism (polymerization of protein) and stress/defence proteins were activated with stable expression between 150 and 280 degrees C day. Proteins responsible for folding and degradation, including different subunits of proteasome, were highly expressed at 195 degrees C day. Proteins associated with starch granules (GBSS type 1) were present at the beginning of grain formation and increased regularly up to 280 degrees C day. Heat shock proteins (HSP70, 80, 90) were expressed throughout the early grain development stages.