Wheat defenses display both sustained and time-of-day-specific responses to Rhopalosiphum padi (bird cherry-oat aphid) infestation over a 24-hour period

Abstract Wheat is constantly challenged by destructive pests, such as herbivores, even as it adapts to shifting environmental factors. While plant responses to herbivore infestation (hours post-infestation, hpi) are studied, how these responses are modulated by daily light-dark cycles remains poorly understood. Here, we investigate the effects of Rhopalosiphum padi aphid infestation on Svevo wheat using an RNA-seq approach, analyzing responses at multiple time points over a 24-hour infestation period. Both persistently regulated and hpi-specific plant responses were identified. Gene Ontology (GO) terms related to terpene synthesis and oxidoreductase were consistently enriched throughout the infestation period, whereas ethylene and jasmonic acid synthesis were enriched at specific hpi. Notably, daytime infestation specifically enriched GO terms for protein phosphorylation and motifs of WRKY transcription factors, indicating a crucial role for the circadian clock in shaping these defense responses. Additionally, highly correlated clustered genes revealed unique pathways, including those involved in terpene synthesis and amino acid catabolic processes. Understanding these initial single-day responses to aphid infestation may provide valuable insights into the complex plant-aphid interaction and contribute to the development of targeted defensive strategies.