Fig. 3

Circadian rhythm pathway involved in seasonal migration of Agrotis ipsilon. A Diagram of the proposed clock mechanism in A. ipsilon, including the core transcriptional feedback loop and the posttranscriptional regulation loop. Modified from Zhan et al. [9]. Heterodimers of clock (clk) and cycle (cyc) drive the transcription of period (per), timeless (tim), and mammalian-type cryptochrome (cry2). After 24 h, the PER, TIM, and CRY2 complexes cycle back into the nucleus, where CRY2 inhibits clk and cyc-mediated transcription. Casein kinase II (ckII), phosphatase 2A (pp2a), and doubletime (dbt) are involved in the posttranslational modifications of PER and TIM. Type-1 cryptochrome (cry1) mediates light entrainment and promotes TIM degradation. ∗ cry2 not present in all insects. B Location of Beihuang Island. Migrating moths of the black cutworm (BCW) were captured by vertical-pointing searchlight traps on the island during northward (from northern China to northeastern China; Migration_N) and southward migrations (from northeastern China to northern China; Migration_S). Red dotted line: northern boundary for overwintering of BCW. BCW cannot survive winters in northern China where temperatures fall below 0 ℃ (33 N). C Changes in expression of circadian rhythm genes in northward- and southward-migrating moths and tethered-flight moths compared with control strain. ***p < 0.001. D Diagram of A. ipsilon cry2 sgRNA-targeted site. sgRNA sequences are highlighted in red. E AiCry2 deficiency disrupts adult eclosion in constant darkness. Data for adult eclosion of wild type (Cry2+/+) and heterozygous (Cry2+/−) and homozygous (Cry2−/−) mutants were recorded every 2 h. Effect of genotype on eclosion time, one-way ANOVA: p < 0.004; Tukey’s post hoc test: Cry2+/+ vs. Cry2+/−, p > 0.05; Cry2+/+ vs. Cry2−/−, p < 0.05; Cry2+/− vs. Cry2−/−, p < 0.05. Black horizontal bars: subjective night; gray horizontal bars: subjective day