Protein changes in response to progressive water deficit in maize . Quantitative variation and polypeptide identification

Abstract

Three-week-old plants of two unrelated lines of maize (Zea mays L.) and their hybrid were submitted to progressive water stress for 10 d. Changes induced in leaf proteins were studied by two-dimensional electrophoresis and quantitatively analyzed using image analysis. Seventy-eight proteins out of a total of 413 showed a significant quantitative variation (increase or decrease), with 38 of them exhibiting a different expression in the two genotypes. Eleven proteins that increased by a factor of 1.3 to 5 in stressed plants and 8 proteins detected only in stressed plants were selected for internal amino acid microsequencing, and by similarity search 16 were found to be closely related to previously reported proteins. In addition to proteins already known to be involved in the response to water stress (e.g. RAB17 [Responsive to ABA]), several enzymes involved in basic metabolic cellular pathways such as glycolysis and the Krebs cycle (e.g. enolase and triose phosphate isomerase) were identified, as well as several others, including caffeate O-methyltransferase, the induction of which could be related to lignification.

Figure 1

Computer image of a silver-stained 2DE gel of leaf proteins from the hybrid Io × Lc subjected to water stress in a growth cabinet. Numbered spots correspond to proteins in which quantity was altered during water stress (increased or decreased). Arrows indicate sequenced proteins induced in both growing conditions (bold type) or only in the greenhouse (normal type). Boxes correspond to gel regions enlarged in Figure 2. Molecular masses (in kilodaltons) are indicated.

Figure 2

Examples of protein induction in leaves of the maize line Io in response to 10 d of water deprivation in a control plant (A–E) and in a stressed plant (F–I). Letters correspond to the boxes in Figure 1. All plants except that shown in I were grown in a growth cabinet. Peptides from spots 159 (A), 252 (B), 383 (B), 754 (C), 1133 (E), 137 (F), 714 (G), and 1306 (I) were microsequenced (see Table II).