The hydrostatic gradient, not light availability, drives height-related variation in Sequoia sempervirens (Cupressaceae) leaf anatomy

? Premise of the study: Leaves at the tops of most trees are smaller, thicker, and in many other ways different from leaves on the lowermost branches. This height-related variation in leaf structure has been explained as acclimation to differing light environments and, alternatively, as a consequence of hydrostatic, gravitational constraints on turgor pressure that reduce leaf expansion. ? Methods: To separate hydrostatic effects from those of light availability, we used anatomical analysis of height-paired samples from the inner and outer tree crowns of tall redwoods (Sequoia sempervirens). ? Key results: Height above the ground correlates much more strongly with leaf anatomy than does light availability. Leaf length, width, and mesophyll porosity all decrease linearly with height and help explain increases in leaf-mass-to-area ratio and decreases in both photosynthetic capacity and internal gas-phase conductance with increasing height. Two functional traits-leaf thickness and transfusion tissue-also increase with height and may improve water-stress tolerance. Transfusion tissue area increases enough that whole-leaf vascular volume does not change significantly with height in most trees. Transfusion tracheids become deformed with height, suggesting they may collapse under water stress and act as a hydraulic buffer that improves leaf water status and reduces the likelihood of xylem dysfunction. ? Conclusions: That such variation in leaf structure may be caused more by gravity than by light calls into question use of the terms "sun" and "shade" to describe leaves at the tops and bottoms of tall tree crowns.     

High-throughput in-field bioprospecting for cyanogenic plants and hydroxynitrile lyases

Abstract

Hydroxynitrile lyases (HNLs) are sought-after, stereo-selective biocatalysts used in the agrochemical, pharmaceutical and fine chemical industries to produce cyanohydrin enantiomers. There are several approaches for the discovery of HNLs, most of which are methodologically demanding and not suitable for high-throughput. Bioprospecting studies to date have also been constrained/limited to commercialised plants or botanical gardens, leaving a vast majority of plant species untested for HNL activity or cyanogenesis. To increase the rate of discovery of HCN liberating plants, we devised a Feigl-Anger microfuge tube that is portable and capable of high throughput detection of naturally cyanogenic plants. A workflow suitable for detecting plant candidates containing extractable, novel HNLs was subsequently applied. In this study, we screened over 600 plants for cyanogenic activity as well as the ability to degrade racemic mandelonitrile. We detected 33 plants able to degrade racemic mandelonitrile, of which, 25 were identified to the species level. Six of these plants were found to be naturally cyanogenic. Protein extracts from 5 of the naturally cyanogenic plants retained the ability to degrade racemic mandelonitrile pointing to five yet undescribed enzymes in the species Achyranthes aspera, Davallia trichomonoides, Morus mesozygia, Polypodium aureum “Mandaianum”, and Thelypteris confluens. In contrast, although Acalypha glabrata was found to be naturally cyanogenic, the protein extract did not break down racemic mandelonitrile. Here, we used racemic mandelonitrile as substrate and detected enzymes with mandelonitrile lyase activity, however, any cyanohydrin could be used as part of the approach taken here to detect novel HNLs specific to the substrate utilised.     

Earliest fossil record of bacterial-cyanobacterial mat consortia: the early Silurian Passage Creek biota (440 Ma, Virginia, USA)

Cyanobacteria in terrestrial and aquatic habitats are frequently associated with heterotrophic bacteria, and such associations are most often metabolically interactive. Functionally, the members of such bacterial–cyanobacterial consortia benefit from diverse metabolic capabilities of their associates, thus exceeding the sum of their parts. Such associations may have been just as ubiquitous in the past, but the fossil record has not produced any direct evidence for such associations to date. In this paper, we document fossil bacteria associated with a macrophytic cyanobacterial mat in the early Silurian (Llandovery) Massanutten Sandstone of Virginia, USA. Both the bacterial and the cyanobacterial cells are preserved by mineral replacement (pyrite subsequently replaced by iron oxyhydroxides) within an amorphous carbonaceous matrix which represents the common exopolysaccharide investment of the cyanobacterial colony. The bacteria are rod-shaped, over 370 nm long and 100 nm in diameter, and occur both as isolated cells and as short filaments. This occurrence represents the oldest fossil evidence for bacterial–cyanobacterial associations, documenting that such consortia were present 440 Ma ago, and revealing the potential for them to be recognized deeper in the fossil record.     

Reiterative growth in the complex adaptive architecture of the Paleozoic (Pennsylvanian) filicalean fern Kaplanopteris clavata

Reiteration is a widespread component of plant growth whose evolutionary importance in ferns is not recognized widely. We introduce and discuss the growth architecture of Kaplanopteris clavata, a fossil filicalean fern from the Pennsylvanian (ca. 305 million yeas old), focusing on types of reiteration exhibited by this species and on the adaptive and phylogenetic significance of reiteration for ferns in general. Kaplanopteris clavata combines two types of reiterative growth where growth modules are borne on fronds: (1) entire fronds derived from primary pinnae, and (2) epiphyllous plantlets. This combination of reiterative pathways, unique among fossil and living ferns, allowed K. clavata to explore ecospace through an opportunistic combination of scrambling, climbing and epiphytic growth. Kaplanopteris clavata underscores the organographic importance of fronds (as opposed to stems) in the adaptive architecture of ferns, emphasizing functional convergences between the different Baupla̋ne of ferns and angiosperms. This unique combination of reiterative pathways is interpreted as a derived condition illustrating the structural and developmental complexity achieved by some filicaleans during the first major evolutionary radiation of leptosporangiate ferns.     

Surface downregulation of major histocompatibility complex class I,PE-CAM,and ICAM-1 following de novo infection of endothelial cells with Kaposi's sarcoma-associated herpesvirus

Under selective pressure from host cytotoxic T lymphocytes, many viruses have evolved to downregulate major histocompatibility complex (MHC) class I and/or T-cell costimulatory molecules from the surface of infected cells. Kaposi's sarcoma-associated herpesvirus (KSHV) encodes two proteins, MIR-1 and MIR-2, that serve this function during lytic replication. In vivo, however, KSHV exists in a predominantly latent state, with less than 5% of infected cells expressing discernible lytic gene products. Thus, mechanisms of immune evasion that depend on genes expressed only during lytic replication are unlikely to be active in most KSHV-infected cells. As a result, we searched for evidence of similar defensive strategies extant during latency, employing culture systems that strongly favor latent KSHV infection. We measured cell surface levels of immunomodulatory proteins on both primary dermal microvascular endothelial cells (pDMVEC) infected through coculture with induced primary effusion lymphoma cells and telomerase-immortalized DMVEC infected directly with cell-free virus. Employing a panel of antibodies against several endothelial cell surface proteins, we show that de novo infection with KSHV leads to the downregulation of MHC class I, CD31 (PE-CAM), and CD54 (ICAM-I) but not CD58 (LFA-3) or CD95 (Fas). Furthermore, flow cytometry with a fluorescently labeled monoclonal antibody to the latency-associated nuclear antigen (LANA) revealed that downregulation occurred predominantly on KSHV-infected (LANA-positive) cells. Although the vast majority of infected cells displayed this downregulation, less than 1% expressed either immediate-early or late lytic proteins detectable by immunofluorescence. Together, these results suggest that downregulation of immunomodulatory proteins on the surface of target cells may represent a constitutive mode of immune evasion employed by KSHV following de novo infection.     

Intracellular Kaposi's sarcoma-associated herpesvirus load determines early loss of immune synapse components

Lifelong infection is a hallmark of all herpesviruses, and their survival depends on countering host immune defenses. The human gammaherpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV) encodes an array of proteins that contribute to immune evasion, including modulator of immune recognition 2 (MIR2), an E3 ubiquitin ligase. Exogenously expressed MIR2 downregulates the surface expression of several immune synapse proteins, including major histocompatibility complex (MHC) class 1, ICAM-1 (CD54), and PECAM (CD31). Although immunofluorescence assays detect this lytic gene in only 1 to 5% of cells within infected cultures, we have found that de novo infection of naive cells leads to the downregulation of these immune synapse components in a major proportion of the population. Investigating the possibility that low levels of MIR2 are responsible for this downregulation in the context of viral infection, we found that MIR2 transduction recapitulated the patterns of surface downregulation following de novo infection and that both MIR2 promoter activation, MIR2 expression level, and immune synapse component downregulation were proportional to the concentration of KSHV added to the culture. Additionally, MIR2-specific small interfering RNA reversed the downregulation effects. Finally, using a sensitive, high-throughput assay to detect levels of the virus in individual cells, we also observed that downregulation of MHC class I and ICAM-1 correlated with intracellular viral load. Together, these results suggest that the effects of MIR2 are gene dosage dependent and that low levels of this viral protein contribute to the widespread downregulation of immune-modulating cell surface proteins during the initial stages of KSHV infection.     

Increasement of Heterologous Expression of Recombinant Vit v 1 in Pichia pastoris KM71 by Nonionic Detergents as a Cost-effective Approach

Applied Biochemistry and Microbiology - Vit v 1 as a lipid-transfer protein is a major allergen of grapes (Vitis vinifera) that elicits food allergy in many patients in Iran. Todays, recombinant...     

The cDNA cloning and molecular evolution of reptile and pigeon lactate dehydrogenase isozymes

The cDNAs encoding lactate dehydrogenase isozymes LDH-A (muscle) and LDH-B (heart) from alligator and turtle and LDH-A, LDH-B, and LDH-C (testis) from pigeon were cloned and sequenced. The evolutionary relationships among vertebrate LDH isozymes were analyzed. Contrary to the traditional belief that the turtle lineage branched off before the divergence between the lizard/alligator and bird lineages, the turtle lineage was found to be clustered with either the alligator lineage or the alligator-bird clade, while the lizard lineage was found to have branched off before the divergence between the alligator/turtle and bird lineages. The pigeon testicular LDH-C isozyme was evidently duplicated from LDH-B (heart), so it is not orthologous to the mammalian testicular LDH-C isozymes.      

Cell-to-cell and phloem-mediated transport of potato virus X. The role of virions

Movement-deficient potato virus X (PVX) mutants tagged with the green fluorescent protein were used to investigate the role of the coat protein (CP) and triple gene block (TGB) proteins in virus movement. Mutants lacking either a functional CP or TGB were restricted to single epidermal cells. Microinjection of dextran probes into cells infected with the mutants showed that an increase in the plasmodesmal size exclusion limit was dependent on one or more of the TGB proteins and was independent of CP. Fluorescently labeled CP that was injected into epidermal cells was confined to the injected cells, showing that the CP lacks an intrinsic transport function. In additional experiments, transgenic plants expressing the PVX CP were used as rootstocks and grafted with nontransformed scions. Inoculation of the PVX CP mutants to the transgenic rootstocks resulted in cell-to-cell and systemic movement within the transgenic tissue. Translocation of the CP mutants into sink leaves of the nontransgenic scions was also observed, but infection was restricted to cells close to major veins. These results indicate that the PVX CP is transported through the phloem, unloads into the vascular tissue, and subsequently is transported between cells during the course of infection. Evidence is presented that PVX uses a novel strategy for cell-to-cell movement involving the transport of filamentous virions through plasmodesmata.