Identification of new insect Host Defense Peptides (HDP) from Dung Beetles (Coleoptera: Scarabaeidae) transcriptomes

Introduction The Coleoptera Scarabaeidae family is one of the most diverse groups of insects on the planet, living in complex microbiological environments. Their immune systems have evolved with the generation of host defense peptides but only a small number of these peptides have been characterized. Methods In this work two sources of information were retrieved: 1) De novo transcriptomic data from two species of neotropical Scarabidae ( Dichotomius satanas and Ontophagus curvicornis ); 2) Sequence data deposited in available databases. A BLAST-based search against the transcriptomes with a subset of sequences representative of the Host Defense Peptides (HDP). The HDP were described with the cecropin, defensin, attacin, and coleoptericin families; their physical/chemical and structural properties were described. Results This work reports 155 novel sequences of HDP identified in 9 transcriptomes from seven species from the Coleoptera order: D. satanas (n= 76; 49.03%), O. curvicornis (n= 23; 14.83%), T. dichotomus (n= 18; 11.61%), O. nigriventris (n= 10; 6.45%), Heterochelus sp (n= 6; 3.87%), O. conspicillatum (n= 18; 11.61%) and P. japonica (n= 4; 2.58%). These sequences were identified based on similarity to known HDP insect families. New members of defensins (n= 58; 37.42%), cecropins (n= 18; 11.61%), attancins (n= 41; 26.45%) and coleoptericins (n= 38; 24.52%), with their physicochemical, structural characteristics, and sequence relationship to other insect HDP were analyzed. Conclusions 155 new HDP could be identified, based on similarity to known HDP insect families on nine transcriptome sequences of seven beetle species. Highlights