Sensory Cell Proliferation within the Olfactory Epithelium of Developing Adult Manduca sexta (Lepidoptera)

Abstract

BackgroundInsects detect a multitude of odors using a broad array of phenotypically distinct olfactory organs referred to as olfactory sensilla. Each sensillum contains one to several sensory neurons and at least three support cells; these cells arise from mitotic activities from one or a small group of defined precursor cells. Sensilla phenotypes are defined by distinct morphologies, and specificities to specific odors; these are the consequence of developmental programs expressed by associated neurons and support cells, and by selection and expression of subpopulations of olfactory genes encoding such proteins as odor receptors, odorant binding proteins, and odor degrading enzymes.Methodology/Principal FindingsWe are investigating development of the olfactory epithelium of adult M. sexta, identifying events which might establish sensilla phenotypes. In the present study, antennal tissue was examined during the first three days of an 18 day development, a period when sensory mitotic activity was previously reported to occur. Each antenna develops as a cylinder with an outward facing sensory epithelium divided into approximately 80 repeat units or annuli. Mitotic proliferation of sensory cells initiated about 20–24 hrs after pupation (a.p.), in pre-existing zones of high density cells lining the proximal and distal borders of each annulus. These high density zones were observed as early as two hr. a.p., and expanded with mitotic activity to fill the mid-annular regions by about 72 hrs a.p. Mitotic activity initiated at a low rate, increasing dramatically after 40–48 hrs a.p.; this activity was enhanced by ecdysteroids, but did not occur in animals entering pupal diapause (which is also ecdysteroid sensitive).Conclusions/SignificanceSensory proliferation initiates in narrow zones along the proximal and distal borders of each annulus; these zones rapidly expand to fill the mid-annular regions. These zones exist prior to any mitotic activity as regions of high density cells which form either at or prior to pupation. Mitotic sensitivity to ecdysteroids may be a regulatory mechanism coordinating olfactory development with the developmental choice of diapause entry.

A TRP channel is expressed in Spodoptera littoralis antennae and is potentially involved in insect olfactory transduction

“…Finally, we noticed that TRPγ was expressed in the antennae during the whole pupal and adult stages. The pupal antenna undergoes a morphological transformation to form a functional adult antennae and this morphogenesis is marked by the differentiation of olfactory sensilla with an important neuronal reorganization (Franco et al. , 2007).…”

“…Finally, we noticed that TRPγ was expressed in the antennae during the whole pupal and adult stages. The pupal antenna undergoes a morphological transformation to form a functional adult antennae and this morphogenesis is marked by the differentiation of olfactory sensilla with an important neuronal reorganization (Franco et al, 2007). In D. melanogaster, molecular and genetic experiments provide evidence for a TRP function in the developing olfactory system during the pupal period (Störtkuhl et al, 1999).…”

Positional Cloning of a Bombyx Wingless Locus flügellos (fl) Reveals a Crucial Role for fringe That Is Specific for Wing Morphogenesis

“…We are interested in understanding the difference in fng functions between Bombyx and Drosophila. It has been suggested that the developmental processes of organogenesis differ between the Lepidoptera and Drosophila (Kim 1959;Tanaka and Truman 2005;Allee et al 2006;Franco et al 2007). Drosophila imaginal organs develop from each imaginal disc in a concentric region.…”

Peripheral regulation by ecdysteroids of olfactory responsiveness in male Egyptian cotton leaf worms, Spodoptera littoralis

“…Although the roles of IP3 and DAG remain unclear, DAG/IP3 signaling may have a further role in insect olfaction (Krieger and Breer, 1999). DAG can act as an allosteric activator of protein kinase C (PKC) (Goto and Kondo, 2004; for review), which may function as the odorant co-receptor in Drosophila (Sargsyan et al, 2011). In addition, DGK may play a role in olfactory transduction (Kain et al, 2008).…”

“…However, little information is known about how these hormones affect olfactory-mediated behavior. What is known is restricted to the development (Vogt et al, 1993;Kraft et al, 1998;Schachtner et al, 2004;Franco et al, 2007) and remodeling (Lee et al, 2000;Kuo et al, 2005;Marin et al, 2005) of olfactory central neurons in larvae, pupae, and rarely adults (Cayre et al, 2000). Although some studies suggest that physiological state plays a role in peripheral modulation of olfactory-mediated behavior (Martel et al, 2009;Halem et al, 2001;Wang et al, 2003), the role of hormones on peripheral olfactory processing remains unknown.…”