A conditional Orco requirement in the somatic cyst cells for maintaining spermatids in a tight bundle in Drosophila testis.

Odorant receptors (OR) heterodimerizes with the OR co-receptor (Orco), forming specific odorant-gated cation channels, which are key to odor reception at the olfactory sensory neurons (OSN). Mammalian ORs are expressed in many other tissues, including testis. However, their biological implications are yet to be fully ascertained. In the mosquito, Orco is localized along the sperm tail and is indicated to maintain fidelity. Here, we show that orco expresses in Drosophila testis. The levels are higher in the somatic cyst cells. The orco-null mutants are perfectly fertile at 25°C. At 28°C, the coiled spermatid bundles are severely disrupted. The loss of Orco also disrupts the actin cap, which forms inside the head cyst cell at the rostral ends of the spermatid nuclei after coiling, and plays a key role in preventing the abnormal release of spermatids from the cyst enclosure. Both the defects are rescued by the somatic cyst cell-specific expression of the UAS-orco transgene. These results highlight a novel role of Orco in the somatic tissue during sperm release.

From fission to fusion: A perspective on the research that won the Nobel Prize in Physiology or Medicine, 2013.

Secretion is widespread in all eukaryotic cells: all of us experience this in the course of daily life – saliva, mucus, sweat, tears, bile juice, adrenalin, etc. – the list is extremely long. How does a cell manage to repeatedly spit out some stuff without losing the rest? The answer is: through regulated vesicle trafficking within the cell. The Nobel Prize in Physiology or Medicine 2013 was awarded to Drs Randy Schekman, James E Rothman and Thomas C Südhof for their ‘discoveries of machinery regulating vesicle traffic, a major transport system in our cells’. Dr Randy Schekman and his colleagues discovered a number of genes required for vesicle trafficking from the endoplasmic reticulum (ER) and Golgi; the James E Rothman group unravelled the protein machinery that allows vesicles to bud off from the membrane and fuse to their targets; and Dr Thomas C Südhof along with his colleagues revealed how calcium ions could instruct vesicles to fuse and discharge their contents with precision. These enabled the biotechnology industry to produce a variety of pharmaceutical and industrial products like insulin and hepatitis B vaccines, in a cost-efficient manner, using yeast and tissue cultured cells.

Dynamic expression pattern of kinesin accessory protein in Drosophila.

We have identified the Drosophila homologue of the non-motor accessory subunit of kinesin-II motor complex. It is homologous to the SpKAP115 of the sea urchin, KAP3A and KAP3B of the mouse, and SMAP protein in humans. In situ hybridization using a DmKAP specific cRNA probe has revealed a dynamic pattern of expression in the developing nervous system. The staining first appears in a subset of cells in the embryonic central nervous system at stage 13 and continues till the first instar larva stage. At the third instar larva stage the staining gets restricted to a few cells in the optic lobe and in the ventral ganglion region. It has also stained a subset of sensory neurons from late stage 13 and till the first instar larva stage. The DmKAP expression pattern in the nervous system corresponds well with that of Klp64D and Klp68D as reported earlier. In addition, we have found that the DmKAP gene is constitutively expressed in the germline cells and in follicle cells during oogenesis. These cells are also stained using an antibody to KLP68D protein, but mRNA in situ hybridization using KLP64D specific probe has not stained these cells. Together these results proved a basis for further analysis of tissue specific function of DmKAP in future.