Abstract
Spodoptera frugiperda (Lepidoptera: Noctuidae) is an insect pest native to America, which has recently spread throughout the world. Its polyphagous caterpillar attacks a wide variety of host plants, including some of great economic interest such as corn (Zea mays) and rice (Oryza sativa). These plants recognize herbivorous insects thanks to Herbivore Associated Molecular Patterns (HAMPS), such as β‐glucosidase, fatty-acid-amino acid conjugates and inceptins, present in the insect oral secretions (OS). Our objective is to study the activation of the rice defense response following herbivory and evaluate the role of the insect bacterial microbiota in this process. To this end, we used Spodoptera frugiperda larvae fed with antibiotic-treated artificial diet and showed that the treated OS (OS-) is cleared of cultivable microbiota compared to not treated larvae (OS+). The molecular characterization of the whole OS microbiota by metabarcoding is in progress. We then mimicked a caterpillar attack on rice leaves using a mechanical wounding followed by deposition of OS+ or OS- and analyzed the modulation of rice defense responses by global transcriptomic analysis (RNA-seq). We identified a set of genes involved in defense responses whose expression is specifically induced by the OS+ in comparison with the OS- treatment. These rice genes are interesting candidates for further analysis of the dialog between the OS microbiota and the plant.