Odorrana margaretae (Anura: Ranidae) is widely distributed in the southern provinces of China. Previously, 72 antimicrobial peptides (AMPs) belonging to 21 families were identified from the skin of O. margaretae, which were captured in the Hunan province. In the present study, five O. margaretae frogs were captured from the Guizhou province and a total of 28 cDNAs encoding 17 host defense peptides (HDPs) belonging to 14 families were cloned from the skin cDNA library of O. margaretae.

Among the 17 HDPs, only one (brevinin-1-Omar5) had been characterized. The distinct HDP expression profiles for O. margaretae in the previous and present study may be attributed to the environmental differences between the sampling locations and the genetic divergence among O. margaretae populations. Besides, 11 of the 17 HDPs identified in the present study were novel for ranids. In order to understand their roles in host defense reactions, three HDPs (odorranain-H-OM1, odorranain-M-OM and ranatuerin-2-OM), which possess low sequence similarity with the known amphibian HDPs, were selected for further chemical synthesis and functional analysis.Odorranain-H-OM1 showed direct antimicrobial activity against bacteria and fungi.

Odorranain-M-OM exhibited concentration-dependent anti-oxidant activity. Ranatuerin-2-OM showed lectin-like activity and could strongly hemagglutinate human intact erythrocytes with or without the presence of Ca2+. The diverse activities of HDPs implied that they may play different roles in host defense reactions of O. margaretae. 

This research has been published in Asian Herpetological Research which was supported by Chengdu Institute of Biology of CAS.