Northern blot analysis of APN expression in 5th instar midguts and whole neonate larvae of Spodoptera exigua. A. Comparison of expression of APNs in midguts from control (-) and toxin-exposed larvae (1Ca). An ATP synthase transcript (ATPsyn) was used as an internal control of RNA extraction and gel loading. B. Expression of APNs in midguts from fifth instar larvae (left panel) and whole neonate larvae (right panel) of the susceptible (S) and of the Cry1Ca-resistant (R) line. Higher molecular weight bands correspond to the different APN transcripts. Lower molecular weight bands correspond to the ATPsynthase transcripts.