Transcriptome Analysis of the Regulatory Mechanism of FoxO on Wing Dimorphism in the Brown Planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)

Simple Summary The brown planthopper (BPH) Nilaparvata lugens can develop into either long-winged or short-winged adults depending on environmental stimuli received during larval stages. The transcription factor NlFoxO serves as a key regulator determining alternative wing morphs in BPH, but the underlying molecular mechanism is largely unknown. Here, we investigated the transcriptomic profile of forewing and hindwing buds across the 5th-instar stage, the wing-morph decision stage. Our results indicated that NlFoxO modulated the developmental plasticity of wing buds mainly by regulating the expression of cell proliferation-associated genes. The brown planthopper (BPH), Nilaparvata lugens, can develop into either short-winged (SW) or long-winged (LW) adults according to environmental conditions, and has long served as a model organism for exploring the mechanisms of wing polyphenism in insects. The transcription factor NlFoxO acts as a master regulator that directs the development of either SW or LW morphs, but the underlying molecular mechanism is largely unknown. Here, we microinjected SW-destined morphs with double stranded-RNA (dsRNA) targeting NlFoxO (dsNlFoxO) to change them into LW-winged morphs. In parallel, SW-destined morphs microinjected with dsRNA targeting the gene encoding green fluorescence protein (dsGfp) served as a negative control. The forewing and hindwing buds of 5th-instar nymphs collected at 24, 36, and 48 h after eclosion (hAE) were used for RNA sequencing. We obtained a minimum of 43.4 million clean reads from forewing and hindwing buds at a single developmental time. Differentially expressed genes (DEGs) were significantly enriched in various Gene Ontology (GO) terms, including cellular process, binding, and cell part. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis showed that up-regulated genes in dsNlFoxO-treated forewing and hindwing buds were largely associated with the cell cycle and DNA replication. Furthermore, most up-regulated genes displayed higher expression at 24-, and 36-hAE relative to 48 hAE, indicating that wing cells in LW-destined wings might actively proliferate during the first 36 h in 5th-instar nymphs. Our findings indicated that LW development in BPH was likely dependent on the duration of cell proliferation in the 5th-instar stage, which sheds light on the molecular basis of wing polymorphism in insects.