Abstract
BackgroundPhytocystatins (PhyCys) act as endogenous regulators of cysteine proteases (CysProt) involved in various physiological processes. Besides, PhyCys are involved in plant reactions to abiotic stresses like drought or darkness and have been used as effective molecules against different pests and pathogens. The barley PhyCys-CysProt system is considered a model of protease-inhibitor regulation of protein turnover. Thirteen barley cystatins (HvCPI-1 to HvCPI-13) have been previously identified and characterized. Among them HvCPI-2 has been shown to have a relevant role in plant responses to pathogens and pests, as well as in the plant response to drought.ResultsThe present work explores the multiple role of this barley PhyCys in response to both, biotic and abiotic stresses, focusing on the impact of silencing this gene. HvIcy-2 silencing lines behave differentially against the phytopathogenic fungus Magnaporthe oryzae and a light deprivation treatment. The induced expression of HvIcy-2 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 cathepsin-L and -B like activities in the silencing HvIcy-2 plants was not accompanied by apparent phenotypical differences with control plants in response to light deprivation.ConclusionThese results highlight the specificity of PhyCys 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 CysProt and PhyCys levels, which is crucial for the modulation of physiological processes induced by biotic or abiotic stresses.
Highlights
Phytocystatins (PhyCys) act as endogenous regulators of cysteine proteases (CysProt) involved in various physiological processes
Among plant protease inhibitors, the cysteine protease (CysProt) inhibitors called phytocystatins (PhyCys) have been largely studied since they participate in numerous physiological processes
Expression of HvIcy-2 is modified in barley leaves during the response to elicitors and M. oryzae treatments The in vitro inhibition of the fungal growth of some phytopathogenic fungus like M. oryzae points to a relevant role for HvCPI-2 in plant responses to pathogens, [47]
Summary
Phytocystatins (PhyCys) act as endogenous regulators of cysteine proteases (CysProt) involved in various physiological processes. PhyCys are involved in plant reactions to abiotic stresses like drought or darkness and have been used as effective molecules against different pests and pathogens. The cysteine protease (CysProt) inhibitors called phytocystatins (PhyCys) have been largely studied since they participate in numerous physiological processes. PhyCys act as endogenous regulators of protein turnover in many physiological processes, such as plant growth and development, ripening, accumulation and mobilization of Velasco-Arroyo et al BMC Plant Biology (2018) 18:337. Maize plants silencing the cystatin-9 gene had a reduced infection by Ustilago maydis, indicating that this PhyCys suppresses host immunity by inhibition of apoplastic cysteine proteases [32]. PhyCys may act as stabilizing fusion partners for recombinant protein production in plants [41,42,43]
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