PROTON GRADIENT REGULATION5 Is Essential for Proper Acclimation of Arabidopsis Photosystem I to Naturally and Artificially Fluctuating Light Conditions

In nature, plants are challenged by constantly changing light conditions. To reveal the molecular mechanisms behind acclimation to sometimes drastic and frequent changes in light intensity, we grew Arabidopsis thaliana under fluctuating light conditions, in which the low light periods were repeatedly interrupted with high light peaks. Such conditions had only marginal effect on photosystem II but induced damage to photosystem I (PSI), the damage being most severe during the early developmental stages. We showed that PROTON GRADIENT REGULATION5 (PGR5)-dependent regulation of electron transfer and proton motive force is crucial for protection of PSI against photodamage, which occurred particularly during the high light phases of fluctuating light cycles. Contrary to PGR5, the NAD(P)H dehydrogenase complex, which mediates cyclic electron flow around PSI, did not contribute to acclimation of the photosynthetic apparatus, particularly PSI, to rapidly changing light intensities. Likewise, the Arabidopsis pgr5 mutant exhibited a significantly higher mortality rate compared with the wild type under outdoor field conditions. This shows not only that regulation of PSI under natural growth conditions is crucial but also the importance of PGR5 in PSI protection.     

Distribution and Metabolic Diversity of Microorganisms in Deep Igneous Rock Aquifers of Finland

Groundwater samples from 200- to 950-m depths in four igneous rock sites in Finland were investigated for different metabolic groups of microorganisms, and the data were compared with the available geochemical record. Samples were collected with a pressurized groundwater sampling system developed for gas and microbiological sampling. Two of the sites had groundwater that was fresh, with < 0.2 g/l dissolved solids, whereas that at the two other sites was much more saline, reaching a maximum of 24 g/l dissolved solids. The groundwater contained gases, 33 to 340 ml/l, with nitrogen or methane dominating. Total cell numbers were 10 5 to 10 6 cells/ml, which is typical for deep igneous rock aquifers. Growth media were designed to mimic the actual groundwater chemistry at each sampling point and used for most probable number enumeration of methanogens, acetogens, sulfate-reducing bacteria (SRB), and iron-reducing bacteria (IRB). SRB predominated in sites where iron sulfide fracture-filling minerals are common. IRB were the main population in one site where iron sulfide fracture minerals are not present, but iron hydroxide fracture minerals predominate. Fracture-filling minerals were a better indicator of microbial populations than was groundwater chemistry. Low numbers of autotrophic methanogens were cultured. One of several possible interpretations of stable isotope data suggested that most of the detected methane is thermogenic, which would correlate with few active methanogens. However, we concluded other interpretations were also possible.     

Mycological records from ISAM 9, Kevo,Finland

ISAM 9 (International Symposium of Arctic-Alpine Mycology) was held in August 2012?at the Kevo Lapland Research Station in Utsjoki in northernmost Finnish Lapland. In addition to Utsjoki, some excursions were made in Finnmark, the northernmost part of Norway. Kevo station lies in the subarctic zone characterized by mountain birch (Betula pubescens var. czerepanovii), but the fells reach the arctic tundra zone. Áilegas fells at Utsjoki village and at Nuvvus lie on acid ground as does Skalluvaara, and all are under influence of reindeer grazing. The Gistuskaidi fell is highest and is characterized by the presence of more basic rocks; the vegetation also reflects some amount of maritime influence. The places visited on the Norwegian side belong to the Nesseby commune at the sea shore and Tana commune on the shore of the Tana River and along the road to Båtsfjord where the tundra is maritime and mossy with calcareous spots. In all 123 taxa were found during the excursions, some of them not determined at species level. The reported fungal taxa belong to the Basidiomycota (115 taxa), Ascomycota (7 taxa), and Mycetozoa (1 taxon).     

Proprotein Convertase Subtilisin/Kexin Type 7 (PCSK7) Is Essential for the Zebrafish Development and Bioavailability of Transforming Growth Factor β1a (TGFβ1a)

Proprotein convertase subtilisin/kexin (PCSK) enzymes convert proproteins into bioactive end products. Although other PCSK enzymes are known to be essential for biological processes ranging from cholesterol metabolism to host defense, the in vivo importance of the evolutionarily ancient PCSK7 has remained enigmatic. Here, we quantified the expressions of all pcsk genes during the 1st week of fish development and in several tissues. pcsk7 expression was ubiquitous and evident already during the early development. To compare mammalian and zebrafish PCSK7, we prepared homology models, which demonstrated remarkable structural conservation. When the PCSK7 function in developing larvae was inhibited, we found that PCSK7-deficient fish have defects in various organs, including the brain, eye, and otic vesicle, and these result in mortality within 7 days postfertilization. A genome-wide analysis of PCSK7-dependent gene expression showed that, in addition to developmental processes, several immune system-related pathways are also regulated by PCSK7. Specifically, the PCSK7 contributed to the mRNA expression and proteolytic cleavage of the cytokine TGFβ1a. Consequently, tgfβ1a morphant fish displayed phenotypical similarities with pcsk7 morphants, underscoring the importance of this cytokine in the zebrafish development. Targeting PCSK activity has emerged as a strategy for treating human diseases. Our results suggest that inhibiting PCSK7 might interfere with normal vertebrate development.     

Transcriptome Analysis Reveals Signature of Adaptation to Landscape Fragmentation

We characterize allelic and gene expression variation between populations of the Glanville fritillary butterfly (Melitaea cinxia) from two fragmented and two continuous landscapes in northern Europe. The populations exhibit significant differences in their life history traits, e.g. butterflies from fragmented landscapes have higher flight metabolic rate and dispersal rate in the field, and higher larval growth rate, than butterflies from continuous landscapes. In fragmented landscapes, local populations are small and have a high risk of local extinction, and hence the long-term persistence at the landscape level is based on frequent re-colonization of vacant habitat patches, which is predicted to select for increased dispersal rate. Using RNA-seq data and a common garden experiment, we found that a large number of genes (1,841) were differentially expressed between the landscape types. Hexamerin genes, the expression of which has previously been shown to have high heritability and which correlate strongly with larval development time in the Glanville fritillary, had higher expression in fragmented than continuous landscapes. Genes that were more highly expressed in butterflies from newly-established than old local populations within a fragmented landscape were also more highly expressed, at the landscape level, in fragmented than continuous landscapes. This result suggests that recurrent extinctions and re-colonizations in fragmented landscapes select a for specific expression profile. Genes that were significantly up-regulated following an experimental flight treatment had higher basal expression in fragmented landscapes, indicating that these butterflies are genetically primed for frequent flight. Active flight causes oxidative stress, but butterflies from fragmented landscapes were more tolerant of hypoxia. We conclude that differences in gene expression between the landscape types reflect genomic adaptations to landscape fragmentation.     

Temperature and soil fertility as regulators of tree line Scots pine growth and survival—implications for the acclimation capacity of northern populations

The acclimation capacity of leading edge tree populations is crucially important in a warming climate. Theoretical considerations suggest that adaptation through genetic change is needed, but this may be a slow process. Both positive and catastrophic outcomes have been predicted, while empirical studies have lagged behind theory development. Here we present results of a 30‐year study of 55,000 Scots pine (Pinus sylvestris) trees, planted in 15 common gardens in three consecutive years near and beyond the present Scots pine tree line. Our results show that, contrary to earlier predictions, even long‐distance transfers to the North can be successful when soil fertility is high. This suggests that present northern populations have a very high acclimation capacity. We also found that while temperature largely controls Scots pine growth, soil nutrient availability plays an important role—in concert with interpopulation genetic variation—in Scots pine survival and fitness in tree line conditions. These results suggest that rapid range expansions and substantial growth enhancements of Scots pine are possible in fertile sites as seed production and soil nutrient mineralization are both known to increase under a warming climate. Finally, as the ontogenetic pattern of tree mortality was highly site specific and unpredictable, our results emphasize the need for long‐term field trials when searching for the factors that control fitness of trees in the variable edaphic and climatic conditions of the far North.     

Iodinated melatonin: preparation and characterization of the molecular structure by mass and 1H NMR spectroscopy

Synthetic melatonin was iodinated by treatment with potassium iodide in the presence of an oxidizing agent, Iodo-Gen. The iodination products of melatonin were extracted with chloroform and separated by HPLC. The fraction showing immunoreactivity with respect to melatonin antisera was characterized as iodomelatonin by mass spectrometry, so that the substitution of iodine had occurred at a ring carbon atom. 1H NMR spectra showed the iodine to be incorporated at the C-2 position of the indole moiety. The N-[2-(2-iodo-5-methoxy-1H-indol-3-yl)ethyl]acetamide (2-iodomelatonin) reported here is more useful than [3H]melatonin as a tracer in melatonin radioimmunoassay. This method offers also the possibility of preparing iodinated serotonin and other indoleamines for biological studies.