Differential response of silencing HvIcy2 barley plants under biotic and abiotic stresses

The knowlegde on the multiple role of cysteine-proteases and their inhibitors, phytocystatins, in response to stress is still limited. Our goal was to analyse how the silencing of the HvIcy-2 cystatin gene in barley plants may alter responses to stress. HvIcy-2 silencing lines behave differentially against the phytopathogenic fungus Magnaporthe oryzae and a light deprivation treatment. The induced expression of HvIcy-2 gene by the fungal stress correlated to a higher susceptibility of silencing HvIcy-2 plants. In contrast, a reduction in the expression of HvIcy-2 and in the cysteine-protease activities in the silencing HvIcy-2 plants was not accompanied by apparent phenotypical differences with control plants in response to light deprivation. These results highlight the specificity of phytocystatins in the responses to diverse external prompts as well as the complexity of the regulatory events leading to the response to a particular stress. The mechanism of regulation of these stress responses seems to be focused in maintaining the balance of cysteine-proteases and cystatin levels, which is crucial for the modulation of physiological processes induced by biotic or abiotic stresses.