Identification and expression profiling of Spodoptera litura OR18, a gene with a potential role in olfactory recognition

Abstract

The full‐length cDNA of the gene SlituOR18, encoding a candidate olfactory receptor in the antennae of the tobacco cutworm, Spodoptera litura (Fabricius) (Lepidoptera Noctuidae), was identified through homology cloning strategies using RACE (rapid amplification of cDNA ends) and PCR (polymerase chain reaction). The protein of SlituOR18 shared >80% sequence identity and the same seven transmembrane domains with other olfactory receptor 18 (OR18) proteins sequenced from noctuid moths. SlituOR18 also had a similar structure to SlituORco, encoding the olfactory co‐receptor in S. litura. The sequence between transmembrane segments IV and V was longer than other sequences between transmembrane segments, and the N‐terminus was intracytoplasmic. Analysis by qRT‐PCR showed SlituOR18 was predominantly expressed in adult moths and there was higher expression in female antennae than in male antennae. Weak expression of SlituOR18 was observed in eggs and no expression was observed in the antennae of fourth instars and 5‐day‐old pupae. In situ hybridization experiments revealed that expression of these receptor types was clearly restricted to the bases of trichodea‐type olfactory sensilla (sensillum trichodeum), that are known to contain neurons sensitive to food odor or pheromones. Our data demonstrated that both SlituORco and SlituOR18 showed diurnal changes in their relative expression level. Expression of SlituOR18 varied among geographic populations of S. litura that had been trapped in the field using synthetic pheromone lures. The mRNA expression level of SlituOR18 was similar among S. litura populations from Sichuan, Guangxi, and Hunan, and higher than in populations from Shanghai and Ningbo. We suggest that OR18 could play a critical role in olfaction in noctuid moths and is a potential target for novel pest management strategies in the future.

Molecular elements of pheromone detection in the female moth, Heliothis virescens

“…The olfactory receptor type HR18 does not belong to the previously described pheromone receptor clade (Krieger et al ., ), but is highly conserved between noctuid species and it is therefore considered to be involved in pheromone sensing (Brigaud et al ., ; Zheng et al ., ). Based on this notion we have examined whether HR18 may be coexpressed with SNMP1 and have performed two‐color FISH experiments on sections of female (Fig.…”

“…In addition, H. virescens females express the receptor type HR18 (Krieger et al , ). This receptor type is not related to the pheromone receptor clade of moths, but is highly conserved across various noctuid species; moreover, it is expressed in pheromone‐sensitive sensilla trichodea and may function as pheromone receptor (Brigaud et al ., ; Zheng et al ., ).…”

“…To explore the molecular basis for the responsiveness of females to pheromone components, here we have assessed the female antenna for the cells, which express the candidate pheromone receptors HR6 or HR11, the unique receptor HR18 (Brigaud et al ., ; Zheng et al ., ) as well as the binding proteins PBP1 and PBP2. Furthermore, we have studied the expression of the “sensory neuron membrane protein” SNMP1, which is considered as an indicator for pheromone‐responsive antennal neurons.…”

A cytochrome P450 gene plays a role in the recognition of sex pheromones in the tobacco cutworm, Spodoptera litura

“…The expression level of SlituCYP4L4 in attracted males was the highest with the 10:1 ratio but lowest with the 1:1 ratio of Z9E11‐14:OAc: Z9E12‐14:OAc sex pheromone lure mix. Variability in gene expression in moths from the different geographical populations and in moths attracted with different ratios of Z9E11‐14:OAc and Z9E12‐14:OAc was also found in olfactory receptors, which could play an important role in olfaction and pheromone recognition in S. litura (Lin et al ., ; Zhang et al ., ; Zheng et al ., ). The variable expression level for sex pheromone recognition might be a result of complex transcriptional regulation in response to environmental changes, or other factors (Shum et al ., ).…”

“…The hybridization protocol was performed as described by Zheng et al . (). Slides were then treated at 4 °C with 4% paraformaldehyde in phosphate‐buffered saline (PBS; 0.85% NaCl, 1.4 mM KH 2 PO 4 , 8 mM Na 2 HPO 4 , pH 7.1) for 30 min, 1 × PBS twice for 5 min, 0.2 M HCl for 8 min, 1 × PBS twice for 5 min, 1 × PBS with 1% Triton X‐100 (Amresco, Solon, OH, USA) for 10 min followed by a 5 min wash in 1 × PBS.…”