1 Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET-UNT, and Instituto de Química Biológica "Dr. Bernabé Bloj", Facultad de Bioquímica, Química y Farmacia, UNT. Chacabuco 461, T4000ILI, San Miguel de Tucumán, Argentina.
2 Cátedra de Anatomía Vegetal, Facultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de Tucumán. Miguel Lillo 205, 4000, Tucumán, Argentina, and Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Catamarca. Av. Belgrano 300, 4700, San Fernando del Valle de Catamarca, Catamarca, Argentina; and.
Mol Plant Microbe Interact. 2018 Jan;31(1):46-60. doi: 10.1094/MPMI-05-17-0121-FI. Epub 2017 Aug 28.
The elicitor AsES (Acremonium strictum elicitor subtilisin) is a 34-kDa subtilisin-like protein secreted by the opportunistic fungus Acremonium strictum. AsES activates innate immunity and confers resistance against anthracnose and gray mold diseases in strawberry plants (Fragaria × ananassa Duch.) and the last disease also in Arabidopsis. In the present work, we show that, upon AsES recognition, a cascade of defense responses is activated, including: calcium influx, biphasic oxidative burst (O and HO), hypersensitive cell-death response (HR), accumulation of autofluorescent compounds, cell-wall reinforcement with callose and lignin deposition, salicylic acid accumulation, and expression of defense-related genes, such as FaPR1, FaPG1, FaMYB30, FaRBOH-D, FaRBOH-F, FaCHI23, and FaFLS. All these responses occurred following a spatial and temporal program, first induced in infiltrated leaflets (local acquired resistance), spreading out to untreated lateral leaflets, and later, to distal leaves (systemic acquired resistance). After AsES treatment, macro-HR and macro-oxidative bursts were localized in infiltrated leaflets, while micro-HRs and microbursts occurred later in untreated leaves, being confined to a single cell or a cluster of a few epidermal cells that differentiated from the surrounding ones. The differentiated cells initiated a time-dependent series of physiological and anatomical changes, evolving to idioblasts accumulating HO and autofluorescent compounds that blast, delivering its content into surrounding cells. This kind of systemic cell-death process in plants is described for the first time in response to a single elicitor. All data presented in this study suggest that AsES has the potential to activate a wide spectrum of biochemical and molecular defense responses in F. ananassa that may explain the induced protection toward pathogens of opposite lifestyle, like hemibiotrophic and necrotrophic fungi.
激发子 AsES（细弱拟青霉激发子蛋白酶）是一种由机会性真菌细弱拟青霉分泌的 34kDa 类枯草杆菌蛋白酶。AsES 激活先天免疫，并赋予草莓植物（Fragaria×ananassa Duch.）对炭疽病和灰霉病的抗性，以及对拟南芥的后一种疾病的抗性。在本工作中，我们表明，在 AsES 识别后，会激活一系列防御反应，包括：钙离子内流、双相氧化爆发（O 和 HO）、过敏细胞死亡反应（HR）、积累自发荧光化合物、细胞壁用胼胝质加固和木质素沉积、水杨酸积累以及防御相关基因的表达，如 FaPR1、FaPG1、FaMYB30、FaRBOH-D、FaRBOH-F、FaCHI23 和 FaFLS。所有这些反应都遵循时空程序发生，首先在浸润的小叶中诱导（局部获得抗性），扩散到未处理的侧小叶，然后扩散到远端叶片（系统获得抗性）。在 AsES 处理后，宏观 HR 和宏观氧化爆发定位于浸润的小叶中，而微观 HR 和微爆发稍后发生在未处理的叶片中，局限于单个细胞或少数几个从周围细胞分化而来的表皮细胞。分化细胞启动了一系列与时间相关的生理和解剖变化，演变为积累 HO 和自发荧光化合物的异形细胞，这些化合物爆炸，将其内容物释放到周围细胞中。这种植物的系统性细胞死亡过程是首次在响应单个激发子时描述的。本研究中提出的所有数据表明，AsES 有可能激活草莓植物中广泛的生化和分子防御反应，这可以解释其对具有不同生活方式的病原体的诱导保护作用，如半活体和坏死真菌。
