## 3 Discussion
### Immunity-Related Genes and Antimicrobial Peptides  
We annotated genes related to immunity in _A. domesticus_ to better understand how these crickets respond to infection, important in insects being reared in close confines for animal feed and human consumption. Insects depend almost exclusively on an innate peptide and antimicrobial secondary metabolite forms of immunity against infections/pathogens [16; 80]. The current study did not identify analogs of classical canonical small insect antimicrobial peptides (AMPs), such as ecroproins or defensins, in the _A. domesticus_ genome. AMPs are found more in holometabolous than hemimetabolous species [81], perhaps due to sampling (i.e., originally identified in insect pupae/larvae). However, this may also be due to the poor mobility and frequent terrestrial lifestyle of insect larvae vs. nymphs (e.g., grubs/caterpillars vs. cricket/grasshopper nymphs), thus exposing holometabolous insects to a wider variety of microbial pathogens for longer periods of their life [81]. Insect immune-related proteins have activity against microbes, including _Plasmodium_ sp. [82]. However, as with much of Class Insecta, insufficient research is available to identify biological activities and potential practical applications for these proteins [16]. Given their abundance in insects and the growing scale of the insect production industry, insect antibacterial, antifungal, antiparasitic, and antiviral proteins also could be a valuable and low-cost bioresource or byproduct for future biomedical applications. Many studies have identified numerous AMPs from insects with a wide variety of efficacies against various pathogens and other potentially valuable biological activities [83; 84]. Thus, these proteins represent an untapped resource for potential therapeutic applications.  
Instead of AMPs, we found other conserved genes in the _A. domesticus_ genome assembly that may protect it from pathogens, including PGRP, GNBP, lysozyme, and phenoloxidase. We reverted to our previous transcriptome data [22] to understand how these genes are expressed in different life stages or in male vs. female adults. Two PGRP genes are increasingly expressed during early nymphal development and are more highly expressed in female than male _A. domesticus_. Eleven genes were annotated as GNBP, but only one gene, ANN16377-RA, was more highly expressed in nymphs and adults. Lysozymes and PPO are important in resistance to disease in crickets [85]. Overall, lysozyme genes were expressed higher in 1- and 2-week-old nymphs, and male and female adults, and PPO genes were expressed mostly throughout life stages. However, two PPO genes, ANN15897-RA and ANN15899-RA, were more highly expressed in newly hatched larvae and thus at a time the cricket would be upregulating immune defenses. These data will be important in developing protocols for healthy farm-reared insects, both in diagnostics and prophylatics for disease control.  
Additionally, when considering the impact of insect genetic engineering, such as work derived from this publication, insects may be an ideal host for expression and mass production of exogenous antimicrobial peptides from various species (e.g.,: crickets or mealworms may be useful as bioreactors to produce a particularly active/valuable peptide compared to other insects that may be more challenging or costly to mass produce). As such, applications are identified; given large insect biological diversity, as well as an established insect mass production industry, a massive and low-cost resource is now available for production of compounds for specific applications.