Elucidating Molecular Responses to Spittlebug Attack in Paspalum regnellii

Spittlebugs cause large production losses that affect agribusiness worldwide. Understanding plant-herbivore interactions at the molecular level may be the key to developing resistant cultivars. After a nymph survival experiment, root transcriptomes were assembled from two Paspalum regnellii genotypes (BGP 248 and 344) with different first-line defense strategies, with no infestation and at two times after the initial attack of the spittlebug (Mahanarva spectabilis) nymph, thus integrating differential expression analysis and biological network modeling supplemented by root anatomical analysis. Gene Ontology terms related to different stress responses, such as salicylic acid catabolic process, were enriched in BGP 248, while some specific to spittlebugs, such as response to herbivores, were enriched in BGP 344. Enriched pathways were related to structural differences between genotypes, such as those related to cutin, suberin, and wax biosynthesis. BGP 344 also presented pathways related to induced defense, such as glutathione metabolism. Metabolic networks highlighted kinases, and coexpression networks demonstrated a complex cascade response that included lncRNAs. This study provides the first molecular insights into the defense mechanisms of P. regnellii against M. spectabilis. The genotype with the fastest response to insect attack and highest nymph mortality (BGP 344) presented kinases and an enriched glutathione pathway, in addition to constitutive barriers, such as lignin, which can make it difficult for the insect to colonize the plant.