Brain development and predation: plastic responses depend on evolutionary history

Although the brain is known to be a very plastic organ, the effects of common ecological interactions like predation or competition on brain development have remained largely unexplored. We reared nine-spined sticklebacks (Pungitius pungitius) from two coastal marine (predation-adapted) and two isolated pond (competition-adapted) populations in a factorial experiment, manipulating perceived predatory risk and food supply to see (i) if the treatments affected brain development and (ii) if there was population differentiation in the response to treatments. We detected differences in plasticity of the bulbus olfactorius (chemosensory centre) between habitats: marine fish were not plastic, whereas pond fish had larger bulbi olfactorii in the presence of perceived predation. Marine fish had larger bulbus olfactorius overall. Irrespective of population origin, the hypothalamus was smaller in the presence of perceived predatory risk. Our results demonstrate that perceived predation risk can influence brain development, and that the effect of an environmental factor on brain development may depend on the evolutionary history of a given population in respect to this environmental factor.     

Cellulase–lignin interactions—The role of carbohydrate-binding module and pH in non-productive binding

Non-productive cellulase adsorption onto lignin is a major inhibitory mechanism preventing enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding of enzyme–lignin interactions is essential for the development of enzyme mixtures and processes for lignocellulose hydrolysis. We have studied cellulase–lignin interactions using model enzymes, Melanocarpus albomyces Cel45A endoglucanase (MaCel45A) and its fusions with native and mutated carbohydrate-binding modules (CBMs) from Trichoderma reesei Cel7A. Binding of MaCel45A to lignin was dependent on pH in the presence and absence of the CBM; at high pH, less enzyme bound to isolated lignins. Potentiometric titration of the lignin preparations showed that negatively charged groups were present in the lignin samples and that negative charge in the samples was increased with increasing pH. The results suggest that electrostatic interactions contributed to non-productive enzyme adsorption: Reduced enzyme binding at high pH was presumably due to repulsive electrostatic interactions between the enzymes and lignin. The CBM increased binding of MaCel45A to the isolated lignins only at high pH. Hydrophobic interactions are probably involved in CBM binding to lignin, because the same aromatic amino acids that are essential in CBM–cellulose interaction were also shown to contribute to lignin-binding.     

Cloning, characterization and localization of three novel class III peroxidases in lignifying xylem of Norway spruce (Picea abies)

Plant class III peroxidases (POXs) take part in the formation of lignin and maturation of plant cell walls. However, only a few examples of such peroxidases from gymnosperm tree species with highly lignified xylem tracheids have been implicated so far. We report here cDNA cloning of three xylem-expressed class III peroxidase encoding genes from Norway spruce (Picea abies). The translated proteins, PX1, PX2 and PX3, contain the conserved amino acids required for heme-binding and peroxidase catalysis. They all begin with putative secretion signal propeptide sequences but diverge substantially at phylogenetic level, grouping to two subclusters when aligned with other class III plant peroxidases. In situ hybridization analysis on expression of the three POXs in Norway spruce seedlings showed that mRNA coding for PX1 and PX2 accumulated in the cytoplasm of young, developing tracheids within the current growth ring where lignification is occurring. Function of the putative N-terminal secretion signal peptides for PX1, PX2 and PX3 was confirmed by constructing chimeric fusions with EGFP (enhanced green fluorescent protein) and expressing them in tobacco protoplasts. Full-length coding region of px1 was also heterologously expressed in Catharanthus roseus hairy root cultures. Thus, at least the spruce PX1 peroxidase is processed via the endoplasmic reticulum (ER) most likely for secretion to the cell wall. Thereby, PX1 displays correct spatiotemporal localization for participation in the maturation of the spruce tracheid secondary cell wall.     

Multiple Arabidopsis genes primed for recruitment into C₄ photosynthesis

C₄ photosynthesis occurs in the most productive crops and vegetation on the planet, and has become widespread because it allows increased rates of photosynthesis compared with the ancestral C₃ pathway. Leaves of C₄ plants typically possess complicated alterations to photosynthesis, such that its reactions are compartmented between mesophyll and bundle sheath cells. Despite its complexity, the C₄ pathway has arisen independently in 62 separate lineages of land plants, and so represents one of the most striking examples of convergent evolution known. We demonstrate that elements in untranslated regions (UTRs) of multiple genes important for C₄ photosynthesis contribute to the metabolic compartmentalization characteristic of a C₄ leaf. Either the 5′ or the 3′ UTR is sufficient for cell specificity, indicating that functional redundancy underlies this key aspect of C₄ gene expression. Furthermore, we show that orthologous PPDK and CA genes from the C₃ plant Arabidopsis thaliana are primed for recruitment into the C₄ pathway. Elements sufficient for M‐cell specificity in C₄ leaves are also present in both the 5′ and 3′ UTRs of these C₃A. thaliana genes. These data indicate functional latency within the UTRs of genes from C₃ species that have been recruited into the C₄ pathway. The repeated recruitment of pre‐existing cis‐elements in C₃ genes may have facilitated the evolution of C₄ photosynthesis. These data also highlight the importance of alterations in trans in producing a functional C₄ leaf, and so provide insight into both the evolution and molecular basis of this important type of photosynthesis.     

Inbreeding depression in perennial Lychnis viscaria (Caryophyllaceae): effects of population mating history and nutrient availability

We studied inbreeding depression in a perennial plant, Lychnis viscaria, in three populations differing in their inbreeding history and population size by measuring several traits at two nutrient levels over the plant's life cycle. The observed levels of inbreeding depression (cumulative inbreeding depression, from -0.057 to 0.629) were high for a plant with a mixed mating system. As expected, the population with a low level of isozyme variation expressed the least inbreeding depression for seed germination. Highest inbreeding depression for germination was found in the largest and genetically most variable population. No clear differences between populations in expression of inbreeding depression in the later life stages were found. The population level inbreeding depression varied with the nutrient conditions and among populations and life stages, but we found no evidence that inbreeding depression increased with lower nutrient availability. These results emphasize the importance of measuring inbreeding depression under several environmental conditions and over life stages.     

The impacts of treatment with biocontrol fungus (Phlebiopsis gigantea) on bacterial diversity in Norway spruce stumps

The biocontrol agent Phlebiopsis gigantea has been intensively applied to the surface of Picea abies stumps to control Heterobasidion root rot. But little is known about the possible impact of this treatment on the resident bacteria community in the stumps. High throughput DNA bar-coded pyrosequencing was used to characterize the diversity of bacteria in the stumps of P. abies at 1, 6 and 13 years after treatment with P. gigantea. The sequences were classified into 12 phyla and 160 genera, of which Proteobacteria and Acidobacteria were the most abundant groups over time. Moreover, at the initial stages of decay, Proteobacteria were the most abundant whereas Acidobacteria were the most common at advanced stages of decay. Treatment with P. gigantea led to significant increase of the genus Acidobacteria-Gp1 at 1 year after treatment. The analysis of observed and estimated operational taxonomic units (OTUs) as well as diversity indices revealed that P. gigantea treatment significantly decreased the initial bacterial richness in the stumps, but the bacterial community gradually recovered and the negative effects of P. gigantea was attenuated. These results provide additional insight on the risk assessment as well as environmental impact on the long-term use of P. gigantea in the control of Heterobasidion root rot in conifer forests.     

Localization of the gene for a novel human adenylyl cyclase (ADCY7) to chromosome 16

A novel form of human adenylyl cyclase (ADCY7) has been discovered in the human erythroleukemia cell line (HEL). This cell line has been widely used as a model for studies of the characteristics of human platelets. Data from HEL cells suggests that ADCY7 may be the major AC form in human platelets. In the current study polymerase chain reaction (PCR) techniques coupled with use of human/rodent somatic hybrid panels and a yeast artificial chromosome (YAC) library were used to determine the chromosomal localization of the gene (adcy7) for ADCY7 enzyme. A 251-bp product from the 3 untranslated region of human adcy7 was amplified for PCR mapping and the results localize the adcy7 gene to region 16q12–16q13 of the human genome. The AC enzyme family is characterized by the presence of 12 membrane-spanning domains in its sequences, and this chromosomal region is known to contain other genes coding for proteins characterized by 12 membrane-spanning domains.     

Colonization of a host tree by herbivorous insects under a changing climate

Climate warming has been predicted to increase the abundance of herbivorous insects. Together with concurrent poleward shifts in many insect species this may increase herbivore pressure on plants. However, the manner in which plants at higher latitudes become colonized by herbivorous insects in the future is unknown. We established a translocation experiment using 26 micropropagated silver birch Betula pendula genotypes from six populations originating from 60°N to 67°N, to study the susceptibility of the translocated birches to local herbivores. The birches were planted at three different latitudes in Finland (60°N, 62°N and 67°N). We studied the effect of source population and latitudinal translocation on herbivore density, species richness, and community composition among the genotypes growing in the same environmental conditions in two years; 2011 and 2012. The source population explained the variation in the herbivore density only in 2012, whereas latitudinal translocation did not affect herbivore density. Variation in species richness was not explained by the source population or by the latitudinal translocation. At two of the study sites, the similarity of the herbivore communities among the populations decreased with increasing latitudinal distance of the source populations, possibly because birch populations that grow geographically closer to each other are genetically more similar, and therefore support a more similar composition of the arthropod community. All birch genotypes were colonized by local herbivores, suggesting that as herbivores shift their ranges polewards, they are able to colonize novel host‐plant genotypes. This enables compositional changes in insect communities on their host plants in the future, which in turn, might affect total herbivory and eventually, plant growth.     

Plasmin activates pro-matrix metalloproteinase-2 with a membrane-type 1 matrix metalloproteinase-dependent mechanism

Membrane-type 1 matrix metalloproteinase (MT1-MMP) has been implicated as a physiological activator of progelatinase A (MMP-2). We previously reported that plasmin treatment of cells results in proMMP-2 activation and increased type IV collagen degradation. Here, we analyzed the role of MT1-MMP in plasmin activation of MMP-2 using HT-1080 cells transfected with MT1-MMP sense or antisense cDNA. Control, vector-transfected cells that expressed endogenous MT1-MMP, and antisense cDNA transfectants with very low levels of MT1-MMP did not activate proMMP-2. Conversely, cells transfected with sense MT1-MMP cDNA expressed high MT1-MMP levels and processed proMMP-2 to 68/66-kDa intermediate activation products. Control cells and MT1-MMP transfectants had much higher levels of cell-associated MMP-2 than antisense cDNA transfectants. Addition of plasmin(ogen) to control or MT1-MMP-transfected cells generated active, 62-kDa MMP-2, but was ineffective with antisense cDNA transfectants. The effect of plasmin(ogen) was prevented by inhibitors of plasmin, but not by metalloproteinase inhibitors, implicating plasmin as a mechanism for proMMP-2 activation independent of the activity of MT1-MMP or other MMPs. Plasmin-mediated activation of proMMP-2 did not result from processing of proMT1-MMP and did not correlate with alpha(v)beta(3) integrin or TIMP-2 levels. Thus, plasmin can activate proMMP-2 only in the presence of MT1-MMP; however, this process does not require the catalytic activity of MT1-MMP.