Pretreatment with 0.5 mM salicylic acid (SA) for 3 days significantly enhanced the growth and tolerance to subsequent drought stress (PEG-6000, 15%) in wheat seedlings, manifesting as increased shoot and root dry weights, and decreased lipid peroxidation. Total proteins from wheat leaves exposed to (i) 0.5 mM SA pretreatment, (ii) drought stress, and (iii) 0.5 mM SA treatment plus drought-stress treatments were analyzed using a proteomics method. Eighty-two stress-responsive protein spots showed significant changes, of which 76 were successfully identified by MALDI-TOF-TOF. Analysis of protein expression patterns revealed that proteins associated with signal transduction, stress defense, photosynthesis, carbohydrate metabolism, protein metabolism, and energy production could by involved in SA-induced growth and drought tolerance in wheat seedlings. Furthermore, the SA-responsive protein interaction network revealed 35 key proteins, suggesting that these proteins are critical for SA-induced tolerance.

Treatment with 0.5 mM salicylic acid (SA) significantly alleviated growth inhibition induced by drought in wheat seedlings, manifested by less decreassed fresh mass, dry mass, plant height, root length, and less increased lipid peroxidation. Under drought stress, SA significantly increased the content of ascorbate (ASA) and glutathione (GSH). We determined the full-length cDNA sequences of genes encoding the glutathione-S-transferase 1 (GST1) and 2 (GST2) and we also measured the transcription of eight genes related to ASA-GSH cycle. The results indicated that exogenous SA significantly enhanced the transcription of GST1, GST2, glutathione reductase (GR), and monodehydroascorbate reductase (MDHAR) genes during almost the entire drought period, but only increased those of dehydroascorbate reductase (DHAR) at 12 h, glutathione peroxidase (GPX1) at 48 h, phospholipid hydroperoxide glutathione peroxidase (GPX2) at 12 and 24 h, and glutathione synthetase (GSHS) at 12, 24, and 48 h. This implies that SA alleviates the detrimental effects of drought stress on wheat seedling growth by influencing the ASA-GSH cycle.

Proteomic studies were performed to identify the protein species involved in copper (Cu) stress responses in common wheat. Two-week-old wheat seedlings were exposed to 100 μM CuSO4 treatment for 3 days. Growth of shoots and roots was markedly inhibited and lipid peroxidation was greatly increased. Cu was readily absorbed by wheat seedlings, with greater Cu contents in roots than in leaves. Using 2-DE method, 98 protein spots showed significantly enhanced or reduced abundance, of which 93 were successfully identified. Of these identified protein species, 49 and 44 were found in roots and leaves, respectively. Abundance of most of identified protein species, which function in signal transduction, stress defense, and energy production, was significantly enhanced, while that of many protein species involved in carbohydrate metabolism, protein metabolism, and photosynthesis was severely reduced. The Cu-responsive protein interaction network revealed 36 key proteins, most of which may be regulated by abscisic acid (ABA), ethylene, jasmonic acid (JA), and so on. Exogenous JA application showed a protective effect against Cu stress and significantly increased transcripts of the glutathione S-transferase (GST) gene. This study provides insight into the molecular mechanisms of Cu responses in higher plants.

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