Drosophila melanogaster sperm turn more oxidative in the female.

Males and females of many species store sperm for extended periods. During storage, sperm are predicted to undergo cellular and functional changes, especially towards glycolytic energy metabolism because oxygen radicals derived from oxidative phosphorylation can affect sperm motility and fertilisation ability. However, not all species can use both major energy metabolism pathways. Here we examine the fruit fly Drosophila melanogaster and ask whether sperm metabolism can be fuelled by both glycolysis and oxidative phosphorylation, and to what extent metabolism changes during storage. Inhibiting glycolysis in vitro leads to a more oxidative state of sperm, inhibition of oxidative phosphorylation increased the glycolytic component assessed by multi-photon autofluorescence lifetime imaging (FLIM) of NAD(P)H. We further examined sperm in male and female sperm storage organs using FLIM of NAD(P)H and FAD. In intact storage organs, we find that, unexpectedly, i) sperm were more oxidative in females than males, and ii) oxidative phosphorylation increased with storage duration in females. Our observation that the relative contribution of both major energy metabolic pathways in Drosophila melanogaster sperm differs in males and females and over storage time has important evolutionary implications.

Recruiting Unicellular Algae for the Mass Production of Nanostructured Perovskites.

Functional capacities of lead halide perovskites are strongly dependent on their morphology, crystallographic texture, and internal ultrastructure on the nano- and the meso-scale. In the last decade, significant efforts are directed towards the development of novel synthesis routes that would overcome the morphological constraints provided by the physical and crystallographic properties of these materials. In contrast, various living organisms, such as unicellular algae, have the ability to mold biogenic crystals into a vast variety of intricate nano-architectured shapes while keeping their single crystalline nature. Here, using the cell wall of the dinoflagellate L. granifera as a model, sustainably harvested biogenic calcite is successfully transformed into nano-structured perovskites. Three variants of lead halide perovskites CH3 NH3 PbX3 are generated with X = Cl- , Br- and I- ; exhibiting emission peak-wavelength ranging from blue, to green, to near-infrared, respectively. The approach can be used for the mass production of nano-architectured perovskites with desired morphological, textural and, consequently, physical properties exploiting the numerous templates provided by calcite forming unicellular organisms.

Seminal fluid and sperm diluent affect sperm metabolism in an insect: Evidence from NAD(P)H and flavin adenine dinucleotide autofluorescence lifetime imaging.

Sperm metabolism is fundamental to sperm motility and male fertility. Its measurement is still in its infancy, and recommendations do not exist as to whether or how to standardize laboratory procedures. Here, using the sperm of an insect, the common bedbug, Cimex lectularius, we demonstrate that standardization of sperm metabolism is required with respect to the artificial sperm storage medium and a natural medium, the seminal fluid. We used fluorescence lifetime imaging microscopy (FLIM) in combination with time-correlated single-photon counting (TCSPC) to quantify sperm metabolism based on the fluorescent properties of autofluorescent coenzymes, NAD(P)H and flavin adenine dinucleotide. Autofluorescence lifetimes (decay times) differ for the free and protein-bound state of the co-enzymes, and their relative contributions to the lifetime signal serve to characterize the metabolic state of cells. We found that artificial storage medium and seminal fluid separately, and additively, affected sperm metabolism. In a medium containing sugars and amino acids (Grace's Insect medium), sperm showed increased glycolysis compared with a commonly used storage medium, phosphate-buffered saline (PBS). Adding seminal fluid to the sperm additionally increased oxidative phosphorylation, likely reflecting increased energy production of sperm during activation. Our study provides a protocol to measure sperm metabolism independently from motility, stresses that protocol standardizations for sperm measurements should be implemented and, for the first time, demonstrates that seminal fluid alters sperm metabolism. Equivalent protocol standardizations should be imposed on metabolic investigations of human sperm samples.

Distinct metabolic profiles in Drosophila sperm and somatic tissues revealed by two-photon NAD(P)H and FAD autofluorescence lifetime imaging.

Metabolic profiles vary across all levels of biological diversity, from cells to taxa. Two-photon fluorescence lifetime imaging microscopy (FLIM) facilitates metabolic characterisation of biological specimens by assaying the intrinsic autofluorescence of the ubiquitous coenzymes NAD(P)H and FAD. The potential of this method for characterising the diversity of organismal metabolism remains largely untapped. Using FLIM in Drosophila melanogaster, we show tissue-specificity in fluorescence lifetime that reflects variation in redox patterns. In particular, sperm cells exhibited elevated glycolysis relative to other tissues. We also show that sperm metabolism is phenotypically plastic: compared to male-stored sperm, sperm stored in the female's storage organ showed a substantial reduction in the protein-bound FAD lifetime fraction but no change in the NAD(P)H profile. This study represents the first ex vivo investigation of sperm metabolism using FLIM.

Meiotic cohesin SMC1ß provides prophase I centromeric cohesion and is required for multiple synapsis-associated functions.

Cohesin subunit SMC1ß is specific and essential for meiosis. Previous studies showed functions of SMC1ß in determining the axis-loop structure of synaptonemal complexes (SCs), in providing sister chromatid cohesion (SCC) in metaphase I and thereafter, in protecting telomere structure, and in synapsis. However, several central questions remained unanswered and concern roles of SMC1ß in SCC and synapsis and processes related to these two processes. Here we show that SMC1ß substantially supports prophase I SCC at centromeres but not along chromosome arms. Arm cohesion and some of centromeric cohesion in prophase I are provided by non-phosphorylated SMC1α. Besides supporting synapsis of autosomes, SMC1ß is also required for synapsis and silencing of sex chromosomes. In absence of SMC1ß, the silencing factor γH2AX remains associated with asynapsed autosomes and fails to localize to sex chromosomes. Microarray expression studies revealed up-regulated sex chromosome genes and many down-regulated autosomal genes. SMC1ß is further required for non-homologous chromosome associations observed in absence of SPO11 and thus of programmed double-strand breaks. These breaks are properly generated in Smc1ß⁻/⁻ spermatocytes, but their repair is delayed on asynapsed chromosomes. SMC1α alone cannot support non-homologous associations. Together with previous knowledge, three main functions of SMC1ß have emerged, which have multiple consequences for spermatocyte biology: generation of the loop-axis architecture of SCs, homologous and non-homologous synapsis, and SCC starting in early prophase I.