Figure 1.
The gas exchange and water use characteristics of the leaves of drought-stressed maize genotypes.
The net photosynthetic rate (PN) (A), intercellular CO2 concentration (ci) (B), net transpiration rate (E) (C), stomatal conductance (gS) (D), water use efficiency (WUE) (E) and relative water content (RWC) (F) in the leaves of two maize genotypes (2023 and CE704) that were subjected to 6 days of drought (solid bars) or normally watered (hatched bars). The means ± SD (n = 18) are shown. The letters a-c denote the statistical significance (as determined by the Tukey-Kramer test) of the differences between genotypes/water treatments (only those marked with different letters differ significantly at p≤0.05).
Figure 2.
The morphology and biomass characteristics of drought-stressed maize genotypes.
The dry mass of the shoot (DMS) (A), dry mass of the roots (DMR) (B), specific weight of the 4th leaf (SLW) (C) and plant height (D) of two maize genotypes (2023 and CE704) subjected to 6 days of drought (solid bars) or normally watered (hatched bars). The means ± SD (n = 20) are shown. The letters a-c denote the statistical significance (as determined by the Tukey-Kramer test) of the differences between genotypes/water treatments (only those marked with different letters differ significantly at p≤0.05).
Figure 3.
The activities of antioxidant enzymes in the leaves of drought-stressed maize genotypes.
The activities of ascorbate peroxidase (APX) (A), glutathione reductase (GR) (B), superoxide dismutase (SOD) (C) and catalase (CAT) (D) in the leaves of two maize genotypes (2023 and CE704) subjected to 6 days of drought (solid bars) or normally watered (hatched bars). The means ± SD (n = 8) are shown. The letters a-b denote the statistical significance (as determined by the Tukey-Kramer test) of the differences between genotypes/water treatments (only those marked with different letters differ significantly at p≤0.05).
Figure 4.
The functional classification of differentially expressed drought-related proteins from maize leaves.
The number of proteins identified by the iTRAQ method in two maize genotypes (2023 and CE704) with up-regulated (A) or down-regulated (B) levels is shown; only those proteins whose levels changed due to drought in at least one genotype by at least twofold were included. ET: proteins of the photosynthetic electron-transport chain and chlorophyll synthesis; SM: proteins participating in photosynthetic carbon fixation and saccharide metabolism; MT: membrane proteins participating in transport; LM: proteins participating in lipid metabolism; AM: proteins participating in amino acid metabolism; DX: detoxification proteins; ST: stress proteins; DH: dehydrins; CP: chaperones; SG: proteins involved in cell signaling; PT: proteases and their inhibitors; GE: proteins participating in gene expression and its regulation; MS: miscellaneous proteins.
Figure 5.
The functional classification of differentially expressed proteins from maize leaves with genotype-dependent contrasting responses to drought.
The number of proteins identified by the iTRAQ method that were up-regulated in one genotype and down-regulated in the other genotype or vice versa is shown in panel (A); the number of proteins belonging to this category with different levels in control plants of both genotypes is shown in panel (B). Only proteins whose levels changed differentially in the two genotypes by at least twofold were included. 2023> CE704: up-regulation of protein levels in the 2023 genotype and down-regulation in the CE704 genotype (A) or higher level in control plants of the CE704 genotype compared with the 2023 genotype (B); CE704>2023: up-regulation of protein levels in the CE704 genotype and down-regulation in the 2023 genotype (A) or higher level in control plants of the 2023 genotype compared with the CE704 genotype (B); ET: proteins of the photosynthetic electron-transport chain and chlorophyll synthesis; SM: proteins participating in photosynthetic carbon fixation and saccharide metabolism; MT: membrane proteins participating in transport; LM: proteins participating in lipid metabolism; AM: proteins participating in amino acid metabolism; DX: detoxification proteins; ST: stress proteins; DH: dehydrins; CP: chaperones; SG: proteins involved in cell signaling; PT: proteases and their inhibitors; GE: proteins participating in gene expression and its regulation; MS: miscellaneous proteins.
Table 1.
Five most up-regulated and down-regulated proteins in drought-stressed maize plants of 2023 and CE704 genotypes, as revealed by the iTRAQ analysis.
Table 2.
Five proteins with the strongest contrast in the response to drought between 2023 and CE704 maize genotypes.
Figure 6.
The 2D gels showing the leaf proteomes of drought-stressed and control plants of two maize genotypes.
S: drought-stressed; C: control; 2023: sensitive genotype; CE704: tolerant genotype. Only selected regions of the gels are shown; the frames mark the differences in the representation of two isoforms of the heat-shock protein HSP26 (spots nos. 4 and 5) in the drought-stressed plants of both genotypes. The protein spots that are differentially represented between genotypes and water treatments are marked by arrows and the respective numbers (1–11; N … unidentified protein) refer to the notation used in Table 3.
Table 3.
The differences in leaf proteins observed either between the genotypes or between control (C) and drought-stressed (S) plants of 2023 and CE704 maize genotypes, as evaluated by the 2D-electrophoresis method.
Figure 7.
Phenotypic representation of drought-stressed and control plants of two maize genotypes.
2023: sensitive genotype; CE704: tolerant genotype.