Differential segregation and modification of mRNA during spermiogenesis in Marsilea vestita

AbstractWe are interested in the mechanisms that underlie cell fate determination in the endosporic male gametophytes of the fern, Marsilea vestita. Synchronous development is initiated by placing dry spores into water and involves the translation of stored mRNAs, with little transcription. Nine division cycles produce 32 spermatids surrounded by 7 sterile cells, and then each spermatid differentiates into a multiciliate gamete. Here, we focus on changes in the distribution of particular proteins, mRNAs, and patterns of polyadenylation as essential prerequisites for cell fate determination and gametogenesis. Earlier, we showed that α- and β-tubulin proteins become concentrated in spermatogenous initials, and that centrin mRNA is translated only in spermatogenous initials. In situ hybridizations reveal that centrin, cyclin B, and β-tubulin mRNAs are present in both sterile and spermatogenous cells, but that transcripts encoding RNA helicase and PRP-19 (a spliceosome component) become localized in spermatogenous cells. The targeted destruction of these two transcripts by RNAi treatments does not affect the numbers of division cycles, but the gametophytes exhibit anomalous patterns of cytokinesis, and a subsequent failure of spermatid differentiation. Thus, cell fate determination in the gametophyte involves localized translation, and the localization of mRNAs for proteins involved in transcript processing. We found differences in polyadenylation levels in sterile and spermatogenous cells that match the distribution of cytoplasmic poly(A) polymerase (PAP), which, in immunolocalizations, is abundant in spermatogenous cells, but undetectable in sterile cells. The activation of translation in spermatogenous initials, but not in sterile cells, may be under the control of mRNA processing enzymes, which become localized either as proteins or mRNAs in the spermatogenous subdomains before any divisions occur

Kinesin-2 and kinesin-9 have atypical functions during ciliogenesis in the male gametophyte of Marsilea vestita

Spermatogenesis in the semi-aquatic fern, Marsilea vestita, is a rapid, synchronous process that is initiated when dry microspores are placed in water. Development is post-transcriptionally driven and can be divided into two phases. The first phase consists of nine mitotic division cycles that produce 7 sterile cells and 32 spermatids. During the second phase, each spermatid differentiates into a corkscrew-shaped motile spermatozoid with ~140 cilia. Analysis of the transcriptome from the male gametophyte of Marsilea revealed that one kinesin-2 (MvKinesin-2) and two kinesin-9 s (MvKinesin-9A and MvKinesin-9B) are present during spermatid differentiation and ciliogenesis. RNAi knockdowns show that MvKinesin-2 is required for mitosis and cytokinesis in spermatogenous cells. Without MvKinesin-2, most spermatozoids contain two or more coiled microtubule ribbons with attached cilia and very large cell bodies. MvKinesin-9A is required for the correct placement of basal bodies along the organelle coil. Knockdowns of MvKinesin-9A have basal bodies and cilia that are irregularly positioned. Spermatozoid swimming behavior in MvKinesin-2 and -9A knockdowns is altered because of defects in axonemal placement or ciliogenesis. MvKinesin-2 knockdowns only quiver in place while MvKinesin-9A knockdowns swim erratically compared to controls. In contrast, spermatozoids produced after the silencing of MvKinesin-9B exhibit normal morphology and swimming behavior, though development is slower than normal for these gametes. Our results show that MvKinesin-2 and MvKinesin-9A are required for ciliogenesis and motility in the Marsilea male gametophyte; however, these kinesins display atypical roles during these processes. MvKinesin-2 is required for cytokinesis, a role not typically associated with this protein, as well as for ciliogenesis during rapid development and MvKinesin-9A is needed for the correct orientation of basal bodies. Our results are the first to investigate the kinesin-linked mechanisms that regulate ciliogenesis in a land plant.https://doi.org/10.1186/s12860-016-0107-

Masked mRNA is stored with aggregated nuclear speckles and its asymmetric redistribution requires a homolog of mago nashi

<p>Abstract</p> <p>Background</p> <p>Many rapidly developing systems rely on the regulated translation of stored transcripts for the formation of new proteins essential for morphogenesis. The microspores of the water fern <it>Marsilea vestita </it>dehydrate as they mature. During this process both mRNA and proteins required for subsequent development are stored within the microspores as they become fully desiccated and enter into senescence. At this point microspores become transcriptionally silent and remain so upon rehydration and for the remainder of spermatogenesis. Transcriptional silencing coupled with the translation of preformed RNA makes the microspore of <it>M. vestita </it>a useful system in which to study post-transcriptional regulation of RNA.</p> <p>Results</p> <p>We have characterized the distribution of mRNA as well as several conserved markers of subnuclear bodies within the nuclei of desiccating spores. During this period, nuclear speckles containing RNA were seen to aggregate forming a single large coalescence. We found that aggregated speckles contain several masked mRNA species known to be essential for spermatogenesis. During spermatogenesis masked mRNA and associated speckle proteins were shown to fragment and asymmetrically localize to spermatogenous but not sterile cells. This asymmetric localization was disrupted by RNAi knockdown of the <it>Marsilea </it>homolog of the Exon Junction Complex core component Mago nashi.</p> <p>Conclusions</p> <p>A subset of masked mRNA is stored in association with nuclear speckles during the dormant phase of microspore development in <it>M. vestita</it>. The asymmetric distribution of specific mRNAs to spermatogenous but not sterile cells mirrors their translational activities and appears to require the EJC or EJC components. This suggests a novel role for nuclear speckles in the post-transcriptional regulation of transcripts.</p

The worldwide trend to high participation higher education: dynamics of social stratification in inclusive systems

Worldwide participation in higher education now includes one-third of the age cohort and is growing at an unprecedented rate. The tendency to rapid growth, leading towards high participation systems (HPS), has spread to most middle-income and some low-income countries. Though expansion of higher education requires threshold development of the state and the middle class, it is primarily powered not by economic growth but by the ambitions of families to advance or maintain social position. However, expansion is mostly not accompanied by more equal social access to elite institutions. The quality of mass higher education is often problematic. Societies vary in the extent of upward social mobility from low-socio-economic-status backgrounds. The paper explores the intersection between stratified social backgrounds and the stratifying structures in HPS. These differentiating structures include public/private distinctions in schooling and higher education, different fields of study, binary systems and tiered hierarchies of institutions, the vertical ‘stretching’ of stratification in competitive HPS, and the unequalising effects of tuition. Larger social inequalities set limits on what education can achieve. Countries with high mobility sustain a consensus about social equality, and value rigorous and autonomous systems of learning, assessment and selection in education

Effect of packaging for consumer product selection based on toys

Prezentowany artykuł koncentruje się na przedstawieniu wyników badań dotyczących wpływu opakowania na wybór konsumenta. Badania przeprowadzono na rynku zabawek. W ich trakcie analizowano wpływ kształtu opakowania, elementów na nim zawartych, informacji oraz estetyki na dokonywanie wyborów przez konsumenta.The paper presented below focuses on the presentation of research results on the impact of packaging on consumer choice. The study was conducted on the toy market. In their analysis of the effect the shape of the packaging on it contained elements, information, and aesthetics to make the election by the consume

Wyznaczniki atrakcyjności artykułów sportowych

Prezentowana publikacja koncentruje się na jakości i cenie produktów na przykładzie polskiej marki artykułów sportowych - HiMountain. W pracy przedstawiono czynniki oddziałujące na satysfakcję klienta kupującego artykuły sportowe. Następnie dokonano analizy pomiędzy jakości ą i ceną produktów w celu określenia, o ile więcej klient jest skłonny zapłacić za produkt wyższej jakości. W dalszej części pracy porównano marki artykułów sportowych z punktu widzenia ich jakości postrzeganej przez klienta.The presented paper concentrates on quality and price of product analysis on example of Polish outdoor brand - HiMountain. We investigate factors affecting customer satisfaction of outdoor products. Then we analyse relations between quality and prices of outdoor products to determine how much more customer would like to pay for better quality product. Finally there is a comparison between outdoor brands from quality of product point of view