Gustatory organs of Drosophila melanogaster : fine structure and expression of the putative odorant-binding protein PBPRP2

Abstract

In Drosophila, as in most insects, gustation is mediated by sensory hairs located on the external and internal parts of the proboscis and on the legs and wings. We describe in detail the organization and ultrastructure of the gustatory sensilla on the labellum and legs and the distribution of PBPRP2, a putative odorant-binding protein, in the gustatory organs of Drosophila. The labellum carries two kinds of sensilla: taste bristles and taste pegs. The former have the typical morphology of gustatory sensilla and can be further subdivided into three morphological subtypes, each with a stereotyped distribution and innervation. Taste pegs have a unique morphology and are innervated by two receptor cells: one mechanoreceptor and the other a putative chemoreceptor cell. PBPRP2 is abundantly expressed in all adult gustatory organs on labellum, legs, and wings and in the internal taste organs on the proboscis. In contrast to olfactory organs, where PBPRP2 is expressed in the epidermis, this protein is absent from the epidermis of labial palps and legs. In the taste bristles of the labellum and legs, PBPRP2 is localized in the crescent-shaped lumen of the sensilla, and not in the lumen where the dendrites of the gustatory neurons are found, making a function in stimulus transport unlikely in these sensilla. In contrast, PBPRP2 in peg sensilla is expressed in the inner sensillum-lymph cavity and is in contact with the dendrites. Thus, PBPRP2 could be involved as a carrier for hydrophobic ligands, e.g., bitter tastants, in these sensilla.

Identification and Expression Analysis of Candidate Odorant-Binding Protein and Chemosensory Protein Genes by Antennal Transcriptome of Sitobion avenae

“…Aphid OBPs clustered into 10 major groups, each containing several homologous OBPs from different aphid species [26]; amino acid identities for each group (OBP1–10) were 79.17%, 90.09%, 86.78%, 88.45%, 84.10%, 78.68%, 73.84%, 89.30%, 86.75% and 91.94%, respectively, indicating high conservation among the different aphid species. Most of the orthologous sequences in the S .…”

“…Based on qPCR analyses, it has become clear that many of the identified OBP genes are highly expressed in antennae [18–25]. However, OBPs are also highly expressed in other tissues, such as legs and heads, which suggests that these OBPs might be associated with taste perception or participate in other physiological functions [26, 27]. …”

The Molecular Basis for Attractive Salt-Taste Coding in Drosophila

“…1B) (4). Sensilla contain multiple GRNs, which respond to distinct stimuli, including bitter, sweet and salty tastants (4–6).…”

“…1B) (4). Sensilla contain multiple GRNs, which respond to distinct stimuli, including bitter, sweet and salty tastants (4–6). We surveyed the physiological responses of sensilla to low salt (50 mM) and high salt (500 mM) by performing tip recordings (7) (fig.…”

From the cytoplasm into the cilium: Bon voyage

“…The outer segments of vertebrate photoreceptors measure 20–25 um in rods and 10–15 um in cones of most species 200 - 202 . Outer segments of fly sensory neurons are approximately 5–50 um long 203 , 204 . Modified from Avidor-Reiss et al, 2004.…”