Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET-UNT, and Instituto de Química Biológica "Dr. Bernabé Bloj", Facultad de Bioquímica, Química y Farmacia, UNT, San Miguel de Tucumán, Argentina.
The Sainsbury Laboratory, University of East Anglia, Norwich Research Park, Norwich, United Kingdom.
Mol Plant Pathol. 2020 Feb;21(2):147-159. doi: 10.1111/mpp.12881. Epub 2019 Nov 26.
Acremonium strictum elicitor subtilisin (AsES) is a 34-kDa serine-protease secreted by the strawberry fungal pathogen A. strictum. On AsES perception, a set of defence reactions is induced, both locally and systemically, in a wide variety of plant species and against pathogens of alternative lifestyles. However, it is not clear whether AsES proteolytic activity is required for triggering a defence response or if the protein itself acts as an elicitor. To investigate the necessity of the protease activity to activate the defence response, AsES coding sequences of the wild-type gene and a mutant on the active site (S226A) were cloned and expressed in Escherichia coli. Our data show that pretreatment of Arabidopsis plants with inactive proteins, i.e. inhibited with phenylmethylsulphonyl fluoride (PMSF) and mutant, resulted in an increased systemic resistance to Botrytis cinerea and expression of defence-related genes in a temporal manner that mimics the effect already reported for the native AsES protein. The data presented in this study indicate that the defence-eliciting property exhibited by AsES is not associated with its proteolytic activity. Moreover, the enhanced expression of some immune marker genes, seedling growth inhibition and the involvement of the co-receptor BAK1 observed in plants treated with AsES suggests that AsES is being recognized as a pathogen-associated molecular pattern by a leucine-rich repeat receptor. The understanding of the mechanism of action of AsES will contribute to the development of new breeding strategies to confer durable resistance in plants.
严格棘孢木霉激发子丝氨酸蛋白酶（AsES）是一种由草莓真菌病原体棘孢木霉分泌的 34kDa 丝氨酸蛋白酶。在 AsES 感知后，在多种植物物种中诱导了一系列局部和系统的防御反应，针对的是具有不同生活方式的病原体。然而，目前尚不清楚 AsES 蛋白水解活性是否是触发防御反应所必需的，或者该蛋白本身是否作为激发子发挥作用。为了研究蛋白酶活性对激活防御反应的必要性，克隆并在大肠杆菌中表达了野生型基因和活性位点（S226A）突变体的 AsES 编码序列。我们的数据表明，用失活蛋白预处理拟南芥植物，即用苯甲基磺酰氟（PMSF）抑制和突变体，导致植物对灰葡萄孢的系统抗性增强，并以类似于已报道的天然 AsES 蛋白的方式在时间上表达防御相关基因。本研究的数据表明，AsES 表现出的防御激发特性与其蛋白水解活性无关。此外，在 AsES 处理的植物中观察到一些免疫标记基因的增强表达、幼苗生长抑制和共受体 BAK1 的参与，表明 AsES 被富含亮氨酸重复受体识别为一种病原体相关分子模式。对 AsES 作用机制的理解将有助于开发新的育种策略，以在植物中赋予持久的抗性。
