BACKGROUND Plant pathogens and pests often occur together, causing damage while interfering with plant growth. The effects of phytopathogenic infections on plant–herbivore–natural enemy tri‐trophic interactions (TTIs) have been extensively investigated, but little is known about how the interval of infection influences such relationships. Here, the effect of rice plants infected by the phytopathogen Rhizoctonia solani on the herbivorous rice brown planthopper (BPH) and associated egg parasitoid Anagrus nilaparvatae over a temporal scale was examined. RESULTS Our results showed that rice plants infected by R. solani showed increased volatile profiles and significantly attracted BPH and A. nilaparvatae at 5–15 days post infection (DPI) and 5–10 DPI, respectively, when compared with healthy plants. Jasmonic acid and salicylic acid content decreased significantly in BPH‐damaged plants after 15 DPI, whereas oxalic acid accumulated soon after 5 DPI when compared with healthy plants. To adapt to adverse environment, BPH laid more eggs and developed into macropterous adults. Under field conditions, R. solani infection had no substantial effect on the arthropod community when compared with healthy plants. CONCLUSION Taken together, R. solani infection altered rice–pest–parasitoid TTIs over a temporal scale. This result will shed more light on our understanding of plant pathogen–insect cross‐talk essential for developing novel pest management strategies. © 2021 Society of Chemical Industry.

The transforming growth factor-β (TGF-β) superfamily encodes a large group of proteins, including TGF-β isoforms, bone morphogenetic proteins and activins that act through conserved cell-surface receptors and signaling co-receptors. TGF-β signaling in insects controls physiological events, including growth, development, diapause, caste determination and metamorphosis. In this study, we used the red flour beetle, Tribolium castaneum, as a model species to investigate the role of the type I TGF-β receptor, saxophone (Sax), in mediating development. Developmental and tissue-specific expression profiles indicated Sax is constitutively expressed during development with lower expression in 19- and 20-day (6th instar) larvae. RNAi knockdown of Sax in 19-day larvae prolonged developmental duration from larvae to pupae and significantly decreased pupation and adult eclosion in a dose-dependent manner. At 50 ng dsSax/larva, Sax knockdown led to an 84.4% pupation rate and 46.3% adult emergence rate. At 100 ng and 200 ng dsSax/larva, pupation was down to 75.6% and 50%, respectively, with 0% adult emergence following treatments with both doses. These phenotypes were similar to those following knockdowns of 20-hydroxyecdysone (20E) receptor genes, ecdysone receptor (EcR) or ultraspiracle protein (USP). Expression of 20E biosynthesis genes disembodied and spookier, 20E receptor genes EcR and USP, and 20E downstream genes BrC and E75, were suppressed after the Sax knockdown. Topical application of 20E on larvae treated with dsSax partially rescued the dsSax-driven defects. We can infer that the TGF-β receptor gene Sax influences larval-pupal-adult development via 20E signaling in T. castaneum.

Sterol regulatory element‐binding protein‐1c (SREBP‐1c) is a basic helix‐loop‐helix type transcription factor that regulates the fatty acid and cholesterol biosynthesis. Lepidoptera sex pheromone is a product of fatty acid biosynthesis followed by carbon chain modifications. However, the role of SREBP‐1c on sex pheromone biosynthesis remains elusive. In the present study, Helicoverpa armigera was used as a model to investigate the role of SREBP‐1c on sex pheromone biosynthesis (HaSREBP‐1c). Sequence analysis demonstrated that the open reading frame of HaSREBP‐1c consists of 3201 bp nucleotides that encode 1066 amino acid residues. Blast searches based on amino acid sequences demonstrated that HaSREBP‐1c shares higher amino acid identity with lepidopteran homologues. Development expression profiles demonstrated that HaSREBP‐1c transcript could be detected at 72 hr before adult emergence, then gradually increased, and finally reached its peak at 24 hr after adult emergence. The spatial expression pattern demonstrated that HaSREBP‐1c was ubiquitously expressed in all examined tissues. The decrease of HaSREBP‐1c messenger RNA (mRNA) levels as shown by RNA interference caused significant decreases in acetyl‐coA carboxylase (ACC) mRNA levels and subsequent sex pheromone production. Behavior analysis demonstrated that the decrease of HaSREBP‐1c mRNA level caused a significant decrease in the female’s ability to attract males. Altogether our results demonstrated that HaSREBP‐1c acts as a transcription factor to regulate ACC mRNA expression and, therefore, to influence female sex pheromone biosynthesis.