Estimation of Endocarpon pusillum Hedwig carbon budget in the Tengger Desert based on its photosynthetic rate

This study investigated the photosynthetic rate of the lichen Endocarpon pusillum at the Chinese Academy of Sciences Shapotou Desert Research Station and estimated its annual contribution to the carbon budget in the ecosystem. The software SigmaPlot 10.0 with “Macro-Area below curves” was used to calculate the carbon fixation capacity of the lichen. The total carbon budget (ΣC) of the lichen was obtained by subtracting the respiratory carbon loss (ΣDR) from the photosynthetic carbon gain (ΣNP). Because water from precipitation plays an important role in photosynthesis in this ecosystem, the annual carbon budget of E. pusillum at the station was estimated based on the three-year average precipitation data from 2009 to 2011. Our results indicate that the lichen fixes 14.6 g C m^?2 annually. The results suggest that artificial inoculation of the crust lichen in the Tengger Desert could not only help reduce the sand and dust storms but also offer a significant carbon sink, fixing a total of 438000 t of carbon over the 30000 km² of the Tengger Desert. The carbon sink could potentially help mitigate the atmospheric greenhouse effect. Our study suggests that the carpet-like lichen E. pusillum is an excellent candidate for “Bio-carpet Engineering” of arid and semi-arid regions.     

Congruent genetic structure in the lichen-forming fungus Lobaria pulmonaria and its green-algal photobiont

The extent of codispersal of symbionts is one of the key factors shaping genetic structures of symbiotic organisms. Concordant patterns of genetic structure are expected in vertically transmitted symbioses, whereas horizontal transmission generally uncouples genetic structures unless the partners are coadapted. Here, we compared the genetic structures of mutualists, the lichen-forming fungus Lobaria pulmonaria and its primary green-algal photobiont, Dictyochloropsis reticulata. We performed analysis of molecular variance and variogram analysis to compare genetic structures between symbiosis partners. We simulated the expected number of multilocus-genotype recurrences to reveal whether the distribution of multilocus genotypes of either species was concordant with panmixia. Simulations and tests of linkage disequilibrium provided compelling evidence for the codispersal of mutualists. To test whether genotype associations between symbionts were consistent with randomness, as expected under horizontal transmission, we simulated the recurrence of fungal-algal multilocus genotype associations expected by chance. Our data showed nonrandom associations of fungal and algal genotypes. Either vertical transmission or horizontal transmission coupled with coadaptation between symbiont genotypes may have created these nonrandom associations. This study is among the first to show codispersal and highly congruent genetic structures in the partners of a lichen mutualism.     

Physiological mechanisms of adaptation of alloplasmic wheat hybrids to soil drought

We studied physiological mechanisms of plant adaptation to drought for two alloplasmic wheat (Triticum aestivum L.) hybrids (APHs) on the cytoplasm of rye (Secale cereale L.) or ovate goatgrass (Aegilops ovata L.) and two standard regionalized spring wheat cultivars, Kometa and Priokskaya. In response to plant tissue dehydration, APHs rapidly reduced the transpiration rate and lost much less water than standard cultivars. During drought, peroxidase activity was significantly increased only in APH on the rye cytoplasm, whereas it declined substantially in cv. Kometa. Peroxidation of lipids (POL) was activated in cv. Kometa stronger than in hybrids, which also indicates that, in this cultivar, there was no complete detoxification of hydrogen peroxide under stress conditions. After watering resumption, APHs displayed a better capacity for reparation than standard cultivars, which was manifested in peroxidase activation and POL suppression, i.e., in more complete reduction of the oxidative stress consequences. We concluded that a higher APH drought resistance, as compared with standard cultivars, was determined by their more efficient antioxidant defense and a better capacity for recovery.     

Frequency-based analysis of the early rapid filling pressure-flow relation elucidates diastolic efficiency mechanisms

Stiffness- and relaxation-based diastolic function (DF) assessment can characterize the presence, severity, and mechanism of dysfunction. Although frequency-based characterization of arterial function is routine (input impedance, characteristic impedance, arterial wave reflection), DF assessment via frequency-based methods incorporating optimization/efficiency criteria is lacking. By definition, optimal filling maximizes (E wave) volume and minimizes "loss" at constant stored elastic strain energy (which initiates mechanical, recoil-driven filling). In thermodynamic terms, optimal filling delivers all oscillatory power (rate of work) at the lowest harmonic. To assess early rapid filling optimization, simultaneous micromanometric left ventricular pressure and echocardiographic transmitral flow (Doppler E wave) were Fourier analyzed in 31 subjects. A validated kinematic filling model provided closed-form expressions for E wave contours and model parameters. Relaxation-based DF impairment is indicated by prolonged E wave deceleration time (DT). Optimization was assessed via regression between the dimensionless ratio of 2nd (Q2) and 3rd flow harmonics (Q3) to the lowest harmonic (Q1), i.e., (Q2/Q1) or (Q3/Q1) vs. DT or c, the filling model's viscosity/damping (energy loss) parameter. Results show that DT prolongation or increased c generated increased oscillatory power at higher harmonics (Q2/Q1 = 0.00091DT + 0.09837, r = 0.70; Q3/Q1 = 0.00053DT + 0.02747, r = 0.60; Q2/Q1 = 0.00614c + 0.15527, r = 0.91; Q3/Q1 = 0.00396c + 0.05373, r = 0.87). Because ideal filling is achieved when all oscillatory power is delivered at the lowest harmonic, the observed increase in power at higher harmonics is a measure of filling inefficiency. We conclude that frequency-based analysis facilitates assessment of filling efficiency and elucidates the mechanism by which diastolic dysfunction associated with prolonged DT impairs optimal filling.     

Relationship between the algal partners and the growth of lichen-forming fungus Porpidia crustulata

In recent years, examinations based on morphological characters and phylogenetic analyses have begun to reveal the diversity of photobionts in lichen symbioses. However, still little is known regarding genetic diversity and ecological adaptation of algal partners in lichen symbioses. In this study, we investigated the photobiont Chlorella “sp. GC” (Trebouxiophyceae), a partner of Porpidia crustulata from the Guancen Mountains, China. We examined the relationship between photobiont layer thickness and Porpidia crustulata growth over a 6-year period (2007–2012). Although Porpidia crustulata exhibited moderate growth rates (0.4–0.62 mm year^?1), photobiont layer became increasingly thinner over the six-year period. We speculate that prolonged exposure to sunlight and desiccation may deleteriously alter photobiont morphology and physiology. Porpidia crustulata may be forced into a state of physiological dormancy.     

In vivo gene expression profiling of the entomopathogenic fungus Beauveria bassiana elucidates its infection stratagems in Anopheles mosquito

The use of entomopathogenic fungi to control mosquitoes is a promising tool for reducing vector-borne disease transmission.To better understand infection stratagems of insect pathogenic fungi,we analyzed the global gene expression profiling of Beauveria bassiana at 36,60,84 and 108 h after topical infection of Anopheles stephensi adult mosquitoes using RNA sequencing(RNA-Seq).A total of 5,354 differentially expressed genes(DEGs) are identified over the course of fungal infection.When the fungus grows on the mosquito cuticle,up-regulated DEGs include adhesion-related genes involved in cuticle attachment,Pthll-like GPCRs hypothesized to be involved in host recognition,and extracellular enzymes involved in the degradation and penetration of the mosquito cuticle.Once in the mosquito hemocoel,the fungus evades mosquito immune system probably through up-regulating expression of |3-l,3-glucan degrading enzymes and chitin synthesis enzymes for remodeling of cell walls.Moreover,six previous unknown SSCP(small secreted cysteine-rich proteins) are significantly up-regulated,which may serve as "effectors" to suppress host defense responses.B.bassiana also induces large amounts of antioxidant genes to mitigate host-generated exogenous oxidative stress.At late stage of infection,B.bassiana activates a broad spectrum of genes including nutrient degrading enzymes,some transporters and metabolism pathway components,to exploit mosquito tissues and hemolymph as a nutrient source for hyphal growth.These findings establish an important framework of knowledge for further comprehensive elucidation of fungal pathogenesis and molecular mechanism of Beauveria-mosqaito interactions.     

Assessing intraspecific diversity in a lichen-forming fungus and its green algal symbiont: Evaluation of eight molecular markers

To facilitate marker selection in sequence-based studies on genetic diversity and symbiont selectivity in lichens we conducted a comparison of eight molecular markers in the lichen-forming fungus Lasallia pustulata and its trebouxioid photobiont. We compared mtSSU rDNA, mtLSU rDNA, MCM7, TSR1 (mycobiont) and nrITS rDNA, COX2, psbJ-L intergenic spacer, rbcL (photobiont) of 45 individuals from European populations of L. pustulata. Mycobiont and photobiont loci had congruent phylogenetic signals. Based on the results of this study we recommend the use of MCM7 and TSR1 (mycobiont), and nrITS rDNA and COX2 (photobiont). In this specific study system we found no sequence variability in the mycobiont loci EF1, nrITS rDNA, RPB1, and RPB2, which we sequenced for a subset of individuals. We had limited success amplifying GPD (mycobiont), actin and chloroplast LSU rDNA (photobiont), however, we do not rule out that these loci could be valuable markers in other species.     

Characterization of two novel non-reducing polyketide synthase genes from the lichen-forming fungus Hypogymnia physodes

Lichens are known to produce a variety of secondary metabolites including polyketides, which have valuable biological activities. Some polyketides are produced solely by lichens. The biosynthesis of these compounds is primarily governed by iterative type I polyketide synthases. Hypogymnia physodes synthesize polyketides such as physodic, physodalic and hydroxyphysodic acid and atranorin, which are non-reducing polyketides. Two novel non-reducing polyketide synthase (PKS) genes were isolated from a fosmid genomic library of a mycobiont of H. physodes using a 409bp fragment corresponding to part of the reductase (R) domain as a probe. H. physodes PKS1 (Hyopks1) and PKS2 (Hypopks2) contain keto synthase (KS), acyl transferase (AT), acyl carrier protein (ACP), methyl transferase (ME) and R domains. Classification based on phylogeny analysis using the translated KS and AT domains demonstrated that Hypopks1 and Hypopks2 are members of the fungal non-reducing PKSs clade III. This is the first report of non-reducing PKSs containing the R domain-mediated release mechanisms in lichens, which are also rare fungal type I PKS in non-lichenized filamentous fungi.     

Computational modeling of the EGFR network elucidates control mechanisms regulating signal dynamics

Background  

The epidermal growth factor receptor (EGFR) signaling pathway plays a key role in regulation of cellular growth and development. While highly studied, it is still not fully understood how the signal is orchestrated. One of the reasons for the complexity of this pathway is the extensive network of inter-connected components involved in the signaling. In the aim of identifying critical mechanisms controlling signal transduction we have performed extensive analysis of an executable model of the EGFR pathway using the stochastic pi-calculus as a modeling language.     

Isolation and characterization of a reducing polyketide synthase gene from the lichen-forming fungus Usnea longissima

The reducing polyketide synthases found in filamentous fungi are involved in the biosynthesis of many drugs and toxins. Lichens produce bioactive polyketides, but the roles of reducing polyketide synthases in lichens remain to be clearly elucidated. In this study, a reducing polyketide synthase gene (U1PKS3) was isolated and characterized from a cultured mycobiont of Usnea longissima. Complete sequence information regarding U1PKS3 (6,519 bp) was obtained by screening a fosmid genomic library. A U1PKS3 sequence analysis suggested that it contains features of a reducing fungal type I polyketide synthase with β-ketoacyl synthase (KS), acyltransferase (AT), dehydratase (DH), enoyl reductase (ER), ketoacyl reducatse (KR), and acyl carrier protein (ACP) domains. This domain structure was similar to the structure of ccRadsl, which is known to be involved in resorcylic acid lactone biosynthesis in Chaetomium chiversii. The results of phylogenetic analysis located U1PKS3 in the clade of reducing polyketide synthases. RT-PCR analysis results demonstrated that UIPKS3 had six intervening introns and that UIPKS3 expression was upregulated by glucose, sorbitol, inositol, and mannitol.