<Emphasis Type="Italic">Mutator</Emphasis>-like elements identified in melon,Arabidopsis and rice contain ULP1 protease domains

The transposon Mutator was first identified in maize, and is one of the most active mobile elements in plants. The Arabidopsis thaliana genome contains at least 200 Mutator-like elements (MULEs), which contain the Mutator-like transposase gene, and often additional genes. We have detected a novel type of MULEs in melon (CUMULE), which, besides the transposase, contains two ubiquitin-like specific protease-like sequences (ULP1). This element is not present in the observed location in some melon cultivars. Multiple copies of this element exist in the Cucumis melo genome, and it has been detected in other Cucurbitaceae species. Analysis of the A. thaliana genome revealed more than 90 CUMULE-like elements, containing one or two Ulp1-like sequences, although no evidence of mobility exists for these elements. We detected various putative transposable elements containing ULP1-like sequences in rice. The discovery of these MULEs in melon and Arabidopsis, and the existence of similar elements in rice and maize, suggest that a proteolytic function may be important for this subset of the MULE transposable elements. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. Nucleotide sequence data reported are available in the GenBank database under the accession number AY524004.     

Romina: A powerful strawberry with in vitro efficacy against uterine leiomyoma cells

Uterine leiom yomas are benign tumors highly prevalent in reproductive women. In thecurrent study, initially, we aimed to screen five different strawberry cultivars (Alba, Clery, Portola, Tecla, and Romina) to identify efficient cultivars in terms of phytochemical characterization and biological properties by measuring phenolic and anthocyanin content as well as antioxidant capacity, and by measuring apoptotic rate and reactive oxygen species (ROS) production in uterine leiomyoma cells. Next, we focused on the most efficient ones, cultivar Alba (A) and Romina (R) as well as Romina anthocyanin (RA) fraction for their ability to regulate oxidative phosphorylation (oxygen consumption rate [OCR]) glycolysis (extracellular acidification rate [ECAR]), and also fibrosis. Leiomyoma and myometrial cells were treated with a methanolic extract of A and R (250 μg/ml) or with RA (50 μg/ml) for 48 hr to measure OCR and ECAR, as well as gene expression associated with fibrosis. In the leiomyoma cells, RA was more effective in inducing apoptosis and increasing intracellular ROS levels, followed by R and A. In myometrial cells, all strawberry treatments increased the cellular viability and decreased ROS concentrations. Leiomyoma cells showed also a significant decrease in ECAR, especially after RA treatment, while OCR was slightly increased in both myometrial and leiomyoma cells. R and RA treatment significantly decreased collagen 1A1, fibronectin, versican, and activin A messenger RNA expression in leiomyoma cells. In conclusion, this study suggests that Romina, or its anthocyanin fraction, can be developed as a therapeutic and/or preventive agent for uterine leiomyomas, confirming the healthy effects exerted by these fruits and their bioactive compounds.     

The topological differences between visitation and pollen transport networks: a comparison in species rich communities of the Himalaya–Hengduan Mountains

Pollination networks are usually constructed and assessed by direct field observations which commonly assume that all flower visitors are true pollinators. However, this assumption is often invalid and the use of data based on mere visitors to flowers may lead to a misunderstanding of intrinsic pollination networks. Here, using a large dataset by both sampling floral visitors and analyzing their pollen loads, we constructed 32 networks pairs (visitation versus pollen transport) across one flowering season at four elevation sites in the Himalaya–Hengduan Mountains region. Pollen analysis was conducted to determine which flower visitors acted as potential pollinators (pollen vectors) or as cheaters (those not carrying pollen of the visited plants). We tested whether there were topological differences between visitation and pollen transport networks and whether different taxonomic groups of insect visitors differed in their ability to carry pollen of the visited plants. Our results indicated that there was a significantly higher degree of specialization at both the network and species levels in the pollen transport networks in contrast to the visitation networks. Modularity was lower but nestedness was higher in the visitation networks compared to the pollen transport networks. All the cheaters were identified as peripheral species and most of them contributed positively to the nested structure. This may explain in part the differences in modularity and nestedness between the two network types. Bees carried the highest proportion of pollen of the visited plants. This was followed by Coleoptera, other Hymenoptera and Diptera. Lepidoptera carried the lowest proportion of pollen of the visited plants. Our study shows that the construction of pollen transport networks could provide a more in‐depth understanding of plant–pollinator interactions. Moreover, it suggests that detecting and removing cheater interactions when studying the topology of other mutualistic networks might be also important.     

SIRT7 promotes chromosome synapsis during prophase I of female meiosis

Sirtuins are NAD⁺-dependent protein deacylases and ADP-ribosyltransferases that are involved in a wide range of cellular processes including genome homeostasis and metabolism. Sirtuins are expressed in human and mouse oocytes yet their role during female gamete development are not fully understood. Here, we investigated the role of a mammalian sirtuin member, SIRT7, in oocytes using a mouse knockout (KO) model. Sirt7 KO females have compromised fecundity characterized by a rapid fertility decline with age, suggesting the existence of a diminished oocyte pool. Accordingly, Sirt7 KO females produced fewer oocytes and ovulated fewer eggs. Because of the documented role of SIRT7 in DNA repair, we investigated whether SIRT7 regulates prophase I when meiotic recombination occurs. Sirt7 KO pachynema-like staged oocytes had approximately twofold increased γH2AX signals associated with regions with unsynapsed chromosomes. Consistent with the presence of asynaptic chromosome regions, Sirt7 KO oocytes had fewer MLH1 foci (~one less), a mark of crossover-mediated repair, than WT oocytes. Moreover, this reduced level of crossing over is consistent with an observed twofold increased incidence of aneuploidy in Metaphase II eggs. In addition, we found that acetylated lysine 18 of histone H3 (H3K18ac), an established SIRT7 substrate, was increased at asynaptic chromosome regions suggesting a functional relationship between this epigenetic mark and chromosome synapsis. Taken together, our findings demonstrate a pivotal role for SIRT7 in oocyte meiosis by promoting chromosome synapsis and have unveiled the importance of SIRT7 as novel regulator of the reproductive lifespan.

     

Eukaryotic initiation factor 6 regulates mechanical responses in endothelial cells

The repertoire of extratranslational functions of components of the protein synthesis apparatus is expanding to include control of key cell signaling networks. However, very little is known about noncanonical functions of members of the protein synthesis machinery in regulating cellular mechanics. We demonstrate that the eukaryotic initiation factor 6 (eIF6) modulates cellular mechanobiology. eIF6-depleted endothelial cells, under basal conditions, exhibit unchanged nascent protein synthesis, polysome profiles, and cytoskeleton protein expression, with minimal effects on ribosomal biogenesis. In contrast, using traction force and atomic force microscopy, we show that loss of eIF6 leads to reduced stiffness and force generation accompanied by cytoskeletal and focal adhesion defects. Mechanistically, we show that eIF6 is required for the correct spatial mechanoactivation of ERK1/2 via stabilization of an eIF6–RACK1–ERK1/2–FAK mechanocomplex, which is necessary for force-induced remodeling. These results reveal an extratranslational function for eIF6 and a novel paradigm for how mechanotransduction, the cellular cytoskeleton, and protein translation constituents are linked.