Centro de Biotecnologia y Genomica de Plantas (CBGP, UPM-INIA), Universidad Politecnica de Madrid (UPM) - Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Madrid, Pozuelo de Alarcon, Spain.
Departamento de Biotecnologia-Biologia Vegetal, Escuela Tecnica Superior de Ingenieria Agronomica, Alimentaria y de Biosistemas, UPM, 28040, Madrid, Spain.
BMC Plant Biol. 2018 Dec 6;18(1):337. doi: 10.1186/s12870-018-1560-6.
Phytocystatins (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.
The 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.
These 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.
植物半胱氨酸蛋白酶抑制剂（PhyCys）作为参与各种生理过程的半胱氨酸蛋白酶（CysProt）的内源性调节剂。此外，PhyCys 还参与植物对干旱或黑暗等非生物胁迫的反应，并已被用作抵抗不同害虫和病原体的有效分子。大麦 PhyCys-CysProt 系统被认为是蛋白酶抑制剂调节蛋白周转的模型。先前已经鉴定和表征了 13 种大麦半胱氨酸蛋白酶抑制剂（HvCPI-1 到 HvCPI-13）。其中，HvCPI-2 已被证明在植物对病原体和害虫的反应以及对干旱的反应中具有重要作用。
本研究探讨了这种大麦 PhyCys 在应对生物和非生物胁迫中的多种作用，重点研究了沉默该基因的影响。HvIcy-2 沉默系对植物病原菌稻瘟病菌和光照剥夺处理表现出不同的反应。真菌胁迫诱导 HvIcy-2 的表达与沉默 HvIcy-2 植物的易感性增加相关。相比之下，沉默 HvIcy-2 植物中 HvIcy-2 的表达降低以及组织蛋白酶-L 和 -B 样活性的降低，在对光照剥夺的反应中并没有伴随与对照植物明显的表型差异。
这些结果突出了 PhyCys 在应对不同外部提示的反应中的特异性，以及导致对特定胁迫产生反应的调控事件的复杂性。这些应激反应的调控机制似乎集中在维持 CysProt 和 PhyCys 水平的平衡上，这对于调节生物或非生物胁迫诱导的生理过程至关重要。
