Browsing by Subject "Sensory neuron membrane protein"

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Molecular elements involved in locust olfaction
gene families in the desert locust Schistocerca gregaria
(2018) Jiang, Xingcong; Breer, Heinz
Locusts are remarkable insects due to their unique and potentially devastating phenotypic plasticity based on the local population density. While “solitarious” phase locusts avoid one another, “gregarious” locusts can form dense and highly mobile swarms, which have been feared as agricultural pests since ancient history. For this reason alone, locust biology has long been the object of intense scientific studies; moreover, from a purely scientific perspective it is of great interest to unravel the mystery underlying the phenotypic plasticity. The unique phase transition including the behavioral plasticity heavily relies on chemical communication by means of critical volatiles. It is therefore important to elucidate the mechanisms underlying locust chemosensory communication, including the identification of molecular elements involved in recognizing odorous compounds. Towards this goal, the desert locust Schistocerca gregaria, as a representative locust species, was investigated in this study. One of the key elements for recognizing odorous compounds are odorant binding proteins (OBPs). To gain insight into the repertoire of locust OBPs, genomic sequences encoding candidate OBPs from Schistocerca gregaria together with those from three other locust species were subjected to thorough comparative analyses. The results indicated that locust OBPs could be classified into several categories, namely, “classic OBPs”, “plus-C OBPs”, “minus-C OBPs” and “atypical OBPs” which reside in four major phylogenetic families (I to IV). With the aim to uncover distinct features of the various OBP types, the initial studies were concentrating on the conserved subfamilies I-A and II-A which comprise “classic OBPs”. The sequence analyses provided evidence for both common and subfamily-specific motifs as well as evolutionary clues based on the calculation of coden substitution rates, which suggested the effect of purifying selection pressure. The subfamily I-A comprised a much higher number of orthologous OBPs than subfamily II-A, which resulted in a distinct re-clustering patterns for subfamily I-A and subfamily II-A. Exploring the topographic expression pattern on the antennae revealed that OBPs of subfamily I-A were selectively expressed in sensilla basiconica and sensilla trichodea, whereas OBPs of subfamily II-A were restricted to sensilla coeloconica. Furthermore, cells expressing the subtype OBP1 were present in almost all sensilla basiconica and trichodea, whereas other subtypes were only present in subpopulations. The OBPs of subfamily II-A, were expressed in distinct subpopulations of sensilla coeloconica. Analyses of representative OBPs from the remaining phylogenetic subfamilies revealed that representative subtypes from subfamily III-A and III-B were expressed in sensilla chaetica, similarly the two representatives of subfamily I-B were also expressed in this sensillum type. The selective expression of these OBPs in sensilla chaetica was substantiated by analyzing the antennal tip, which comprises numerous sensilla chaetica. The “atypical OBP” OBP12, a representative of subfamily IV-A was found to be selectively expressed in a distinct subpopulation of sensilla coeloconica, while “plus-C OBP” OBP9, from subfamily IV-B, showed a unique expression pattern and seemed to be associate with all four sensillum types. The diversity and complex sensilla- and cellular-specific distribution implies distinct functional implications of OBP subtypes in the process of chemoreception.
The sensilla-specific expression and subcellular localization of SNMP1 and SNMP2 reveal novel insights into their roles in the antenna of the desert locust Schistocerca gregaria
(2022) Cassau, Sina; Sander, Doreen; Karcher, Thomas; Laue, Michael; Hause, Gerd; Breer, Heinz; Krieger, Jürgen
Simple Summary: The desert locust, Schistocerca gregaria, can form gigantic swarms of millions of individuals that devastate the vegetation of invaded landscapes. Locust food search, reproduction, and aggregation behaviors are triggered and controlled by complex olfactory signals. Insects detect odorants through different types of olfactory sensilla on the antenna that house olfactory sensory neurons and associated support cells, both of which express the proteins required for olfactory signaling. Among these proteins, two members of the CD36 lipid transporter/receptor family, named sensory neuron membrane proteins 1 and 2 (SNMP1 and SNMP2), are indicated to be of vital importance. Towards a better understanding of the role of the two SNMPs in the olfactory system of S. gregaria, we have analysed their antennal topography and subcellular localization using specific antibodies. The results indicate sensilla type- and cell type-specific distribution patterns of the SNMP proteins. SNMP1 was located in the receptive dendrites of subpopulations of olfactory sensory neurons as well as in the microvilli of associated support cells, suggesting a dual function of this protein, both in olfactory signal detection and in sensillum lymph maintenance, respectively. In contrast, SNMP2 was found solely in support cells and their microvilli membranes, suggesting a role limited to sensillum lymph recovery processes. Abstract: Insect olfactory sensilla house olfactory sensory neurons (OSNs) and supports cells (SCs). The olfactory sensory processes require, besides the odorant receptors (ORs), insect-specific members of the CD36 family, named sensory neuron membrane proteins (SNMPs). While SNMP1 is considered to act as a coreceptor in the OR-mediated detection of pheromones, SNMP2 was found to be expressed in SCs; however, its function is unknown. For the desert locust, Schistocerca gregaria, we previously visualized mRNA for SNMP1 in OSNs and SNMP2 mRNA in cells associated with OSN clusters. Towards an understanding of their functional implication, it is imperative to explore the cellular and the subcellular localization the SNMP proteins. Therefore, we have generated polyclonal antibodies against SNMP1 and SNMP2 and used fluorescence immunohistochemistry (FIHC) to visualize the SNMP proteins. We found SNMP1 in the somata and respective dendrites of all OSNs in trichoid sensilla and in subsets of OSNs in basiconic sensilla. Notably, SNMP1 was also detected in SCs of these sensilla types. In contrast, SNMP2 protein was only visualized in SCs of basiconic and coeloconic sensilla, but not of trichoid sensilla. Exploring the subcellular localization by electron microscopy using anti-SNMP1-ab and anti-SNMP2-ab revealed an immunogold labelling of SC microvilli bordering the sensillum lymph. Together our findings suggest a dual role of SNMP1 in the antenna of S. gregaria, in some OSN subpopulations in odor detection as well as in functions of some SCs, whereas the role of SNMP2 is limited to the functions of support cells.