Fig. 5

Proposed model of the lnc19419 ~ miR-994 ~ CPCFC regulatory cascade that mediates insecticide penetration resistance in B. dorsalis. A Expression of CHS1, CPCFC, lnc19419 and miR-994 in the MS, MR and GX strains (n = 4). B The cuticular ultrastructure of the MS, MR and GX strains. C The cuticular thickness of the MS (n = 7), MR (n = 10) and GX (n = 10) strains. Each thickness value is the mean of five randomly selected cross-sectional measurements. D Malathion penetration rate in the MS, MR and GX strains. Each eluant of MR, GX and MS strains contained 30, 50 and 50 5-day-old adult flies, respectively (n = 3). E In the MR strain, abundant lnc19419 sequesters miR-994 by competitive sponging and weakens the ability of miR-994 to suppress CPCFC. The upregulation of CPCFC and CHS1 in the MR strain provides abundant chitin and cuticular proteins for cuticular thickening, resulting in insecticide penetration resistance. The overexpression of detoxification enzymes in the epidermis cells of the MR strain enhances insecticide resistance even further by metabolizing the smaller amount of insecticide that does cross the barrier