Novel meriolin derivatives as rapid apoptosis inducers

3-(Hetero)aryl substituted 7-azaindoles possessing multikinase inhibitor activity are readily accessed in a one-pot Masuda borylation-Suzuki coupling sequence. Several promising derivatives were identified as apoptosis inducers and, emphasizing the multikinase inhibition potential, as sphingosine kinase 2 inhibitors. Our measurements provide additional insights into the structure-activity relationship of meriolin derivatives, suggesting derivatives bearing a pyridine moiety with amino groups in 2-position as most active anticancer compounds and thus as highly promising candidates for future in vivo studies.     

Extracellular-signal-regulated kinase signalling in neurons.

Extracellular-signal-regulated kinases (ERKs) are emerging as important regulators of neuronal function. Recent advances have increased our understanding of ERK signalling at the molecular level. In particular, it has become evident that multiple second messengers, such as cyclic adenosine monophosphate, protein kinase A, calcium, and diacylglycerol, can control ERK signalling via the small G proteins Ras and Rap1. These findings may explain the role of ERKs in the regulation of activity-dependent neuronal events, such as synaptic plasticity, long-term potentiation and cell survival. Moreover, they allow us to begin to develop a model to understand both the control of ERKs at the subcellular level and the generation of ERK signal specificity.     

Acetobixan,an Inhibitor of Cellulose Synthesis Identified by Microbial Bioprospecting

In plants, cellulose biosynthesis is an essential process for anisotropic growth and therefore is an ideal target for inhibition. Based on the documented utility of small-molecule inhibitors to dissect complex cellular processes we identified a cellulose biosynthesis inhibitor (CBI), named acetobixan, by bio-prospecting among compounds secreted by endophytic microorganisms. Acetobixan was identified using a drug-gene interaction screen to sift through hundreds of endophytic microbial secretions for one that caused synergistic reduction in root expansion of the leaky AtcesA6^prc1-1 mutant. We then mined this microbial secretion for compounds that were differentially abundant compared with Bacilli that failed to mimic CBI action to isolate a lead pharmacophore. Analogs of this lead compound were screened for CBI activity, and the most potent analog was named acetobixan. In living Arabidopsis cells visualized by confocal microscopy, acetobixan treatment caused CESA particles localized at the plasma membrane (PM) to rapidly re-localize to cytoplasmic vesicles. Acetobixan inhibited ¹⁴C-Glc uptake into crystalline cellulose. Moreover, cortical microtubule dynamics were not disrupted by acetobixan, suggesting specific activity towards cellulose synthesis. Previous CBI resistant mutants such as ixr1-2, ixr2-1 or aegeus were not cross resistant to acetobixan indicating that acetobixan targets a different aspect of cellulose biosynthesis.     

Does Rap1 deserve a bad Rap?

The Ras superfamily of small G proteins is remarkable for both its diversity and physiological functions. One member, Rap1, has been implicated in a particularly wide range of biological processes, from cell proliferation and differentiation to cell adhesion. But the diversity of Rap1 has lead to contradictory reports of its effects. Originally identified as an antagonist of Ras-induced transformation, Rap1 can oppose other actions of Ras including regulation of cell growth and differentiation, integrin-dependent responses and synaptic plasticity. Furthermore, recent evidence confirms that Rap1, like Ras, can activate the MAP kinase cascade (ERK) in several cell types. These diverse functions of Rap1 underscore that the activation and action of Rap1 are regulated by complex factors that are cell-type specific.     

The Overlooked Biodiversity of Flower-Visiting Invertebrates

Estimates suggest that perhaps 40% of all invertebrate species are found in tropical rainforest canopies. Extrapolations of total diversity and food web analyses have been based almost exclusively on species inhabiting the foliage, under the assumption that foliage samples are representative of the entire canopy. We examined the validity of this assumption by comparing the density of invertebrates and the species richness of beetles across three canopy microhabitats (mature leaves, new leaves and flowers) on a one hectare plot in an Australian tropical rainforest. Specifically, we tested two hypotheses: 1) canopy invertebrate density and species richness are directly proportional to the amount of resource available; and 2) canopy microhabitats represent discrete resources that are utilised by their own specialised invertebrate communities. We show that flowers in the canopy support invertebrate densities that are ten to ten thousand times greater than on the nearby foliage when expressed on a per-unit resource biomass basis. Furthermore, species-level analyses of the beetle fauna revealed that flowers support a unique and remarkably rich fauna compared to foliage, with very little species overlap between microhabitats. We reject the hypothesis that the insect fauna on mature foliage is representative of the greater canopy community even though mature foliage comprises a very large proportion of canopy plant biomass. Although the significance of the evolutionary relationship between flowers and insects is well known with respect to plant reproduction, less is known about the importance of flowers as resources for tropical insects. Consequently, we suggest that this constitutes a more important piece of the ‘diversity jigsaw puzzle’ than has been previously recognised and could alter our understanding of the evolution of plant-herbivore interactions and food web dynamics, and provide a better foundation for accurately estimating global species richness.     

Manipulating cellulose biosynthesis by expression of mutant Arabidopsis proM24::CESA3ixr1‐2 gene in transgenic tobacco

Manipulation of the cellulose biosynthetic machinery in plants has the potential to provide insight into plant growth, morphogenesis and to create modified cellulose for anthropogenic use. Evidence exists that cellulose microfibril structure and its recalcitrance to enzymatic digestion can ameliorated via mis‐sense mutation in the primary cell wall–specific gene AtCELLULOSE SYNTHASE (CESA)3. This mis‐sense mutation has been identified based on conferring drug resistance to the cellulose inhibitory herbicide isoxaben. To examine whether it would be possible to introduce mutant CESA alleles via a transgenic approach, we overexpressed a modified version of CESA3, AtCESA3^ixr1‐2 derived from Arabidopsis thaliana L. Heynh into a different plant family, the Solanceae dicotyledon tobacco (Nicotiana tabacum L. variety Samsun NN). Specifically, a chimeric gene construct of CESA3^ixr1‐2, codon optimized for tobacco, was placed between the heterologous M24 promoter and the rbcSE9 gene terminator. The results demonstrated that the tobacco plants expressing M24‐CESA3^ixr1‐2 displayed isoxaben resistance, consistent with functionality of the mutated AtCESA3^ixr1‐2 in tobacco. Secondly, during enzymatic saccharification, transgenic leaf‐ and stem‐derived cellulose is 54%–66% and 40%–51% more efficient, respectively, compared to the wild type, illustrating translational potential of modified CESA loci. Moreover, the introduction of M24‐AtCESA3^ixr1‐2 caused aberrant spatial distribution of lignified secondary cell wall tissue and a reduction in the zone occupied by parenchyma cells.     

Glutamic acid decarboxylase 67 haplodeficiency impairs social behavior in mice

Reduced glutamic acid decarboxylase (GAD)67 expression may be causally involved in the development of social withdrawal in neuropsychiatric states such as autism, schizophrenia and bipolar disorder. In this study, we report disturbance of social behavior in male GAD67 haplodeficient mice. GAD67^+/? mice, compared to GAD67^+/+ littermates, show reduced sociability and decreased intermale aggression, but normal nest building and urine marking behavior, as well as unchanged locomotor activity and anxiety‐like behavior. Moreover, the mutants display a reduced sensitivity to both social and non‐social odors, indicating a disturbance in the detection and/or processing of socially relevant olfactory stimuli. Indeed, we observed reduced activation of the lateral septum, medial preoptic area, bed nucleus of the stria terminalis, medial and cortical amygdala upon exposure of GAD67^+/? mice to social interaction paradigm, as indicated by c‐Fos immunohistochemistry. These data suggest a disturbance of stimulus processing in the brain circuitry controlling social behavior in GAD67^+/? mice, which may provide a useful model for studying the impact of a reduced GAD67 expression on alterations of social behavior related to neuropsychiatric disorders .     

Role of the periplasmic chaperones Skp, SurA, and DegQ in outer membrane protein biogenesis in Neisseria meningitidis

The periplasmic chaperones Skp, SurA, and DegP are implicated in the biogenesis of outer membrane proteins (OMPs) in Escherichia coli. Here, we investigated whether these chaperones exert similar functions in Neisseria meningitidis. Although N. meningitidis does not contain a homolog of the protease/chaperone DegP, it does possess a homolog of another E. coli protein, DegQ, which can functionally replace DegP when overproduced. Hence, we examined whether in N. meningitidis, DegQ acts as a functional homolog of DegP. Single skp, surA, and degQ mutants were easily obtained, showing that none of these chaperones is essential in N. meningitidis. Furthermore, all combinations of double mutants were generated and no synthetic lethality was observed. The absence of SurA or DegQ did not affect OMP biogenesis. In contrast, the absence of Skp resulted in severely lower levels of the porins PorA and PorB but not of other OMPs. These decreased levels were not due to proteolytic activity of DegQ, since porin levels remained low in a skp degQ double mutant, indicating that neisserial DegQ is not a functional homolog of E. coli DegP. The absence of Skp resulted in lower expression of the porB gene, as shown by using a P(porB)-lacZ fusion. We found no cross-species complementation when Skp of E. coli or N. meningitidis was heterologously expressed in skp mutants, indicating that Skp functions in a species-specific manner. Our results demonstrate an important role for Skp but not for SurA or DegQ in OMP biogenesis in N. meningitidis.     

How do herbivorous insects respond to drought stress in trees?

Increased frequency and severity of drought, as a result of climate change, is expected to drive critical changes in plant–insect interactions that may elevate rates of tree mortality. The mechanisms that link water stress in plants to insect performance are not well understood. Here, we build on previous reviews and develop a framework that incorporates the severity and longevity of drought and captures the plant physiological adjustments that follow moderate and severe drought. Using this framework, we investigate in greater depth how insect performance responds to increasing drought severity for: (i) different feeding guilds; (ii) flush feeders and senescence feeders; (iii) specialist and generalist insect herbivores; and (iv) temperate versus tropical forest communities. We outline how intermittent and moderate drought can result in increases of carbon‐based and nitrogen‐based chemical defences, whereas long and severe drought events can result in decreases in plant secondary defence compounds. We predict that different herbivore feeding guilds will show different but predictable responses to drought events, with most feeding guilds being negatively affected by water stress, with the exception of wood borers and bark beetles during severe drought and sap‐sucking insects and leaf miners during moderate and intermittent drought. Time of feeding and host specificity are important considerations. Some insects, regardless of feeding guild, prefer to feed on younger tissues from leaf flush, whereas others are adapted to feed on senescing tissues of severely stressed trees. We argue that moderate water stress could benefit specialist insect herbivores, while generalists might prefer severe drought conditions. Current evidence suggests that insect outbreaks are shorter and more spatially restricted in tropical than in temperate forests. We suggest that future research on the impact of drought on insect communities should include (i) assessing how drought‐induced changes in various plant traits, such as secondary compound concentrations and leaf water potential, affect herbivores; (ii) food web implications for other insects and those that feed on them; and (iii) interactions between the effects on insects of increasing drought and other forms of environmental change including rising temperatures and CO₂ levels. There is a need for larger, temperate and tropical forest‐scale drought experiments to look at herbivorous insect responses and their role in tree death.