The Drosophila male accessory gland has functions similar to those of the mammalian prostate gland and the seminal vesicle, and secretes accessory gland proteins into the seminal fluid. Each of the two lobes of the accessory gland is composed of two types of binucleate cell: about 1,000 main cells and 40 secondary cells. A well-known accessory gland protein, sex peptide, is secreted from the main cells and induces female postmating response to increase progeny production, whereas little is known about physiological significance of the secondary cells. The homeodomain transcriptional repressor Defective proventriculus (Dve) is strongly expressed in adult secondary cells, and its mutation resulted in loss of secondary cells, mononucleation of main cells, and reduced size of the accessory gland. dve mutant males had low fecundity despite the presence of sex peptide, and failed to induce the female postmating responses of increased egg laying and reduced sexual receptivity. RNAi-mediated dve knockdown males also had low fecundity with normally binucleate main cells. We provide the first evidence that secondary cells are crucial for male fecundity, and also that Dve activity is required for survival of the secondary cells. These findings provide new insights into a mechanism of fertility/fecundity.

BackgroundIn standard cell division, the cells undergo karyokinesis and then cytokinesis. Some cells, however, such as cardiomyocytes and hepatocytes, can produce binucleate cells by going through mitosis without cytokinesis. This cytokinesis skipping is thought to be due to the inhibition of cytokinesis machinery such as the central spindle or the contractile ring, but the mechanisms regulating it are unclear. We investigated them by characterizing the binucleation event during development of the Drosophila male accessory gland, in which all cells are binucleate.ResultsThe accessory gland cells arrested the cell cycle at 50 hours after puparium formation (APF) and in the middle of the pupal stage stopped proliferating for 5 hours. They then restarted the cell cycle and at 55 hours APF entered the M-phase synchronously. At this stage, accessory gland cells binucleated by mitosis without cytokinesis. Binucleating cells displayed the standard karyokinesis progression but also showed unusual features such as a non-round shape, spindle orientation along the apico-basal axis, and poor assembly of the central spindle. Mud, a Drosophila homolog of NuMA, regulated the processes responsible for these three features, the classical isoform MudPBD and the two newly characterized isoforms MudL and MudS regulated them differently: MudL repressed cell rounding, MudPBD and MudS oriented the spindle along the apico-basal axis, and MudS and MudL repressed central spindle assembly. Importantly, overexpression of MudS induced binucleation even in standard proliferating cells such as those in imaginal discs.ConclusionsWe characterized the binucleation in the Drosophila male accessory gland and examined mechanisms that regulated unusual morphologies of binucleating cells. We demonstrated that Mud, a microtubule binding protein regulating spindle orientation, was involved in this binucleation. We suggest that atypical functions exerted by three structurally different isoforms of Mud regulate cell rounding, spindle orientation and central spindle assembly in binucleation. We also propose that MudS is a key regulator triggering cytokinesis skipping in binucleation processes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12861-014-0046-5) contains supplementary material, which is available to authorized users.

Footpads allow insects to walk on smooth surfaces. Specifically, liquid secretions on the footpad mediate adhesiveness through Van der Waals, Coulomb, and attractive capillary forces. Although the morphology and function of the footpad are well defined, the mechanism underlying their formation remains elusive. Here, we demonstrate that footpad hair in Drosophila is formed by the elongation of the hair cells and assembly of actin filaments. Knockdown of Actin5C caused a malformation of the hair structure, resulting in reduced ability to adhere to smooth substrates. We determined that functional footpads are created when hair cells form effective frameworks with actin filament bundles, thereby shaping the hair tip and facilitating cuticular deposition. We adapted this mechanism of microstructure formation to design a new artificial adhesive device-a spatula-like fiber-framed adhesive device supported by nylon fibers with a gel material at the tip. This simple self-assembly mechanism facilitates the energy-efficient production of low-cost adhesion devices.

The Drosophila middle midgut cells derived from the endoderm develop into four distinct types of cell. Of these cells, copper cells have invaginated microvillar membranes on their apical surface, and they are involved in two distinct functions, i.e., copper absorption and acid secretion. The homeobox gene defective proventriculus (dve) is expressed in the midgut, and two transcripts, type A (∼4.9kb) and type B (∼3.5kb), have been identified. We isolated the deletion allele dve(E181) that completely removes the first exon for type-A (dve-A) transcript. Dve expression pattern in dve-A mutant background indicates that isoform switching is dynamically regulated in a cell-type specific manner. Using RNAi for dve-A, we examined spatial and temporal requirement of the Dve-A activity. Early Dve-A activity is required to repress isoform switching in copper cells, and for establishment of two gut functions. Late Dve-A activity in copper cells, but not in adjacent interstitial cells, is required for acid secretion, while the activity is redundantly required in both cells for the copper absorptive function. Furthermore, ectopic type-B expression in larval copper cells specifically impaired the copper absorptive function. These results provide insight into molecular mechanisms to establish functional specificity.

Thermoelectric properties of CuMnTe, which is antiferromagnetic with a Néel temperature T = 50 K and crystallizes in a spinel-related structure, have been investigated comprehensively here. The phase transition occurring at temperatures 463 and 723 K is studied by high-temperature X-ray diffraction (XRD) and differential scanning calorimetry (DSC), and its effect on thermoelectric properties is examined. Hypothetically CuMnTe is semiconducting according to the formula (Cu)(Mn)(Te), while experimentally it shows p-type metallic conduction behavior, exhibiting electrical conductivity σ = 2500 Ω cm and Seebeck coefficient α = 20 μV K at 325 K. Herein, we show that the carrier concentration and thus the thermoelectric transport properties could be further optimized through adding electron donors such as excess Mn. Discussions are made on the physical parameters contributing to the low thermal conductivity, including Debye temperature, speed of sound, and the Grüneisen parameter. As a result of simultaneously boosted power factor and reduced thermal conductivity, a moderately high zT = 0.65 at 680 K is obtained in an excess Mn\In co-added sample, amounting to 5 times that of the pristine CuMnTe. This value ( zT = 0.65) is the best result ever reported for spinel and spinel-related chalcogenides.