Analysis and validation of predicted secretory salivary proteins in Lycorma delicatula

The spotted lanternfly (Lycorma delicatula) is an invasive pest that causes substantial damage to plants and agriculture since its arrival to the United States in 2012. Feeding primarily on the tree of heaven (Ailanthus altissima) but capable of infesting over 100 plant species, including economically important crops like grapes, it poses a threat to agricultural economies. When feeding, phloem-feeding insects secrete two types of saliva. The “gelling” saliva aids the insect during feeding because it forms a sheath around the stylet protecting it against mechanical abrasion and chemical plant defenses. The “watery” saliva is secreted during probing and active feeding from the phloem. This saliva contains the insect’s effector proteins. These effector proteins are able to suppress or modify the plant’s defenses, which allows the insects to feed with minimal to no detection from the plant. This research identifies the mechanisms by which the insect disrupts plant defenses, particularly through the secretion of salivary effector proteins. First, putative salivary effectors were identified. Then, experiments assessed the ability of these proteins to interfere with plant defenses, including ROS and calcium signaling, callose deposition, and hypersensitive responses, using Nicotiana benthamiana as a model system. In this study potentially secreted effector proteins PP7 and PP17 showed the ability to suppress cell death and PP17 shows strong evidence of reducing reactive oxygen species and calcium levels in Nicotiana benthamiana. These results suggest that these two effectors of the spotted lanternfly have a significant role in modifying plant defenses allowing this pest to feed efficiently.