Vacuolar processing enzymes (VPEs) play an important role during regular growth and development and defence responses. Despite substantial attempts to understand the molecular basis of plant–cyst nematode interaction, the mechanism of VPEs functioning during this interaction remains unknown. The second‐stage Heterodera filipjevi juvenile penetrates host roots and induces the formation of a permanent feeding site called a syncytium. To investigate whether infection with H. filipjevi alters plant host VPEs, the studies were performed in Hordeum vulgare roots and leaves on the day of inoculation and at 7, 14 and 21 days post‐inoculation (dpi). Implementing molecular, biochemical and microscopic methods we identified reasons for modulation of barley VPE activity during interaction with H. filipjevi. Heterodera filipjevi parasitism caused a general decrease of VPE activity in infected roots, but live imaging of VPEs showed that their activity is up‐regulated in syncytia at 7 and 14 dpi and down‐regulated at 21 dpi. These findings were accompanied by tissue‐specific VPE gene expression patterns. Expression of the barley cystatin HvCPI‐4 gene was stimulated in leaves but diminished in roots upon infestation. External application of cyclotides that can be produced naturally by VPEs elicits in pre‐parasitic juveniles vesiculation of their body, enhanced formation of granules, induction of exploratory behaviour (stylet thrusts and head movements), production of reactive oxygen species (ROS) and final death by methuosis. Taken together, down‐regulation of VPE activity through nematode effectors promotes the nematode invasion rates and leads to avoidance of the induction of the plant proteolytic response and death of the invading juveniles.

中文翻译：

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大麦液泡加工酶的活性谱为植物和囊肿线虫的相互作用提供了新的见识。

液泡加工酶（VPE）在正常的生长发育和防御反应中起着重要的作用。尽管人们进行了大量尝试来了解植物-线虫线虫相互作用的分子基础，但在这种相互作用过程中，VPE的功能机制仍然未知。第二阶段的杂种海藻渗透到宿主的根部，并诱导形成称为合胞体的永久性饲喂部位。为了调查H. filipjevi感染是否会改变植物宿主VPE，在大麦中进行了研究。接种当天以及接种后（dpi）第7、14和21天的根和叶。通过实施分子，生化和显微方法，我们确定了与大肠结肠菌相互作用期间调节大麦VPE活性的原因。异型杂种寄生导致了受感染根的VPE活性普遍下降，但是VPE的实时成像显示其活性在7和14 dpi合胞时上调，而在21 dpi时下调。这些发现伴随着组织特异性VPE基因表达模式。大麦半胱氨酸蛋白酶抑制剂HvCPI-4的表达该基因在叶片中受到刺激，但在侵染时在根部减少。VPEs天然产生的环氧化物的外用会引起寄生前幼虫的身体水泡，增强颗粒形成，诱导探索行为（探针的推力和头部运动），产生活性氧（ROS）并最终死亡通过变色。综上所述，通过线虫效应子对VPE活性的下调可提高线虫的入侵率，并避免诱导植物蛋白水解反应和入侵的幼虫死亡。