A Flagellar Polycystin-2 Homolog Required for Male Fertility in Drosophila

AbstractA common inherited cause of renal failure, autosomal dominant polycystic kidney disease results from mutations in either of two genes, PKD1 and PKD2, which encode polycystin-1 and polycystin-2, respectively [1]. Polycystin-2 has distant homology to TRP cation channels [2] and associates directly with polycystin-1 [3, 4]. The normal functions of polycystins are poorly understood, although recent studies indicate that they are concentrated in the primary cilia of a variety of cell types [5–8]. In this report we identified a polycystin-2 homolog in Drosophila melanogaster; this homolog localized to the distal tip of the sperm flagella. A targeted mutation in this gene, almost there (amo), caused nearly complete male sterility. The amo males produced and transferred normal amounts of motile sperm to females, but mutant sperm failed to enter the female sperm storage organs, a prerequisite for fertilization. The finding that Amo functions in sperm flagella supports a common and evolutionarily conserved role for polycystin-2 proteins in both motile and nonmotile axonemal-containing structures

Distinct sensory representations of wind and near-field sound in the Drosophila brain

Behavioural responses to wind are thought to have a critical role in controlling the dispersal and population genetics of wild Drosophila species^(1, 2), as well as their navigation in flight^3, but their underlying neurobiological basis is unknown. We show that Drosophila melanogaster, like wild-caught Drosophila strains^4, exhibits robust wind-induced suppression of locomotion in response to air currents delivered at speeds normally encountered in nature^(1, 2). Here we identify wind-sensitive neurons in Johnston's organ, an antennal mechanosensory structure previously implicated in near-field sound detection (reviewed in refs 5 and 6). Using enhancer trap lines targeted to different subsets of Johnston's organ neurons^7, and a genetically encoded calcium indicator^8, we show that wind and near-field sound (courtship song) activate distinct populations of Johnston's organ neurons, which project to different regions of the antennal and mechanosensory motor centre in the central brain. Selective genetic ablation of wind-sensitive Johnston's organ neurons in the antenna abolishes wind-induced suppression of locomotion behaviour, without impairing hearing. Moreover, different neuronal subsets within the wind-sensitive population respond to different directions of arista deflection caused by air flow and project to different regions of the antennal and mechanosensory motor centre, providing a rudimentary map of wind direction in the brain. Importantly, sound- and wind-sensitive Johnston's organ neurons exhibit different intrinsic response properties: the former are phasically activated by small, bi-directional, displacements of the aristae, whereas the latter are tonically activated by unidirectional, static deflections of larger magnitude. These different intrinsic properties are well suited to the detection of oscillatory pulses of near-field sound and laminar air flow, respectively. These data identify wind-sensitive neurons in Johnston's organ, a structure that has been primarily associated with hearing, and reveal how the brain can distinguish different types of air particle movements using a common sensory organ

The retrograde IFT dynein is required for normal function of diverse mechanosensory cilia in Drosophila

IntroductionCilia biogenesis relies on intraflagellar transport (IFT), a conserved transport mechanism which functions bi-directionally to bring protein complexes to the growing ciliary tip and recycle signaling and transport proteins between the cilium and cell body. In Drosophila, anterograde IFT is critical for assembly of sensory cilia in the neurons of both chordotonal (ch) organs, which have relatively long ciliary axonemes, and external sensory (es) organs, which have short axonemal segments with microtubules in distal sensory segments forming non-axonemal bundles. We previously isolated the beethoven (btv) mutant in a mutagenesis screen for auditory mutants. Although many btv mutant flies are deaf, some retain a small residual auditory function as determined both by behavior and by auditory electrophysiology.ResultsHere we molecularly characterize the btv gene and demonstrate that it encodes the IFT-associated dynein-2 heavy chain Dync2h1. We also describe morphological changes in Johnston’s organ as flies age to 30 days, and we find that morphological and electrophysiological phenotypes in this ch organ of btv mutants become more severe with age. We show that NompB protein, encoding the conserved IFT88 protein, an IFT complex B component, fails to be cleared from chordotonal cilia in btv mutants, instead accumulating in the distorted cilia. In macrochaete bristles, a class of es organ, btv mutants show a 50% reduction in mechanoreceptor potentials.DiscussionThus, the btv-encoded Dync2h1 functions as the retrograde IFT motor in the assembly of long ciliary axonemes in ch organs and is also important for normal function of the short ciliary axonemes in es organs

The Yeast Spore Wall Enables Spores to Survive Passage through the Digestive Tract of Drosophila

In nature, yeasts are subject to predation by flies of the genus Drosophila. In response to nutritional starvation Saccharomyces cerevisiae differentiates into a dormant cell type, termed a spore, which is resistant to many types of environmental stress. The stress resistance of the spore is due primarily to a spore wall that is more elaborate than the vegetative cell wall. We report here that S. cerevisiae spores survive passage through the gut of Drosophila melanogaster. Constituents of the spore wall that distinguish it from the vegetative cell wall are necessary for this resistance. Ascospores of the distantly related yeast Schizosaccharomyces pombe also display resistance to digestion by D. melanogaster. These results suggest that the primary function of the yeast ascospore is as a cell type specialized for dispersion by insect vectors

Mechanosensory-defective, male-sterile unc

uncoordinated (unc) mutants of Drosophila, which lack transduction in ciliated mechanosensory neurons, do not produce motile sperm. Both sensory and spermatogenesis defects are associated with disrupted ciliary structures: mutant sensory neurons have truncated cilia, and sensory neurons and spermatids show defects in axoneme ultrastructure. unc encodes a novel protein with coiled-coil segments and a LisH motif, which is expressed in type I sensory neurons and in the male germline - the only ciliogenic cells in the fly. A functional UNC-GFP fusion protein specifically localizes to both basal bodies in differentiating sensory neurons. In premeiotic spermatocytes it localizes to all four centrioles in early G2, remaining associated with them through meiosis and as they become the basal bodies for the elongating spermatid flagella. UNC is thus specifically required for normal ciliogenesis. Its localization is an early marker for the centriole-basal body transition, a central but enigmatic event in eukaryotic cell differentiation

Intraflagellar Transport Is Required in Drosophila to Differentiate Sensory Cilia but Not Sperm

AbstractBackground: Intraflagellar transport (IFT) uses kinesin II to carry a multiprotein particle to the tips of eukaryotic cilia and flagella and a nonaxonemal dynein to return it to the cell body. IFT particle proteins and motors are conserved in ciliated eukaryotes, and IFT-deficient mutants in algae, nematodes, and mammals fail to extend or maintain cilia and flagella, including sensory cilia. In Drosophila, the only ciliated cells are sensory neurons and sperm. no mechanoreceptor potential (nomp) mutations have been isolated that affect the differentiation and function of ciliated sense organs. The nompB gene is here shown to encode an IFT protein. Its mutant phenotypes reveal the consequences of an IFT defect in an insect.Results: Mechanosensory and olfactory neurons in nompB mutants have missing or defective cilia. nompB encodes the Drosophila homolog of the IFT complex B protein IFT88/Polaris/OSM-5. nompB is expressed in the ciliated sensory neurons, and a functional, tagged NOMPB protein is located in sensory cilia and around basal bodies. Surprisingly, nompB mutant males produce normally elongated, motile sperm. Neuronally restricted expression and male germline mosaic experiments show that nompB-deficient sperm are fully functional in transfer, competition, and fertilization.Conclusions: NOMPB, the Drosophila homolog of IFT88, is required for the assembly of sensory cilia but not for the extension or function of the sperm flagellum. Assembly of this extremely long axoneme is therefore independent of IFT

EB1 Is Essential during Drosophila Development and Plays a Crucial Role in the Integrity of Chordotonal Mechanosensory Organs

EB1 is a conserved microtubule plus end tracking protein considered to play crucial roles in microtubule organization and the interaction of microtubules with the cell cortex. Despite intense studies carried out in yeast and cultured cells, the role of EB1 in multicellular systems remains to be elucidated. Here, we describe the first genetic study of EB1 in developing animals. We show that one of the multiple Drosophila EB1 homologues, DmEB1, is ubiquitously expressed and has essential functions during development. Hypomorphic DmEB1 mutants show neuromuscular defects, including flightlessness and uncoordinated movement, without any general cell division defects. These defects can be partly explained by the malfunction of the chordotonal mechanosensory organs. In fact, electrophysiological measurements indicated that the auditory chordotonal organs show a reduced response to sound stimuli. The internal organization of the chordotonal organs also is affected in the mutant. Consistently, DmEB1 is enriched in those regions important for the structure and function of the organs. Therefore, DmEB1 plays a crucial role in the functional and structural integrity of the chordotonal mechanosensory organs in Drosophila

Competitive survival assays¹

1<p>For each cell type tested, cultures were mixed with WT spores and the survival in the frass relative to the WT was calculated as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002873#s4" target="_blank">Methods</a>.</p>2<p>Strains used; <i>S. cerevisiae</i> WT spores, NKY895; <i>dit1</i>, AN264; WT vegetative cells, AN117-4B.</p>3<p>Ratios are the average of four experiments.</p