Regulating role of neuropeptide PTTH releaved in Spodoptera frugiperda using RNAi- and CRISPR/Cas9-based functional genomic tools

Neurosecretory cells in the brain produce prothoracicotropic hormone (PTTH), which is carried to the corpora allata (CA) by axons running through the brain contralateral hemisphere before being secreted into hemolymph to trig-ger production and release of ecdysone. PTTH plays an important role in insect growth and metamorphosis, and it can be exploited as a potential target for pest control. Although the function of PTTH has been described in insects, various results have been reported. In this context, the PTTH neuropeptide gene in Spodoptera frugiperda was knocked down or knocked out using RNAi and CRISPR/Cas9, respectively. The development time of larval was significantly prolonged and even death during the larval molting and pupation by knocking out PTTH. However, after silencing 4th instar, pupae's body size increased significantly, but development time was not affected. PTTH is a key gene to regulate ecdysone synthesis and release, and is necessary to coordinate the growth and developmental timing of S. frugiperda. Our study demonstrated that RNAi and CRISPR/Cas9 of PTTH could cause different outcomes and hinted the advantages of using both RNAi and CRISPR/Cas9 to analyze gene function more comprehensively (than using single technique). The gene sequence structure of PTTH has more conservative characteristics, especially between similar species, which also provides convenience for developing RNAi-based pesticides.