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Coated vesicles provide a major mechanism for the transport of proteins through the endomembrane system of plants. Transport between the endoplasmic reticulum and the Golgi involves vesicles with COPI and COPII coats, whereas clathrin is the predominant coat in endocytosis and post-Golgi trafficking. Sorting of cargo, coat assembly, budding, and fission are all complex and tightly regulated processes that involve many proteins. The mechanisms and responsible factors are largely conserved in eukaryotes, and increasing organismal complexity tends to be associated with a greater numbers of individual family members. Among the key factors is the class of ENTH/ANTH/VHS domain-containing proteins, which link membrane subdomains, clathrin, and other adapter proteins involved in early steps of clathrin coated vesicle formation. More than 30 Arabidopsis thaliana proteins contain this domain, but their generally low sequence conservation has made functional classification difficult. Reports from the last two years have greatly expanded our knowledge of these proteins and suggest that ENTH/ANTH/VHS domain proteins are involved in various instances of clathrin-related endomembrane trafficking in plants. This review aims to summarize these new findings and discuss the broader context of clathrin-dependent plant vesicular transport.
In eukaryotes, regulated protein turnover is required during many cellular processes, including defense against pathogens. Ubiquitination and degradation of ubiquitinated proteins via the ubiquitin proteasome system (UPS) is the main pathway for the turnover of intracellular proteins in eukaryotes. The extensive utilization of the UPS in host cells makes it an ideal pivot for the manipulation of cellular processes by pathogens. Like many other Gram-negative bacteria, Xanthomonas species secrete a suite of type-III effector proteins (T3Es) into their host cells to promote virulence. Some of these T3Es exploit the plant UPS to interfere with immunity. This review summarizes T3E examples from the genus Xanthomonas with a proven or suggested interaction with the host UPS or UPS-like systems and also discusses the apparent paradox that arises from the presence of T3Es that inhibit the UPS in general while others rely on its activity for their function.
We have isolated a cDNA coding for a putative invertebrate-type dopamine receptor (Peadop2) from P. americana brain by using a PCR-based strategy. The mRNA is present in samples from brain and salivary glands. We analyzed the distribution of the PeaDOP2 receptor protein with specific affinity-purified polyclonal antibodies. On Western blots, PeaDOP2 was detected in protein samples from brain, subesophageal ganglion, thoracic ganglia, and salivary glands. In immunocytochemical experiments, we detected PeaDOP2 in neurons with their somata being located at the anterior edge of the medulla bilaterally innervating the optic lobes and projecting to the ventro-lateral protocerebrum. In order to determine the functional and pharmacological properties of the cloned receptor, we generated a cell line constitutively expressing PeaDOP2. Activation of PeaDOP2-expressing cells with dopamine induced an increase in intracellular cAMP. In contrast, a C-terminally truncated splice variant of this receptor did not exhibit any functional property by itself. The molecular and pharmacological characterization of the first dopamine receptor from P. americana provides the basis for forthcoming studies focusing on the significance of the dopaminergic system in cockroach behavior and physiology.
Zooplankton carcasses are ubiquitous in marine and freshwater systems, implicating the importance of non-predatory mortality, but both are often overlooked in ecological studies compared with predatory mortality. The development of several microscopic methods allows the distinction between live and dead zooplankton in field samples, and the reported percentages of dead zooplankton average 11.6 (minimum) to 59.8 (maximum) in marine environments, and 7.4 (minimum) to 47.6 (maximum) in fresh and inland waters. Common causes of non-predatory mortality among zooplankton include senescence, temperature change, physical and chemical stresses, parasitism and food-related factors. Carcasses resulting from non-predatory mortality may undergo decomposition leading to an increase in microbial production and a shift in microbial composition in the water column. Alternatively, sinking carcasses may contribute significantly to vertical carbon flux especially outside the phytoplankton growth seasons, and become a food source for the benthos. Global climate change is already altering freshwater ecosystems on multiple levels, and likely will have significant positive or negative effects on zooplankton non-predatory mortality. Better spatial and temporal studies of zooplankton carcasses and non-predatory mortality rates will improve our understanding of this important but under-appreciated topic.
The publication of partial and complete paleogenomes within the last few years has reinvigorated research in ancient DNA. No longer limited to short fragments of mitochondrial DNA, inference of evolutionary processes through time can now be investigated from genome-wide data sampled as far back as 700,000 years. Tremendous insights have been made, in particular regarding the hominin lineage. With rare exception, however, a paleogenomic perspective has been mired by the quality and quantity of recoverable DNA. Though conceptually simple, extracting ancient DNA remains challenging, and sequencing ancient genomes to high coverage remains prohibitively expensive for most laboratories. Still, with improvements in DNA isolation and declining sequencing costs, the taxonomic and geographic purview of paleogenomics is expanding at a rapid pace. With improved capacity to screen large numbers of samples for those with high proportions of endogenous ancient DNA, paleogenomics is poised to become a key technology to better understand recent evolutionary events.
In addition to their role as a source of reduced carbon, sugars may directly or indirectly control a wide range of activities in plant cells, through transcriptional and post-translational regulation. This control has been studied in detail using Arabidopsis thaliana, where genetic analysis offers many possibilities. Much less is known about perennial woody species. For several years, various aspects of sugar sensing and signalling have been investigated in the grape (Vitis vinifera L.) berry, an organ that accumulates high concentrations of hexoses in the vacuoles of flesh cells. Here we review various aspects of this topic: the molecular basis of sugar transport and its regulation by sugars in grapevine; the functional analysis of several sugar-induced genes; the effects of some biotic and abiotic stresses on the sugar content of the berry; and finally the effects of exogenous sugar supply on the ripening process in field conditions. A picture of complex feedback and multiprocess regulation emerges from these data.
In ecology, biodiversity-ecosystem functioning (BEE) research has seen a shift in perspective from taxonomy to function in the last two decades, with successful application of trait-based approaches. This shift offers opportunities for a deeper mechanistic understanding of the role of biodiversity in maintaining multiple ecosystem processes and services. In this paper, we highlight studies that have focused on BEE of microbial communities with an emphasis on integrating trait-based approaches to microbial ecology. In doing so, we explore some of the inherent challenges and opportunities of understanding BEE using microbial systems. For example, microbial biologists characterize communities using gene phylogenies that are often unable to resolve functional traits. Additionally, experimental designs of existing microbial BEE studies are often inadequate to unravel BEE relationships. We argue that combining eco-physiological studies with contemporary molecular tools in a trait-based framework can reinforce our ability to link microbial diversity to ecosystem processes. We conclude that such trait-based approaches are a promising framework to increase the understanding of microbial BEE relationships and thus generating systematic principles in microbial ecology and more generally ecology.
Leaves and floral organs grow to distinct, species-specific sizes and shapes. Research over the last few years has increased our understanding of how genetic pathways modulate cell proliferation and cell expansion to determine these sizes and shapes. In particular, the timing of proliferation arrest is an important point of control for organ size, and work on the regulators involved is showing how this control is achieved mechanistically and integrates environmental information. We are also beginning to understand how growth differs in different organs to produce their characteristic shapes, and how growth is integrated between different tissues that make up plant organs. Lastly, components of the general machinery in eukaryotic cells have been identified as having important roles in growth control.
Aim Patterns that relate species richness with fragment area (the species-area relationship, SAR) and with isolation (the species-isolation relationship, SIR) are well documented. However, those that relate species density - the number of species within a standardized area - with fragment area (D-SAR) or isolation (D-SIR) have not been sufficiently explored, despite the potential for such an analysis to disentangle the underlying mechanisms of SARs and SIRs. Previous spatial theory predicts that a significant D-SAR or D-SIR is unlikely to emerge in taxa with high dispersal limitation, such as plants. Furthermore, a recent model predicts that the detection and the significance of D-SARs or D-SIRs may decrease with grain size. We combined a literature review with grain size-dependent sampling in a fragmented landscape to evaluate the prevalence and grain size-dependent nature of D-SARs and D-SIRs in plants. Location Worldwide (review) and a semi-arid agro-ecosystem in Israel (case study). Methods We combined an extensive literature review of 31 D-SAR studies of plants in fragmented landscapes with an empirical study in which we analysed grain size-dependent D-SARs and D-SIRs using a grain size-dependent hierarchical sampling of species density and species richness in a fragmented, semi-arid agro-ecosystem. Results We found that significantly increasing D-SARs are rare in plant studies. Furthermore, we found that the detection of a significant D-SAR is often possible only after the data have been stratified by species, habitat or landscape characteristics. The results from our case study indicated that the significance and the slopes of both D-SARs and D-SIRs increase as grain size decreases. Main conclusions These results call for a careful consideration of scale while analysing and interpreting the responses of species richness and species density to fragmentation. Our results suggest that grain size-dependent analyses of D-SARs and D-SIRs may help to disentangle the mechanisms that generate SARs and SIRs and may enable early detection of the effects of fragmentation on plant biodiversity.
Resurrection species are a group of land plants that can tolerate extreme desiccation of their vegetative tissues during harsh drought stress, and still quickly often within hours regain normal physiological and metabolic functions following rehydration. At the molecular level, this desiccation tolerance is attributed to basal cellular mechanisms including the constitutive expression of stress-associated genes and high levels of protective metabolites present already in the absence of stress, as well as to transcriptome and metabolome reconfigurations rapidly occurring during the initial phases of drought stress. Parts of this response are conferred by unique metabolites, including a diverse array of sugars, phenolic compounds, and polyols, some of which accumulate to high concentrations within the plant cell. In addition to drought stress, these metabolites are proposed to contribute to the protection against other abiotic stresses and to an increased oxidative stress tolerance. Recently, extracts of resurrection species and particular secondary metabolites therein were reported to display biological activities of importance to medicine, with e.g. antibacterial, anticancer, antifungal, and antiviral activities, rendering them possible candidates for the development of novel drug substances as well as for cosmetics. Herein, we provide an overview of the metabolite composition of resurrection species, summarize the latest reports related to the use of natural products from resurrection plants, and outline their potential for medical applications. (C) 2014 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).