A candidate olfactory receptor subtype highly conserved across different insect orders

Abstract

Candidate olfactory receptors of the moth Heliothis virescens were found to be extremely diverse from receptors of the fruitfly Drosophila melanogaster and the mosquito Anopheles gambiae, but there is one exception. The moth receptor type HR2 shares a rather high degree of sequence identity with one olfactory receptor type both from Drosophila (Dor83b) and from Anopheles (AgamGPRor7); moreover, in contrast to all other receptors, this unique receptor type is expressed in numerous antennal neurons. Here we describe the identification of HR2 homologues in two further lepidopteran species, the moths Antheraea pernyi and Bombyx mori, which share 86-88% of their amino acids. In addition, based on RT-PCR experiments HR2 homologues were discovered in antennal cDNA of the honey bee (Apis mellifera; Hymenoptera), the blowfly (Calliphora erythrocephala; Diptera) and the mealworm (Tenebrio molitor; Coleoptera). Comparison of all HR2-related receptors revealed a high degree of sequence conservation across insect orders. In situ hybridization of antennal sections from the bee and the blowfly support the notion that HR2-related receptors are generally expressed in a very large number of antennal cells. This, together with the high degree of conservation suggests that this unique receptor subtype may fulfill a special function in chemosensory neurons of insects.

Olfactory responses in a gustatory organ of the malaria vector mosquito Anopheles gambiae

“…Heliothis virescens using whole-appendage expression surveys have revealed the presence of candidate OR transcripts in the proboscis (37,38). This result is reminiscent of physiological studies in another lepidopteran, where the labial pit organ (LPO) and its projections of Manduca sexta have defined accessory olfactory pathways that are exclusively responsive to CO 2 (39), where they play a key role in finding host plants at a distance (40,41).…”

“…In A. gambiae, 79 GPCR genes hypothesized to encode odorant receptors (AgORs) have been identified (5). Genes encoding candidate odorant receptors (ORs) are diverse, with one notable exception comprising AgOR7 and other members of a highly conserved nonconventional OR subfamily that is widely expressed throughout insect olfactory organs (2,(5)(6)(7). In addition to widespread expression in olfactory organs such as the antennae and maxillary palps of A. gambiae and Dengue virus vector mosquito Aedes aegypti, Ag͞AaOR7 has recently been localized to Ϸ25 distinct type-2 (T2) sensilla on the proboscis (8,9).…”

Evolutionary dynamics of olfactory receptor genes inDrosophilaspecies

“…In particular, the Hawaiian fruit fly grimshawi, which has many pseudogenes and partial genes, may turn out to have the largest number of functional genes. In this connection, it should be mentioned that the gene OR83b (OR49 in our notation) is known to be coexpressed with another OR gene in most olfactory receptor neurons (ORNs) (10,11) and is highly conserved even among different orders of insects (12). Yet, this gene in simulans was judged as a pseudogene because it contained a stop codon.…”

Comparing the Expression of Olfaction-Related Genes in Gypsy Moth (Lymantria dispar) Adult Females and Larvae from One Flightless and Two Flight-Capable Populations

“…Antennal transcriptomes are available for insect species belonging to several orders, including Diptera, Coleoptera, and Lepidoptera (Grosse-Wilde et al, 2011;Andersson et al, 2013;Rinker et al, 2013;Leitch et al, 2015;Zhang et al, 2015). Within the Lepidoptera, the transcriptomes of model species such as B. mori, D. plexippus, H. melpomene, H. virescens, and M. sexta have been thoroughly investigated (Krieger et al, 2003(Krieger et al, , 2004Nakagawa et al, 2005;Wanner et al, 2007;Wanner and Robertson, 2008;Tanaka et al, 2009;Briscoe et al, 2013;Koenig et al, 2015;van Schooten et al, 2016). This knowledge is rapidly expanding to other economically important species like Helicoverpa armigera, Cydia pomonella, and Spodoptera littoralis, where it could greatly aid in improving already existing and developing new semiochemical-based management strategies (Bengtsson et al, 2012;Jacquin-Joly et al, 2012;Liu et al, 2012).…”

“…All analyzed Lepidoptera species possess more OR than IR types (Croset et al, 2010;Koenig et al, 2015;van Schooten et al, 2016), and these play a role in the detection of plant volatiles as well as pheromones (Nakagawa et al, 2005;Grosse-Wilde et al, 2006, 2007Tanaka et al, 2009). In insects, OSNs associated with basiconic or trichoid sensilla express one OR gene, along with the co-receptor ORCO, which is highly conserved and broadly expressed (Krieger et al, 2003;Touhara and Vosshall, 2009). …”