Electrophysiological response patterns of 16 olfactory neurons from the trichoid sensilla to odorant from fecal volatiles in the locust, locusta migratoria manilensis

Abstract

Locusts are the most serious pests of crops in greater part of the world. They locate their host plants primarily through olfactory cues, using antennal chemosensilla, which house olfactory receptor neurons (ORNs). Despite the great economical interest of these species, their olfactory neurons have been poorly investigated at the functional level. In this study, we have used single sensillum recordings (SSRs) to obtain response patterns of ORNs from the antennal trichoid sensilla to various chemicals in the oriental locust Locusta migratoria. On the basis of their spontaneous spike amplitudes, trichoid sensilla could be distinguished into two types, housing two or three ORNs, respectively. These two structural types could be further classified into seven functional subtypes. Nine different odorants that are present in the locust feces were used as stimulants during SSRs. In particular, benzaldehyde elicited inhibitory responses in most of the ORNs tested. Moreover, in a majority of these ORNs, the excitatory responses obtained with trans-2-hexenal or 2-heptanone was inhibited when benzaldehyde was mixed with these stimulants. At least 16 response patterns of these ORNs to nine chemicals were identified by SSRs, suggesting a high complexity of the cellular mechanisms underlying chemoreception in locusts.

A broadly tuned odorant receptor in neurons of trichoid sensilla in locust, Locusta migratoria

“…Additional confirmation needs to be performed to test the activities of these same odorants that are active in LmigOR3 transgenic Drosophila aT1 system on locust antennal trichoid sensilla, because additional families of proteins, such as odorant-binding proteins (OBPs) (Pelosi et al, 2006), and sensory neuron membrane proteins (SNMPs) (Jin et al, 2008), are believed to be involved in odorant recognition. For instance, benzaldehyde elicited inhibitory responses for all trichoid sensilla in locusts (Cui et al, 2011), but we observed weak excitatory responses from LmigOR3 expressed in transgenic flies. It is possible LmigOR3 is expressed in trichoid sensilla that have escaped previous characterization, or that the response in vivo relies on additional factors, such as OBPs (Grosse-Wilde et al, 2007; Laughin et al, 2008; Leal, 2013).…”

“…2-heptanone is the component of maize leaf volatiles (Buttery and Ling, 1984) as well as that of locust body volatiles (Li and Zhang, 2011). 2, 5-dimethylpyrazine is the component of locust body volatiles (Cui et al, 2011; Yu et al, 2007). Previously, 16 types of neurons in 7 subtypes of trichoid sensilla were identified by electrophysiology (at2-1, at2-2, at2-3, at2-4, at2-5, at3-1, at3-2) in locust antennae in response to 9 odors (octanal, hexanal, 2, 5-dimethylpyrazine, 2, 6, 6-trimethyl-2-cyclohexene-1, 4-dione, trans-2-hexenal, cyclohexanol, 2-heptanone, guaiacol, benzaldehyde) present in fecal volatiles in the locust (Cui et al, 2011).…”

“…The locust trichoid sensilla house 1–3 ORNs (Ochieng et al, 1998). Some types of ORNs in locust trichoid sensilla were identified with single sensilla recording technology (Cui et al, 2011; Ochieng and Hansson, 1999). Recently, locust odorant receptors, LmigOR1 and LmigOR2 have been demonstrated to be expressed in different neurons housed in basiconic sensilla (Xu et al, 2013).…”

Differential expression of two novel odorant receptors in the locust (Locusta migratoria)

“…ORNs expressing the same ORs were housed in electrophysiologically identical sensilla subtypes and converged to the same glomerulus in the antennal lobe. Extracellular single-unit recordings from individual olfactory sensilla have revealed that different odorants elicit responses from different subsets of ORNs, and that ORNs exhibit a remarkable diversity of response properties [3,4,21]. ORNs housed in different sensilla types expressed distinct ORs, allowing the sensilla to be characterized by their molecular and cellular properties [2,4,19,21-23].…”

The Olfactory Co-receptor Orco from the Migratory Locust (Locusta migratoria) and the Desert Locust (Schistocerca gregaria): Identification and Expression pattern

“…In locust, behaviours underlying aggregation and food seeking heavily depend on volatile compounds emitted from conspecifics or plants, respectively 2. These chemical signals are mainly detected by olfactory sensory neurons (OSNs) on the antennae 3, 4, which project their chemoreceptive dendrites into morphologically different types of cuticular hair structures (olfactory sensilla). Based on their morphology and cell numbers different types of antennal olfactory sensilla are discriminated: sensilla basiconica housing 20-50 OSNs and sensilla trichodea containing 1-3 OSNs 5, 6.…”