Functional redundancy between flavodiiron proteins and NDH‐1 in Synechocystis sp. PCC 6803

In oxygenic photosynthetic organisms, excluding angiosperms, flavodiiron proteins (FDPs) catalyze light‐dependent reduction of O₂ to H₂O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. In Synechocystis sp. PCC 6803, four FDP isoforms function as hetero‐oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase‐like complex (NDH‐1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH‐1 types have been characterized in cyanobacteria: NDH‐1₁ and NDH‐1₂, which function in respiration; and NDH‐1₃ and NDH‐1₄, which function in CO₂ uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants (?flv1 and Δflv3) and the double NDH‐1 mutants (?d1d2, which is deficient in NDH‐1_1,2 and ?d3d4, which is deficient in NDH‐1_3,4), we studied triple mutants lacking one of Flv1 or Flv3, and NDH‐1_1,2 or NDH‐1_3,4. We show that the presence of either Flv1/3 or NDH‐1_1,2, but not NDH‐1_3,4, is indispensable for survival during changes in growth conditions from high CO₂/moderate light to low CO₂/high light. Our results show functional redundancy between FDPs and NDH‐1_1,2 under the studied conditions. We suggest that ferredoxin probably functions as a primary electron donor to both Flv1/3 and NDH‐1_1,2, allowing their functions to be dynamically coordinated for efficient oxidation of photosystem I and for photoprotection under variable CO₂ and light availability.     

An Abscisic Acid-Independent Oxylipin Pathway Controls Stomatal Closure and Immune Defense in Arabidopsis

Plant stomata function in innate immunity against bacterial invasion and abscisic acid (ABA) has been suggested to regulate this process. Using genetic, biochemical, and pharmacological approaches, we demonstrate that (i) the Arabidopsis thaliana nine-specific-lipoxygenase encoding gene, LOX1, which is expressed in guard cells, is required to trigger stomatal closure in response to both bacteria and the pathogen-associated molecular pattern flagellin peptide flg22; (ii) LOX1 participates in stomatal defense; (iii) polyunsaturated fatty acids, the LOX substrates, trigger stomatal closure; (iv) the LOX products, fatty acid hydroperoxides, or reactive electrophile oxylipins induce stomatal closure; and (v) the flg22-mediated stomatal closure is conveyed by both LOX1 and the mitogen-activated protein kinases MPK3 and MPK6 and involves salicylic acid whereas the ABA-induced process depends on the protein kinases OST1, MPK9, or MPK12. Finally, we show that the oxylipin and the ABA pathways converge at the level of the anion channel SLAC1 to regulate stomatal closure. Collectively, our results demonstrate that early biotic signaling in guard cells is an ABA-independent process revealing a novel function of LOX1-dependent stomatal pathway in plant immunity.     

Visual Interactions Conform to Pattern Decorrelation in Multiple Cortical Areas

Neural responses to visual stimuli are strongest in the classical receptive field, but they are also modulated by stimuli in a much wider region. In the primary visual cortex, physiological data and models suggest that such contextual modulation is mediated by recurrent interactions between cortical areas. Outside the primary visual cortex, imaging data has shown qualitatively similar interactions. However, whether the mechanisms underlying these effects are similar in different areas has remained unclear. Here, we found that the blood oxygenation level dependent (BOLD) signal spreads over considerable cortical distances in the primary visual cortex, further than the classical receptive field. This indicates that the synaptic activity induced by a given stimulus occurs in a surprisingly extensive network. Correspondingly, we found suppressive and facilitative interactions far from the maximum retinotopic response. Next, we characterized the relationship between contextual modulation and correlation between two spatial activation patterns. Regardless of the functional area or retinotopic eccentricity, higher correlation between the center and surround response patterns was associated with stronger suppressive interaction. In individual voxels, suppressive interaction was predominant when the center and surround stimuli produced BOLD signals with the same sign. Facilitative interaction dominated in the voxels with opposite BOLD signal signs. Our data was in unison with recently published cortical decorrelation model, and was validated against alternative models, separately in different eccentricities and functional areas. Our study provides evidence that spatial interactions among neural populations involve decorrelation of macroscopic neural activation patterns, and suggests that the basic design of the cerebral cortex houses a robust decorrelation mechanism for afferent synaptic input.     

Microfragmentation concept explains non-positive environmental heterogeneity–diversity relationships

Although recent studies have revealed that the relationship between diversity and environmental heterogeneity is not always positive, as classical niche theory predicts, scientists have had difficulty interpreting these results from an ecological perspective. We propose a new concept—microfragmentation—to explain how small-scale heterogeneity can have neutral or even negative effect on species diversity. We define microfragmentation as a community level process of splitting habitat into a more heterogeneous environment that can have non-positive effects on the diversity through habitat loss and subsequent isolation. We provide support for the microfragmentation concept with results from spatially explicit heterogeneity–diversity model simulations, in which varying sets of species (with different ratios of specialist and generalist species) were modeled at different levels of configurational heterogeneity (meaning that only the habitat structure was changed, not its composition). Our results indicate that environmental heterogeneity can affect community diversity in the same way as fragmentation at the landscape level. Although generalist species might not be seriously affected by microfragmentation, the persistence of specialist species can be seriously disturbed by small-scale patchiness. The microfragmentation concept provides new insight into community level diversity dynamics and can influence conservation and management strategies.     

Vegetation structure and photosynthesis respond rapidly to restoration in young coastal fens

Young coastal fens are rare ecosystems in the first stages of peatland succession. Their drainage compromises their successional development toward future carbon (C) reservoirs. We present the first study on the success of hydrological restoration of young fens. We carried out vegetation surveys at six young fens that represent undrained, drained, and restored management categories in the Finnish land uplift coast before and after restoration. We measured plant level carbon dioxide (CO₂) assimilation and chlorophyll fluorescence (Fv/Fm) from 17 most common plant species present at the sites. Within 5 years of restoration, the vegetation composition of restored sites had started to move toward the undrained baseline. The cover of sedges increased the most in response to restoration, while the cover of deciduous shrubs decreased the most. The rapid response indicates high resilience and low resistance of young fen ecosystems toward changes in hydrology. Forbs had higher photosynthetic and respiration rates than sedges, deciduous shrubs, and grasses, whereas rates were lowest for evergreen shrubs and mosses. The impact of management category on CO₂ assimilation was an indirect consequence that occurred through changes in plant species composition: Increase in sedge cover following restoration also increased the potential photosynthetic capacity of the ecosystem. Synthesis and applications. Restoration of forestry drained young fens is a promising method for safeguarding them and bringing back their function as C reservoirs. However, their low resistance to water table draw down introduces a risk that regeneration may be partially hindered by the heavy drainage in the surrounding landscape. Therefore, restoration success is best safeguarded by managing the whole catchments instead of carrying out small‐scale projects.     

Study of involvement of ImuB and DnaE2 in stationary-phase mutagenesis in Pseudomonas putida

Several bacterial species carry in their genomes a so-called "mutagenesis" gene cluster encoding ImuB which is similar to Y-family DNA polymerases, and DnaE2 related to the catalytic subunit DnaE of Pol III. Y-family DNA polymerases are known to be involved in stationary-phase mutagenesis and DnaE2 homologues characterized so far have expressed a mutator phenotype. In this study, we raised a question about the involvement of ImuB and DnaE2 in stationary-phase mutagenesis. Here, we show that Pseudomonas putida ImuB and DnaE2 have antagonistic effects on stationary-phase mutagenesis. ImuB facilitated accumulation of stationary-phase mutants up to two-fold. In contrast to that, DnaE2 had no significant effect on emergence of 1-bp deletion mutants and moreover, it acted as an anti-mutator in accumulation of base substitution mutants in starving bacteria. Similar antagonistic effects of DnaE2 and ImuB on mutagenesis appeared also in UV-mutagenesis study. This data distinguishes the DnaE2 of P. putida from its homologues studied in other organisms.     

Substrate specificity of the pseudouridine synthase RluD in Escherichia coli

Pseudouridine synthase RluD converts uridines at positions 1911, 1915, and 1917 of 23S rRNA to pseudouridines. These nucleotides are located in the functionally important helix-loop 69 of 23S rRNA. RluD is the only pseudouridine synthase that is required for normal growth in Escherichia coli. We have analyzed substrate specificity of RluD in vivo. Mutational analyses have revealed: (a) RluD isomerizes uridine in vivo only at positions 1911, 1915, and 1917, regardless of the presence of uridine at other positions in the loop of helix 69 of 23S rRNA variants; (b) substitution of one U by C has no effect on the conversion of others (i.e. formation of pseudouridines at positions 1911, 1915, and 1917 are independent of each other); (c) A1916 is the only position in the loop of helix 69, where mutations affect the RluD specific pseudouridine formation. Pseudouridines were determined in the ribosomal particles from a ribosomal large subunit defective strain (RNA helicase DeaD(-)). An absence of pseudouridines in the assembly precursor particles suggests that RluD directed isomerization of uridines occurs as a late step during the assembly of the large ribosomal subunit.     

Effects of electromagnetic field emitted by cellular phones on the EEG during an auditory memory task: a double blind replication study

The effects of electromagnetic fields (EMF) emitted by cellular phones on the event related desynchronization/synchronization (ERD/ERS) of the 4-6, 6-8, 8-10, and 10-12 Hz electroencephalogram (EEG) frequency bands were studied in 24 normal subjects performing an auditory memory task. This study was a systematic replication of our previous work. In the present double blind study, all subjects performed the memory task both with and without exposure to a digital 902 MHz field in a counterbalanced order. We were not able to replicate the findings from our earlier study. All eight of the significant changes in our earlier study were not significant in the present double blind replication. Also, the effect of EMF on the number of incorrect answers in the memory task was inconsistent. We previously reported no significant effect of EMF exposure on the number of incorrect answers in the memory task, but a significant increase in errors was observed in the present study. We conclude that EMF effects on the EEG and on the performance on memory tasks may be variable and not easily replicable for unknown reasons.     

Proteomic analysis of aneuploid lines in the homeologous group 1 of the hexaploid wheat cultivar Courtot

Three monosomic lines (MSLs) and three nullisomic lines (NSLs) of the homeologous group 1 and one euploid line of the bread wheat Triticum aestivum cultivar Courtot were used in a proteomic approach to investigate the effects of zero, one or two doses of chromosomes 1A, 1B and 1D on the amount of endosperm proteins. Polypeptides whose amounts changed significantly between each aneuploid line and the euploid line were identified using image analyses of two-dimensional gel electrophoresis patterns resulting from specific endosperm protein extractions. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry and electrospray ionization tandem mass spectrometry were also used for protein identification. Removing one chromosome or a chromosome pair allowed varying responses to be observed for the remaining endosperm protein genes. Compensation phenomena for the high molecular weight glutenin subunits (HMW-GS) were detected only in the MSLs. Subunits Bx7, By8 and Dy12 were the only HMW-GS overexpressed (from 152-737%) when chromosomes 1A or 1B or 1D were at hemizygous state. Thirteen new protein spots were detected only in the NSL1D, and seven were identified as HMW-GS analogs. These seven new spots may result from the expression of inactive genes. The HMW-GS were of significantly higher volume in MSLs, whereas the low molecular weight glutenin subunits and the gamma-gliadins were of lower volume in aneuploid lines. Most of the down-regulated proteins in the MSLs were storage proteins encoded at loci located on another chromosome pair. Complex regulations between chromosomes and loci of the homeologous groups 1 and 6 in bread wheat are discussed.