The nucleotide sugar transporters AtUTr1 and AtUTr3 are required for the incorporation of UDP‐glucose into the endoplasmic reticulum,are essential for pollen development and are needed for embryo sac progress in Arabidopsis thaliana

Uridine 5′‐diphosphate (UDP)‐glucose is transported into the lumen of the endoplasmic reticulum (ER), and the Arabidopsis nucleotide sugar transporter AtUTr1 has been proposed to play a role in this process; however, different lines of evidence suggest that another transporter(s) may also be involved. Here we show that AtUTr3 is involved in the transport of UDP‐glucose and is located at the ER but also at the Golgi. Insertional mutants in AtUTr3 showed no obvious phenotype. Biochemical analysis in both AtUTr1 and AtUTr3 mutants indicates that uptake of UDP‐glucose into the ER is mostly driven by these two transporters. Interestingly, the expression of AtUTr3 is induced by stimuli that trigger the unfolded protein response (UPR), a phenomenon also observed for AtUTr1, suggesting that both AtUTr1 and AtUTr3 are involved in supplying UDP‐glucose into the ER lumen when misfolded proteins are accumulated. Disruption of both AtUTr1 and AtUTr3 causes lethality. Genetic analysis showed that the atutr1 atutr3 combination was not transmitted by pollen and was poorly transmitted by the ovules. Cell biology analysis indicates that knocking out both genes leads to abnormalities in both male and female germ line development. These results show that the nucleotide sugar transporters AtUTr1 and AtUTr3 are required for the incorporation of UDP‐glucose into the ER, are essential for pollen development and are needed for embryo sac progress in Arabidopsis thaliana.     

Identification of a new sea urchin vitelline envelope sperm binding glycoprotein

The sea urchin egg vitelline envelope (VE) is composed of eight major glycopolypeptides that are heavily mannosylated and contain fucose and N-acetylglucosamine moieties based on lectin staining. In the present study, the macromolecular composition of the VE and the potential role of a purified VE glycoprotein in initial gamete binding was investigated. The VE components were solubilized from the surface of intact, dejellied eggs with dithiothreitol in divalent cation-free seawater, and analyzed using native, reduced electrophoresis and immunoblotting. Three major VE glycoproteins, VE-A, VE-B and VE-C, and one minor component, VE-D, were identified with antisera against whole VE preparations and against glutaraldehyde-fixed, unfertilized eggs. The electrophoretically purified glycoproteins resolved into a common subunit doublet and one unique subunit each of decreasing size on blots of sodium dodecylsulfate polyacrylamide gels. Lectin affinity chromatography was used for analysis and purification of reduced VE components; a glycoprotein eluted from Con A columns with methyl-mannoside comigrated with VE-B when analyzed by immunoblotting. Whole VE preparations and VE-B obtained from Con A columns were found to inhibit fertilization when preincubated with sperm, thus directly establishing a role for VE-B in gamete binding.     

Extreme genetic diversity in asexual grass thrips populations

The continuous generation of genetic variation has been proposed as one of the main factors explaining the maintenance of sexual reproduction in nature. However, populations of asexual individuals may attain high levels of genetic diversity through within‐lineage diversification, replicate transitions to asexuality from sexual ancestors and migration. How these mechanisms affect genetic variation in populations of closely related sexual and asexual taxa can therefore provide insights into the role of genetic diversity for the maintenance of sexual reproduction. Here, we evaluate patterns of intra‐ and interpopulation genetic diversity in sexual and asexual populations of Aptinothrips rufus grass thrips. Asexual A. rufus populations are found throughout the world, whereas sexual populations appear to be confined to few locations in the Mediterranean region. We found that asexual A. rufus populations are characterized by extremely high levels of genetic diversity, both in comparison with their sexual relatives and in comparison with other asexual species. Migration is extensive among asexual populations over large geographic distances, whereas close sexual populations are strongly isolated from each other. The combination of extensive migration with replicate evolution of asexual lineages, and a past demographic expansion in at least one of them, generated high local clone diversities in A. rufus. These high clone diversities in asexual populations may mimic certain benefits conferred by sex via genetic diversity and could help explain the extreme success of asexual A. rufus populations.     

CHANGE OF UBIQUITINATED PROTEINS DURING THE CELL CYCLE IN CHLAMYDOMONAS (CHLOROPHYTA)1

Changes in the amount of heat shock-related ubiquitinated proteins in Chlamydomonas were investigated during the cell cycle and gamete induction. In a division-synchronized culture induced by periodic illumination, the amount of the 28-kDa ubiquitinated protein increased during the dark phase. This increase correlated with the increase of total DNA. Such an increase was repressed when nuclear DNA replication was inhibited with aphidicolin. These results suggest that ubiquitination to form the 28-kDa protein is involved in nuclear DNA replication or during the cell cycle. The amount of 31-kDa ubiquitinated protein gradually increased throughout the light phase and decreased in the dark phase. The amount of 28-kDa ubiquitinated protein also increased during gamete induction caused by nitrogen starvation, while that of the 31-kDa did not. These results suggest that the change of ubiquitination of 28-kDa protein mat play a fundamental role in the cell cycle and gamete induction in Chlamydomonas.     

POSTMENOPAUSAL MOTHERHOOD: IMMORAL,ILLEGAL? A CASE STUDY

The paper explores the ethics of post-menopausal motherhood by looking at the case of Adriana Iliescu, the oldest woman ever to have given birth (so far). To this end, I will approach the three most common objections brought against the mother and/or against the team of healthcare professionals who made it happen: the age of the mother, the fact that she is single, the appropriateness of her motivation and of that of the medical team.     

Sex allocation in haplodiploids is mediated by egg size: evidence in the spider mite Tetranychus urticae Koch

Haplodiploid species display extraordinary sex ratios. However, a differential investment in male and female offspring might also be achieved by a differential provisioning of eggs, as observed in birds and lizards. We investigated this hypothesis in the haplodiploid spider mite Tetranychus urticae, which displays highly female-biased sex ratios. We show that egg size significantly determines not only larval size, juvenile survival and adult size, but also fertilization probability, as in marine invertebrates with external fertilization, so that female (fertilized) eggs are significantly larger than male (unfertilized) eggs. Moreover, females with on average larger eggs before fertilization produce a more female-biased sex ratio afterwards. Egg size thus mediates sex-specific egg provisioning, sex and offspring sex ratio. Finally, sex-specific egg provisioning has another major consequence: male eggs produced by mated mothers are smaller than male eggs produced by virgins, and this size difference persists in adults. Virgin females might thus have a (male) fitness advantage over mated females.     

SEXUAL PROCESSES IN THE LIFE CYCLE OF GYRODINIUM UNCATENUM (DINOPHYCEAE): A MORPHOGENETIC OVERVIEW1

Sexual processes in the life cycle of the dinoflagellate Gyrodinium uncatenum Hulburt were investigated in isolated field populations. Morphological and morphogenetic aspects of gamete production, planozygote formation, encystment, excystment, and planomeiocyte division are described from observations of living specimens, Protargol silver impregnated material and scanning electron microscope preparations. The sexual cycle was initiated by gamete formation which involved two asexual divisions of the vegetative organism. Gametes were fully differentiated following the second division and immediately capable of forming pairs. Either isogamous or anisogamous pairs were formed by the mid-ventral union of gametes. Gametes invariably joined with flagellar bases in close juxtaposition. Complete fusion of gametes required ca. 1 h, involved plasmogamy followed by karyogamy and resulted in a quadriflagellated planozygote. Planozygotes encysted in 24–48 h to yield a hypnozygote capable of overwintering in estuarine sediments. Hypnozygotes collected from sediment in late winter readily excysted upon exposure to temperatures above 15°C. A single quadriflagellated planomeiocyte emerged from the cyst and under culture conditions divided one to two days later. The four flagella were not evenly distributed at the first division and both bi- and tri-flagellated daughter cells were formed.     

Pollen-Ovule Ratio and Gamete Investment in Pedicularis （Orobanchaceae）

The Pedicularis species provides ideal materials to study floral evolution because of their substantial flower variation based on a narrow genetic basis, even though they are almost exclusively pollinated by bumblebee. These traits allow us to detect the evolutionary trends of floral parameters without considering genetic background and the difference of pollination vectors. The pollen-ovule ratio is widely used to estimate the pattern of resource investment in two sexual functions in flowering plants. Forty species representing all of the corolla types in Pedicularls were used to study pollen-ovule ratio, gamete investment, and their correlations. Results show that pollen-ovule ratio does not differ among both different corolla types and taxonomic groups. It is therefore suggested that pollen-ovule ratio should be a parallel evolution. The correlations between pollen-ovule ratio and pollen size （-）, and ovule size （＋） can be successfully explained in terms of sex allocation theory. The biological significance of such relationships was also discussed. Additionally, we analyzed the pattern of resource investment into female gamete, which has been somewhat neglected, and found that plants have different patterns of gamete investment between the two sexual functions.     

GROWTH AND PROBABLE GAMETE FORMATION IN THE MARINE DINOFLAGELLATE CERATIUM SCHRANKII1

Growth and formation of probable gametes in clonal cultures of Ceratium schrankii Kofoid isolated from the Gulf of Naples were monitored at 15, 20 and 25°C (12:12h LD period). Sustained division rates (k) of 0.15 div d ^?1 at 15°C and elevated ones at 20°C (0.27 div d^?1) and 25°C (0.25 div d^?1) were obtained. “Gamete” formation occurred at each temperature with few “gametes” observed at 15°C, and the greatest numbers at 20° and 25°C. This process in each parent cell involved two successive divisions with the first division forming tow “pregametes” which, within a few hours, divided again to form four motile unicells. These “gametes” remained motile for at least 24 h and normally survived for no longer tahn 48 h. Depending on the initial population at the onset of “gamete” formation, the impact on Ceratium populations was to cause either a momentary pause in log growth or a reversible decline in the populaiton.