Caterpillar Oral Secretion Elicits Reactive Oxygen Species in Isolated Plant Protoplasts

Abstract

Over millions of years, plants have evolved and developed several defense strategies such as spines, trichomes, toxins, and plant volatiles to either directly or indirectly defend against insect herbivores. Reactive Oxygen Species (ROS) is a signaling molecule that is suspected of signaling herbivory by activating defense cascade at the cellular level, leading to local and systemic defense gene expression. In this study, we show that tobacco hornworm caterpillar (Manduca sexta) oral secretion (OS) induces ROS in tomato (Solanum lycopersicum) protoplasts. We used a dye-based ROS imaging approach to dissect the interaction between a damaging herbivore and its host plant. Our study shows that application of Plant-Fed (PF) caterpillar OS increased ROS generation while artificial Diet-Fed (DF) caterpillar OS failed to induce ROS in isolated tomato protoplasts. The elevation in ROS generation was observed after ˜100 s and was saturated after 165 s of PF-OS application. Interestingly, the PF-OS induced ROS increase was abolished in the presence of a Ca2+ chelator BAPTA-AM, suggesting possible crosstalk between Ca2+ and ROS signaling. Targeting the pathway that triggers ROS generation could be used to develop a herbivore origin potent elicitor of plant defense gene expression (ROS elicitor) pest management research.