Cold adaptation in the phytopathogenic fungi causing snow molds

Snow molds are psychrophilic or psychrotrophic fungal pathogens of forage crops, winter cereals, and conifer seedlings. These fungi can grow and attack dormant plants at low temperatures under snow cover. In this review, we describe the biodiversity and physiological and biochemical characteristics of snow molds that belong to various taxa. Cold tolerance is one of the important factors related to their geographic distribution, because snow molds develop mycelia under snow cover and because they should produce intra- and extracellular enzymes active at low temperatures for growth and infection. Basidiomycetous snow molds produce extracellular antifreeze proteins. Their physiological significance is to keep the extracellular environment unfrozen. The psychrophilic ascomycete Sclerotia borealis shows normal mycelial growth under frozen conditions, which is faster than that on unfrozen media at optimal growth temperature. This fungus does not produce extracellular antifreeze proteins, but osmotic stress tolerance enables the fungus to grow at subzero temperatures. In conclusion, different taxa of snow molds have different strategies to adapt under snow cover.     

Substrate color preference and feeding by juvenile Chinese sturgeon <Emphasis Type="BoldItalic">Acipenser sinensi</Emphasis>s: exploration of a behavioral adaptation

Experiments were conducted in artificial stream tanks with juvenile Chinese sturgeon, Acipenser sinensis, captured in the Yangtze Estuary to test two null hypotheses (1) juveniles have no preference for white or black substrates, and (2) white or black substrate color has no effect on juvenile feeding efficiency on the barcheek goby,Rhinogobius giurinus, a dark-colored prey of wild juveniles. Juveniles strongly preferred white substrate. However, in feeding tests, feeding efficiency by juveniles was similar on white or black substrates. Thus, substrate color had no effect on feeding efficiency. Results suggest the innate preference for white substrate is not a visual adaptation for capturing prey on a contrasting background, but is an adaptation predisposing juveniles to seek light-colored sandy substrate where forage abundance is greatest.     

A novel β-glucosidase from <Emphasis Type="Italic">Aspergillus fumigates</Emphasis> releases diosgenin from spirostanosides of <Emphasis Type="Italic">Dioscorea zingiberensis</Emphasis> C. H. Wright (DZW)

A β-glucosidase effectively releasing diosgenin from spirostanosides of Dioscorea zingiberensis C. H. Wright (DZW), named AfG, was purified from a strain of Aspergillus fumigates. The molecular weight of AfG was 113 kDa. Analysis of protein fragments by ESI-Q-TOF indicated that AfG was a β-glucosidase. The circular dichroism spectrum suggested that the main secondary structure of AfG in Milli-Q water was α-helixes. Atomic force microscopy revealed that it was a globular protein. AfG maintained high activity from pH 3.6 to 5.0 and from 50 to 90°C. With the strong heat stability, AfG retained 55% of its original activity at 65°C for 120 h. AfG utilized muti-3-O-glycosides of various steroidal saponins from DZW as substrate, such as trillin, diosgenin diglucoside, dioscin, deltonin and gracillin, to yield diosgenin, suggesting the possibility of producing diosgenin from total saponins of DZW using a single enzyme.     

Enhancement of Anaerobic Digestion Using Particulate Growth Systems

Attached media reactors are used for enhancement of wastewater treatment processes including anaerobic condition. Selection of a suitable biofilm carrier is a compelling method to improve anaerobic digestion systems. This study investigates the performance of four fibrous biofilms installed in batch biogas reactors for treatment of cow manure. BioCords HS1, HS2, LS1, and LS2 are manufactured by Bishop Water Technologies, ON, Canada. Effluents and attached growth media were analyzed after batch experiment; methane production, methane yield, transfer efficiencies, organic and solid removal efficiencies, pH, and attached volatile suspended solid (VSS) were measured; VSS attached to biofilms mainly correlated with the specific surface area of each biofilm. Additionally, SEM (scanning electron microscopy) was used for further understanding of biofilm formation process for BioCords and the dissimilarity in their performance. The results indicated that BioCord LS2 had positive impact on achieving higher methane production and removal efficiencies compared to other support media utilized in batch reactors. It was also demonstrated from the experiment that BioCord LS2 potentially could generate higher methane production than conventional batch bioreactor.     

Resource-dependent reproductive adjustment and the stability of consumer-resource dynamics

This study explored a consumer-resource model including reproductive and nonreproductive subpopulations of the consumer to consider whether resource-dependent reproductive adjustment by the consumer would stabilize consumer-resource dynamics. The model assumed that decreasing (increasing) resource availability caused reproductive suppression (facilitation), and that the reproductive consumer had a higher mortality rate than the nonreproductive one (i.e., a trade-off between reproduction and survival). The model predicted that the variability would be reduced when the consumer had a strong tendency to suppress reproduction in response to low resource availability or when the cost of reproduction was high, although consumer extinction became more likely. Furthermore, when the consumer-resource dynamics converged to limit cycles, reproductive adjustment enhanced the long-term average of the consumer density. It was also predicted that if reproductive suppression enhanced resource consumption efficiency (i.e., a trade-off between reproduction and foraging), then it would destabilize the system by canceling the stabilizing effect of the reproductive adjustment itself. These results suggest that it is necessary not only to identify the costs of reproduction, but also to quantify the changes in individual-level performances due to reproduction in order to understand the ecological consequences of reproductive adjustment.     

Characterization of glycerol dehydratase expressed by fusing its α- and β-subunits

The gdh and gdhr genes, encoding B₁₂-dependent glycerol dehydratase (GDH) and glycerol dehydratase reactivase (GDHR), respectively, in Klebsiella pneumoniae, were cloned and expressed in E. coli. Part of the β-subunit was lost during GDH purification when co-expressing α, β and γ subunit. This was overcome by fusing the β-subunit to α- or γ-subunit with/without the insertion of a linker peptide between the fusion moieties. The kinetic properties of the fusion enzymes were characterized and compared with wild type enzyme. The results demonstrated that the fusion protein GDHALB/C, constructed by linking the N-terminal of β-subunit to the C-terminal of α subunit through a (Gly₄Ser)₄ linker peptide, had the greatest catalytic activity. Similar to the wild-type enzyme, GDHALB/C underwent mechanism-based inactivation by glycerol during catalysis and could be reactivated by GDHR. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The transient receptor potential family of ion channels

The transient receptor potential (TRP) multigene superfamily encodes integral membrane proteins that function as ion channels. Members of this family are conserved in yeast, invertebrates and vertebrates. The TRP family is subdivided into seven subfamilies: TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), TRPA (ankyrin) and TRPN (NOMPC-like); the latter is found only in invertebrates and fish. TRP ion channels are widely expressed in many different tissues and cell types, where they are involved in diverse physiological processes, such as sensation of different stimuli or ion homeostasis. Most TRPs are non-selective cation channels, only few are highly Ca²⁺ selective, some are even permeable for highly hydrated Mg²⁺ ions. This channel family shows a variety of gating mechanisms, with modes of activation ranging from ligand binding, voltage and changes in temperature to covalent modifications of nucleophilic residues. Activated TRP channels cause depolarization of the cellular membrane, which in turn activates voltage-dependent ion channels, resulting in a change of intracellular Ca²⁺ concentration; they serve as gatekeeper for transcellular transport of several cations (such as Ca²⁺ and Mg²⁺), and are required for the function of intracellular organelles (such as endosomes and lysosomes). Because of their function as intracellular Ca²⁺ release channels, they have an important regulatory role in cellular organelles. Mutations in several TRP genes have been implicated in diverse pathological states, including neurodegenerative disorders, skeletal dysplasia, kidney disorders and pain, and ongoing research may help find new therapies for treatments of related diseases.     

Downregulation of p‐COUMAROYL ESTER 3‐HYDROXYLASE in rice leads to altered cell wall structures and improves biomass saccharification

p‐Coumaroyl ester 3‐hydroxylase (C3′H) is a key enzyme involved in the biosynthesis of lignin, a phenylpropanoid polymer that is the major constituent of secondary cell walls in vascular plants. Although the crucial role of C3′H in lignification and its manipulation to upgrade lignocellulose have been investigated in eudicots, limited information is available in monocotyledonous grass species, despite their potential as biomass feedstocks. Here we address the pronounced impacts of C3′H deficiency on the structure and properties of grass cell walls. C3′H‐knockdown lines generated via RNA interference (RNAi)‐mediated gene silencing, with about 0.5% of the residual expression levels, reached maturity and set seeds. In contrast, C3′H‐knockout rice mutants generated via CRISPR/Cas9‐mediated mutagenesis were severely dwarfed and sterile. Cell wall analysis of the mature C3′H‐knockdown RNAi lines revealed that their lignins were largely enriched in p‐hydroxyphenyl (H) units while being substantially reduced in the normally dominant guaiacyl (G) and syringyl (S) units. Interestingly, however, the enrichment of H units was limited to within the non‐acylated lignin units, with grass‐specific γ‐p‐coumaroylated lignin units remaining apparently unchanged. Suppression of C3′H also resulted in relative augmentation in tricin residues in lignin as well as a substantial reduction in wall cross‐linking ferulates. Collectively, our data demonstrate that C3′H expression is an important determinant not only of lignin content and composition but also of the degree of cell wall cross‐linking. We also demonstrated that C3′H‐suppressed rice displays enhanced biomass saccharification.     

Differences in macrobenthic faunal communities in mangrove wetland habitats (Zhanjiang,China) invaded and non-invaded by exotic cordgrass <Emphasis Type="Italic">Spartina alterniflora</Emphasis>

Mangroves are essential for maintaining local biodiversity and human well-being, and mangrove structure and functioning depend on the macrobenthos. Although exotic cordgrass, Spartina alterniflora, is an increasing threat to the mangrove wetlands (including the associated unvegetated shoals) of China, its effects on the macrobenthic fauna in such wetlands is poorly understood. The macrobenthic faunal communities were compared in (1) an Avicennia marina monoculture vs. an S. alterniflora-invaded A. marina stand (a mixture of A. marina and S. alterniflora) and in (2) an unvegetated shoal vs. an S. alterniflora-invaded shoal that had rapidly become an S. alterniflora monoculture in Zhanjiang, China. S. alterniflora invasion significantly increased plant density regardless of invaded habitat but significantly increased the contents of total carbon, organic matter, and total sulfur in the sediment only in the unvegetated shoal. The presence of S. alterniflora had little influence on indices of the macrobenthic faunal community in the A. marina monoculture, but significantly decreased the density and biomass of macrobenthic faunal community in the unvegetated shoal. These results indicate that the effects of S. alterniflora on the macrobenthic faunal community depend on which type of mangrove habitat is invaded. The composition of the macrobenthic faunal community was more similar between the invaded and non-invaded A. marina stand than between the invaded and non-invaded unvegetated shoal. Overall, the differences in the macrobenthic faunal community between invaded and non-invaded habitats were associated with increases in the sediment organic matter content and plant density.