Mating system variation in Veronica (Plantaginaceae): inferences from pollen/ovule ratios and other reproductive traits

The pollen–ovule ratio (P/O) is commonly used to estimate the mode of sexual reproduction in flowering plants. In previous studies, a clear correspondence has been detected between this character and the degree of autogamy. We here investigate variation in this character and its expected correlates in the genus Veronica (Plantaginaceae). Pollen–ovule ratios of 45 species representing eleven percent of all the species in the genus were investigated and compared with results from crossing experiments from previous studies. In addition, multiple populations of 17 of the 45 studied species were sampled and a controlled‐environment experiment was conducted to evaluate the extent of intraspecific variation. Moreover, relationships between P/O and other primary and secondary reproductive characters of the Veronica flower were investigated in relation to a phylogenetic hypothesis in order to determine the phylogenetic constraints on reproductive characters. The differences in P/O among species correspond well to the diversity of mating systems in Veronica and correlate well with other floral characters such as corolla size. These characters together seem to allow a powerful and fast tool to infer mating systems. However, causes for intraspecific variation of P/O, such as different cytotypes, ecotypes or different growth conditions, need to be considered.     

Does Land-Use Intensification Decrease Plant Phylogenetic Diversity in Local Grasslands?

Phylogenetic diversity (PD) has been successfully used as a complement to classical measures of biological diversity such as species richness or functional diversity. By considering the phylogenetic history of species, PD broadly summarizes the trait space within a community. This covers amongst others complex physiological or biochemical traits that are often not considered in estimates of functional diversity, but may be important for the understanding of community assembly and the relationship between diversity and ecosystem functions. In this study we analyzed the relationship between PD of plant communities and land-use intensification in 150 local grassland plots in three regions in Germany. Specifically we asked whether PD decreases with land-use intensification and if so, whether the relationship is robust across different regions. Overall, we found that species richness decreased along land-use gradients the results however differed for common and rare species assemblages. PD only weakly decreased with increasing land-use intensity. The strength of the relationship thereby varied among regions and PD metrics used. From our results we suggest that there is no general relationship between PD and land-use intensification probably due to lack of phylogenetic conservatism in land-use sensitive traits. Nevertheless, we suggest that depending on specific regional idiosyncrasies the consideration of PD as a complement to other measures of diversity can be useful.     

Harmonising the response to DSBs: a new string in the ATM bow

Ataxia telangiestasia mutated protein (ATM) is the major kinase that initiates the DNA damage signal transduction response following exposure to ionising radiation (IR) in mammalian cells. DNA non-homologous end-joining (NHEJ) is the most significant double strand break (DSB) repair pathway in mammalian cells. ATM-defective cell lines display cell cycle checkpoint defects and show pronounced radiosensitivity. ATM signalling was previously thought to be dispensable for NHEJ. This review discusses recent findings that ATM activates an end-processing mechanism dependent upon Artemis, a nuclease that also functions to cleave the hairpin intermediate generated during V(D)J recombination. ATM/Artemis-dependent end-processing is required for the repair of a sub-fraction (approximately 10%) of DSBs induced by IR and makes a significant contribution to survival following exposure to ionising radiation. This result represents a new role for ATM and demonstrates a novel cross communication between the DNA repair and signal transduction machinery.     

Chronic Kidney Disease in Non-Diabetic Older Adults: Associated Roles of the Metabolic Syndrome,Inflammation, and Insulin Resistance

Background

The aims of the study were to examine the association between CKD and the metabolic syndrome (MetS) and its components in older adults. We also explored two possible pathways linking the metabolic syndrome with CKD: inflammation as measured by high sensitivity C-Reactive Protein (hsCRP) and insulin resistance as measured by HOMA-IR.

Methods

Community-dwelling non-diabetic 70+ adults from the Einstein Aging Study participated in the study. We defined CKD as eGFR below 60mL/min/1.73m². MetS was defined according to recent guidelines from the National Cholesterol Education Program. Binary logistic regressions were used to assess the association between the metabolic syndrome, its components and CKD with adjustments for demographics, HOMA-IR and hsCRP.

Results

Of 616 participants (mean age = 79.3 years, 65.5% female), 25% had MetS and 26.5% had CKD. Participants with CKD had a significantly higher prevalence of the MetS than individuals without CKD (34.4% vs. 24.3%). Binary logistic regression models showed that CKD was associated with MetS (OR = 1.72, 95%CI = 1.13–2.61). The association was unaltered by adjustment for hsCRP but altered by adjustment for HOMA-IR. As the number of MetS components increased the relative odds of CKD also increased. None of the individual components was independently associated with CKD.

Conclusion

MetS is associated with CKD in non-diabetic older adults. Results showed that as the number of MetS components increased so did the odds for CKD. HOMA-IR seems to be in the casual pathway linking MetS to CKD.     

A complex of Pdi1p and the mannosidase Htm1p initiates clearance of unfolded glycoproteins from the endoplasmic reticulum

Endoplasmic reticulum (ER)-resident mannosidases generate asparagine-linked oligosaccharide signals that trigger ER-associated protein degradation (ERAD) of unfolded glycoproteins. In this study, we provide in vitro evidence that a complex of the yeast protein disulfide isomerase Pdi1p and the mannosidase Htm1p processes Man(8)GlcNAc(2) carbohydrates bound to unfolded proteins, yielding Man(7)GlcNAc(2). This glycan serves as a signal for HRD ligase-mediated glycoprotein disposal. We identified a point mutation in PDI1 that prevents complex formation of the oxidoreductase with Htm1p, diminishes mannosidase activity, and delays degradation of unfolded glycoproteins in vivo. Our results show that Pdi1p is engaged in both recognition and glycan signal processing of ERAD substrates and suggest that protein folding and breakdown are not separated but interconnected processes. We propose a stochastic model for how a given glycoprotein is partitioned into folding or degradation pathways and how the flux through these pathways is adjusted to stress conditions.     

Change in the bryophyte diversity and species composition of Central European temperate broad-leaved forests since the late nineteenth century

The diversity and species composition of the bryophyte flora colonizing the forest floor, live trees and deadwood in semi-natural broad-leaved forests of northern Germany was compared between a recent survey in 2013 and historical records from around 1900. The survey was based on the comparison of presence/absence data and their interpretation with help of ecological indicator values. Total species richness has declined in bryophytes growing on the forest floor but not in the other guilds, whereas a dramatic species turnover was found for all three guilds. This turnover was apparently primarily driven by the increased atmospheric load of reactive nitrogen from anthropogenic emissions. Sensitive species were replaced by more eutrophication-tolerant bryophytes; liverworts are overrepresented among the sensitive and thus declining species. Promotion of the competitive strength of vascular plants due to increased nitrogen levels is the likely cause of the reduction of bryophyte species richness on the forest floor. Former acidification by high atmospheric sulfur dioxide loads has left an imprint in the bryophyte vegetation by having favored acidophytic species and discriminating against basiphytic species. An increase in the mean indicator value for temperature suggests a beginning effect of climate warming on the bryophyte vegetation. Change in forest structure had an apparently smaller imprint on the bryophyte diversity of the studied semi-natural forests than atmospheric chemistry and climate. In this respect, bryophytes differ from the ecologically similar lichens, where published studies from the same region showed a dramatic decline of species richness and a stronger susceptibility to forest management.     

Abscisic acid and its influence on development of the embryonal root cap,storage product and secondary metabolite accumulation in hybrid larch somatic embryos

Somatic embryos of Larix × leptoeuropaea were grown on modified MSG media with 60 M abscisic acid (ABA). These were compared to control embryos raised on the same medium without ABA. Transmission electron microscopy demonstrated that zonation of polyphenol production as well as presence of extracellular mucilage was markedly different in embryos raised with and without ABA. Idioblasts were found in subepidermal and pith regions of hypocotyls and among the subepidermal cells of cotyledons in embryos matured on ABA, but not in embryos matured without ABA. The embryonal root caps of ABA-treated embryos had substantial deposition of lipids and proteins in both the column and inner pericolumn regions, but not in the outer layer of the pericolumn. Control embryos showed no accumulation of proteins or lipids, but an increase in polyphenol accumulation, which had spread to the epidermal and sub-epidermal layers of the cotyledons and hypocotyl. Starch accumulation was similar over the course of development in embryos treated with or without ABA. Using gas chromatography-selected reaction monitoring mass spectrometry, it was shown that concentrations of ABA averaged 186 ± 17 g g^–1 dry weight (DW) in embryos raised on medium supplemented with this plant growth regulator, versus an average concentration of 55 ± 19 g g^–1 DW in embryos raised in the absence of ABA. No difference in ABA concentration was found between the root cap and the rest of ABA-treated embryos.     

Gravity perception requires statoliths settled on specific plasma membrane areas in characean rhizoids and protonemata

Summary. The noninvasive infrared laser micromanipulation technique (optical tweezers, optical trapping) and centrifugation were used to study susception and perception, the early events in the gravitropic pathway of tip-growing characean rhizoids and protonemata. Reorientation of the growth direction in both cell types was only initiated when at least 2–3 statoliths settled on specific areas of the plasma membrane. This statolith-sensitive plasma membrane area is confined to the statolith region (10–35 μm behind the tip) in positively gravitropic rhizoids, whereas in negatively gravitropic protonemata, this area is limited to the apical plasma membrane (0–10 μm). Statolith sedimentation towards the sensitive plasma membrane areas is mediated by the concerted action of actin and gravity. The process of sedimentation, the pure physical movement, of statoliths is not sufficient to initiate graviresponses in both cell types. It is concluded that specific statolith-sensitive plasma membrane areas play a crucial role in the signal transduction pathway of gravitropism. These areas may represent the primary sites for gravity perception and may transform the information derived from the gravity-induced statolith sedimentation into physiological signals which trigger the molecular mechanisms of the opposite graviresponses in characean rhizoids and protonemata. Received September 10, 2001 Accepted November 16, 2001     

Pex17p of Saccharomyces cerevisiae Is a Novel Peroxin and Component of the Peroxisomal Protein Translocation Machinery

The Saccharomyces cerevisiae pex17-1 mutant was isolated from a screen to identify mutants defective in peroxisome biogenesis. pex17-1 and pex17 null mutants fail to import matrix proteins into peroxisomes via both PTS1- and PTS2-dependent pathways. The PEX17 gene (formerly PAS9; Albertini, M., P. Rehling, R. Erdmann, W. Girzalsky, J.A.K.W. Kiel, M. Veenhuis, and W.-H Kunau. 1997. Cell. 89:83–92) encodes a polypeptide of 199 amino acids with one predicted membrane spanning region and two putative coiled-coil structures. However, localization studies demonstrate that Pex17p is a peripheral membrane protein located at the surface of peroxisomes. Particulate structures containing the peroxisomal integral membrane proteins Pex3p and Pex11p are evident in pex17 mutant cells, indicating the existence of peroxisomal remnants (“ghosts”). This finding suggests that pex17 null mutant cells are not impaired in peroxisomal membrane biogenesis. Two-hybrid studies showed that Pex17p directly binds to Pex14p, the recently proposed point of convergence for the two peroxisomal targeting signal (PTS)-dependent import pathways, and indirectly to Pex5p, the PTS1 receptor. The latter interaction requires Pex14p, indicating the potential of these three peroxins to form a trimeric complex. This conclusion is supported by immunoprecipitation experiments showing that Pex14p and Pex17p coprecipitate with both PTS receptors in the absence of Pex13p. From these and other studies we conclude that Pex17p, in addition to Pex13p and Pex14p, is the third identified component of the peroxisomal translocation machinery.