Molecular characterization of DSC1 orthologs in invertebrate species Ying-Jun Cui a , Lin-Lin Yu a , Hai-Jun Xu a , Ke Dong b, * , Chuan-Xi Zhang a, ** a Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Science, Zhejiang University, Hangzhou, Zhejiang 310058, China b Department of Entomology and Neuroscience and Genetics Programs, Michigan State University, East Lansing, MI 48824, USA article info Article history: Received 16 September 2011 Received in revised form 20 January 2012 Accepted 22 January 2012 Keywords: Voltage-gated cation channel Sodium channel Calcium channel Nilaparvata lugens Bombyx mori BSC1 DSC1 family abstract DSC1 and BSC1 are two founding members of a novel family of invertebrate voltage-gated cation channels with close structural and evolutionary relationships to voltage-gated sodium and calcium channels. In this study, we searched the published genome sequences for DSC1 orthologs. DSC1 orthologs were found in all 48 insect species, and in other invertebrate species belonging to phyla Mollusca, Cnidaria, Hemichordata and Echinodermata. However, DSC1 orthologs were not found in four arachnid species, Ixodes scapularis, Rhipicephalus microplus, Tetranychus urticae and Varroa destructor , two species in Annelida or any vertebrate species. We then cloned and sequenced NlSC1 and BmSC1 full-length cDNAs from the brown planthopper (Nilaparvata lugens) and the silkworm (Bombyx mori), respec- tively. NlSC1 and BmSC1 share about 50% identity with DSC1, and the expression of NlSC1 and BmSC1 transcripts was most abundant in the head and antenna in adults. All DSC1 orthologs contain a unique and conserved DEEA motif, instead of the EEEE or EEDD motif in classical calcium channels or the DEKA motif in sodium channels. Phylogenetic analyses revealed that DSC1 and its orthologs form a separate group distinct from the classical voltage-gated sodium and calcium channels and constitute a unique family of cation channels. The DSC1/BSC1-family channels could be potential targets of new and safe insecticides for pest control. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Arthropod pests are responsible for about 20e50% crop losses in global crop production and transmission of many important human and plant diseases (Thacker, 2002). Because insecticides are easy to apply, fast acting and kill most target pests, they have been used extensively for pest control since the advent of DDT. Despite their many side effects on the environment, insecticides have played an important role in increasing crop production and in protecting humans and livestock from a variety of insect pests and insect-borne diseases (Cooper and Dobson, 2007). As with drug resistance in microbes, development of resistance to insecticides threatens human welfare as a result of its potential impact on crop protection and disease transmission (Denholm et al., 2002). Therefore, there is an urgent need to discover and develop alternative insecticides that have novel modes of action or affect novel targets in pests. Voltage-gated sodium channels are critical for electrical signaling in the nervous system. Due to their crucial role in neuronal excit- ability, sodium channels are targeted by a variety of toxins derived from plants and animals, and several classes of synthetic insecticides including pyrethroid insecticides (Catterall, 1980; Dong, 2007; Zlotkin, 1999). Sodium channels consist of four homologous domains (IeIV), each having six membrane spanning segments (S1eS6). There are two sodium channel-like sequences in the genome of Drosophila melanogaster (Littleton and Ganetzky, 2000). One is para which was isolated from mutants with a temperature- sensitive paralysis phenotype (Loughney et al., 1989) and encodes a functional sodium channel (Feng et al., 1995; Warmke et al., 1997). The other one is DSC1 (Drosophila sodium channel 1), which was isolated from a Drosophila genomic library using an eel sodium channel cDNA probe (Salkoff et al., 1987). The deduced amino acid sequence and the overall domain organization of the DSC1 protein were very similar to those of known voltage-gated sodium channels and, consequently, they were initially hypothesized to code for voltage-gated sodium channels (Salkoff et al., 1987). However, BSC1 , an ortholog from the German cockroach (Blattella germanica)(Liu et al., 2001) was shown to encode a voltage-gated, Ca 2þ -selective cation channel (Zhou et al., 2004). BSC1 defines a new family of invertebrate voltage-dependent cation channels with close structural and evolutionary links to classical voltage-gated sodium and calcium channels (Zhou et al., 2004). Recent functional analysis of DSC1 in Xenopus oocytes showed that it also encodes a voltage-gated cation channel similar to BSC1 (Zhang et al., 2011). * Corresponding author. Tel.: þ1 517 432 2034; fax: þ1 517 353 5598. ** Corresponding author. Tel./fax: þ86 571 88982991. E-mail addresses: dongk@msu.edu (K. Dong), chxzhang@zju.edu.cn (C.-X. Zhang). Contents lists available at SciVerse ScienceDirect Insect Biochemistry and Molecular Biology journal homepage: www.elsevier.com/locate/ibmb 0965-1748/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibmb.2012.01.005 Insect Biochemistry and Molecular Biology 42 (2012) 353e359