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.

中文翻译：

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真菌枯草蛋白酶AsES在拟南芥植物中引发PTI样防御反应，与其酶活性无关。

顶头孢霉引发剂枯草杆菌蛋白酶（AsES）是一种由草莓真菌病原菌A.strictum分泌的34 kDa丝氨酸蛋白酶。基于AsES感知，在多种植物物种中以及针对替代生活方式的病原体的局部和系统性诱导了一系列防御反应。但是，尚不清楚是否需要AsES蛋白水解活性才能触发防御反应，或者该蛋白本身是否可作为激发子。为了研究蛋白酶活性激活防御反应的必要性，在大肠杆菌中克隆并表达了野生型基因的AsES编码序列和活性位点上的突变体（S226A）。我们的数据表明，拟南芥的预处理蛋白质失活的植物，即被苯基甲基磺酰氟（PMSF）和突变体抑制的植物，导致对灰葡萄孢的系统抗性增强与防御相关基因的表达，其时间方式类似于已经报道的天然AsES蛋白的作用。这项研究中提供的数据表明，AsES表现出的防御能力与其蛋白水解活性无关。此外，在用AsES处理的植物中观察到的一些免疫标记基因的表达增强，幼苗生长受到抑制以及辅受体BAK1的参与表明，富含亮氨酸的重复受体将AsES识别为病原体相关的分子模式。对AsES作用机理的理解将有助于开发新的育种策略，赋予植物持久的抗性。