Seed priming with hormones has been an efficient method for increasing seed vigor as well as seedling growth under stressful conditions. These responses have in the past been attributed to the activation of antioxidant systems in a range of crops. The results described in this work show that hormonal priming with methyl jasmonate, salicylic acid or CEPA (chloroethylphosphonic acid), an ethylene (ET) releaser, does not induce the antioxidant activity of superoxide dismutase, catalase, ascorbate peroxidase or glutathione reductase in maize seedlings subjected to salt stress. The enhanced biomass of maize seedlings under salt stress that was observed only from ET priming indicates that the stress tolerance in maize from ethylene priming is a fundamental process for stress tolerance acquisition, which is explained, however, by other biochemical mechanisms but not by changes in the antioxidant system.

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C-hordein in barley and ω-gliadins in wheat are members of the prolamins protein families. Prolamins are the major component of cereal storage proteins and composed of non-essential amino acids (AA) such as proline and glutamine therefore have low nutritional value. Using double stranded RNAi silencing technology directed towards C-hordein we obtained transgenic barley lines with up to 94.7% reduction in the levels of C-hordein protein relative to the parental line. The composition of the prolamin fraction of the barley parental line cv. Golden Promise was resolved using SDS-PAGE electrophoresis, the protein band were excised and the proteins identified by quadrupole-time-of-flight mass spectrometry. Subsequent SDS-PAGE separation and analysis of the prolamin fraction of the transgenic lines revealed a reduction in the amounts of C-hordeins and increases in the content of other hordein family members. Analysis of the AA composition of the transgenic lines showed that the level of essential amino acids increased with a concomitant reduction in proline and glutamine. Both the barley C-hordein and wheat ω-gliadin genes proved successful for RNAi-gene mediated suppression of barley C-hordein level. All transgenic lines that exhibited a reduction for C-hordein showed off-target effects: the lines exhibited increased level of B/γ-hordein while D-hordein level was reduced. Furthermore, the multicopy insertions correlated negatively with silencing.

No abstract