Utilizing Red Spotted Apollo Butterfly Transcriptome to Identify Antimicrobial Peptide Candidates against Porphyromonas gingivalis

SIMPLE SUMMARY: Infections caused by bacteria, fungi, or viruses possess serious threat to human health and life. This is well realized in the current COVID-19 pandemic scenario. Antimicrobial peptides (AMPs) are a natural line of defense in many organisms, especially insects which survive in extreme niches. Here we identified AMPs from red spotted apollo butterflies found at high altitudes in Russia, China, and Korea. The larval development stage occurs on the months of December to April, when there are very low temperatures. The insects natural defense mechanism might contribute to withstand this condition, which is our point of interest, and we utilized the genomic information to identify AMPs from red spotted butterflies. The obtained AMPs were tested against a list of pathogenic bacteria and fungi. Finally, we obtained one promising candidate active against Porphyromonas gingivalis, a causative organism for periodontitis. With further validations, this could be a lead antimicrobial agent in future. ABSTRACT: Classical antibiotics are the foremost treatment strategy against microbial infections. Overuse of this has led to the evolution of antimicrobial resistance. Antimicrobial peptides (AMPs) are natural defense elements present across many species including humans, insects, bacteria, and plants. Insect AMPs are our area of interest, because of their stronger abilities in host defense. We have deciphered AMPs from an endangered species Parnassius bremeri, commonly known as the red spotted apollo butterfly. It belongs to the second largest insect order Lepidoptera, comprised of butterflies and moths, and lives in the high altitudes of Russia, China, and Korea. We aimed at identifying the AMPs from the larvae stages. The rationale of choosing this stage is that the P. bremeri larvae development occurs at extremely low temperature conditions, which might serve as external stimuli for AMP production. RNA was isolated from larvae (L1 to L5) instar stages and subjected to next generation sequencing. The transcriptomes obtained were curated in in-silico pipelines. The peptides obtained were screened for requisite AMP physicochemical properties and in vitro antimicrobial activity. With the sequential screening and validation, we obtained fifteen candidate AMPs. One peptide TPS–032 showed promising antimicrobial activity against Porphyromonas gingivalis, a primary causative organism of periodontitis.