Cloning and sequencing of endochitinase genes from gliocladium virens and trichoderma species

Nucleotide sequences containing the genetic determinants of the endochitinase of Gliocladiurn virences as well as those of Trichoderma harzianum, T. hamatum, T. viride and T. pseudokoningii were determined. The ORFs of 1287 or 1293 nucleotides were interrupted by three introns. The deduced amino acid sequences of endochitinase of G. virens were highly homologous to those of Trichoderma species (82–97% identity), although the culture filtrates from G. virens showed a much stronger inhibitory effect on growth of Helicobasidium mompa than those from Trichoderma species. Phylogenic analysis showed that these sequences could be divided into three clusters regardless of genus or species.     

Testing alternative hypotheses for evolutionary diversification in an African songbird: rainforest refugia versus ecological gradients

Geographic isolation in rainforest refugia and local adaptation to ecological gradients may both be important drivers of evolutionary diversification. However, their relative importance and the underlying mechanisms of these processes remain poorly understood because few empirical studies address both putative processes in a single system. A key question is to what extent is divergence in signals that are important in mate and species recognition driven by isolation in rainforest refugia or by divergent selection across ecological gradients? We studied the little greenbul, Andropadus virens, an African songbird, in Cameroon and Uganda, to determine whether refugial isolation or ecological gradients better explain existing song variation. We then tested whether song variation attributable to refugial or ecological divergence was biologically meaningful using reciprocal playback experiments to territorial males. We found that much of the existing song variation can be explained by both geographic isolation and ecological gradients, but that divergence across the gradient, and not geographic isolation, affects male response levels. These data suggest that ecologically divergent traits, independent of historical isolation during glacial cycles, can promote reproductive isolation. Our study provides further support for the importance of ecology in explaining patterns of evolutionary diversification in ecologically diverse regions of the planet.     

Biotransformation optimization of betulin into betulinic acid production catalysed by cultured Armillaria luteo‐virens Sacc ZJUQH100‐6 cells

Aims: Betulinic acid has attracted attention in terms of its important biological and pharmacological characteristics. The main objective of this work was to optimize the variables of biotransformation process in order to enhance betulinic acid production from betulin catalysed by fungus Armillaria luteo‐virens Sacc ZJUQH100‐6. Methods and Results: Fractional factorial design and response surface methodology were applied to optimize the main parameters that affect betulinic acid production in the growing‐cells system. Results indicated that the addition of Tween 80 and substrate concentration were identified as the significant factors on betulinic acid formation, and the central composite experimental design was then adopted to derive a statistical model for optimizing biotransformation conditions. The optimum conditions were observed at pH 6·0, 0·57% Tween 80, 15 mg l^?1 betulin and at 3 days of stage of inoculation. Conclusions: Under the optimized conditions, the highest productivity of betulinic acid predicted was 9·32%, which increased by 74·53% in comparison with that of the nonoptimized. The verified experiment revealed that the model can well simulate betulin biotransformation. Moreover, the bioconversion of betulin and betulin‐28‐monooxygenase activities was compared between the optimized and the nonoptimized conditions. Significance and Impact of the Study: Current data imply that betulinic acid production from betulin can be effectively enhanced through biotransformation optimization strategy.     

Dispersal, interpatch movements, and survival in a shrubland breeding bird community

ABSTRACT Dispersal events can affect the distribution, abundance, population structure, and gene flow of animal populations, but little is known about long‐distance movements due to the difficulty of tracking individuals across space. We documented the natal and breeding dispersal of shrubland birds among 13 study sites in a 1000 km² area in southeastern Ohio. In addition, we radio‐marked and tracked 37 adult males of one shrubland specialist, the Yellow‐breasted Chat (Icteria virens). We banded 1925 juveniles and 2112 adults of nine shrubland species from 2002 to 2005. Of these, 33 (1.7%) juveniles were encountered in subsequent years (2003–2006) as adults (natal dispersal) and 442 (20.9%) birds initially banded as breeding adults were re‐encountered in subsequent years (breeding dispersal). Apparent survival of juvenile shrubland birds on their natal patches was 0.024 (95% CI 0.016–0.036). After accounting for the probability of detection, we found that 21% of birds banded as juveniles and recaptured as adults returned to their natal patches, whereas 78% of adult birds showed fidelity to the patch where they were originally captured. Moreover, natal dispersers tended to move farther than breeding dispersers (corrected natal median = 1.7 km ± 0.37; corrected breeding median = 0.23 km ± 0.10). We used our estimates of natal dispersal and annual apparent survival to estimate true survival at 0.11 (95% CI 0.07–0.18) for juveniles in their first year. However, this estimate was only applicable for birds dispersing within 7 km of their natal patches. Interpatch movements of radio‐marked Yellow‐breasted Chats were not uncommon, with 13 of 37 males located in more than one habitat patch. Overall, we observed low natal philopatry, but high adult site fidelity for shrubland birds in our study area. Considering the frequency of short‐distance movements observed (median = 531 m, range = 88–1045 m), clustering of patches within 1 km might facilitate use of shrubland habitat.     

A new formulation system for the application of biocontrol fungi to soil

A new biocontrol formulation system was devised that does not require sterile conditions during preparation. It involves mixing vermiculite and powdered wheat bran with wet or dry fermentor biomass of Trichoderma spp. or Gliocladium virens, moistening with 0.05 N HCl, and drying the mixture. Before application to soil, the preparation (VBA‐FB) is activated by re‐moistening with 0.05 N HCl and incubated at room temperature for 2–3 days to stimulate development of young hyphae of the biocontrol fungus. Populations of biocontrol fungi proliferated to greater than 10⁷ colony‐forming units (cfu) per g of soil when activated VBA‐FB was added to soil. In soil artificially infested with Rhizoctonia solani, seven isolates of the 14 studied added as VBA‐FB reduced survival and 12 reduced saprophytic growth of the pathogen. Of these, two isolates of T. hamatum (TRI‐4, Tm‐23) and one of T. harzianum (Th‐87) were the most effective. Preparations formulated with either wet or dry biomass effectively reduced pathogen survival, but activated VBA‐FB was more effective than non‐activated VBA‐FB. Storage of VBA‐FB at 25°C for 24 weeks before activation reduced viability of isolates considerably more than storage at 5°C for 24 weeks. In addition, VBA‐FB stored at 5°C before activation more effectively reduced survival of R. solani than VBA‐FB stored at 25° C. Survival of R. solani was reduced by activated VBA‐FB applied to several soil types (sandy loam, sandy clay loam, clay). Some nitrogen fertilizers increased the efficacy of VBA‐FB preparations of several isolates.     

Density independent population dynamics by Trichoderma virens in soil and defined substrates

Classical models of population dynamics predict that with increasing initial population densities the per capita growth will diminish. Observations over a broad range of initial densities with a wild-type and a genetically engineered strain of the filamentous fungus, Trichoderma virens (Arx), in soil and autoclaved soil differed from these predictions. The per capita growth response of T. virens in vitro was found to be density dependent on potato dextrose agar, but density independent on water agar. Further experiments with a defined, carbon-free medium (Vogel's medium) and, with the same medium containing sucrose, indicated that density dependent per capita growth occurred in the nutrient-rich medium but not the oligotrophic medium. This hypothesis was tested and supported experimentally through observation of density dependent per capita growth after adding nutrients to autoclaved soil. Development of better models of population dynamics will be important to predict successfully the likelihood and extent of establishment after field release of microorganims.     

The effects of food consumption rate, body size and temperature on net food conversion efficiency in saithe and whiting

Net food conversion efficiency κ was estimated from growth experiments on saithe Pollachius virens and whiting Merlangius merlangus that were fed natural prey at a range of ration levels including satiation rations. The conversion efficiency, which specifies the net energy fraction of ingested energy C , was described appropriately by a simple power function of food consumption rate as κ  = 0·272 C ^0·18 and κ  = 0·426 C ^0·11 for saithe and whiting. This functional relationship was supported by the patterns of accretion of lipids and proteins in saithe. No significant effects of temperature and body size on κ was, however, demonstrated in this study except for the indirect influence using feeding levels (rations expressed relatively to satiation rations) in bioenergetics models.     

绿木霉SM1蛋白诱导拟南芥防御反应以及激发活性氧途径研究

SM1蛋白是由绿木霉Trichoderma virens产生的一种富含半胱氨酸的小蛋白,能够作为激发子激发植物防御反应。研究了SM1蛋白对拟南芥Arabidopsis thaliana生长及诱导抗性的作用。结果表明高浓度（>10μg/mL）SM1蛋白液抑制拟南芥的生长,低浓度SM1蛋白液则不影响生长;SM1能诱导拟南芥对细菌性叶斑病Pseudomonas syringae pv. tomato DC3000的抗性,引起拟南芥叶片过氧化氢的积累。SM1蛋白处理后,拟南芥叶片中植物防御反应相关基因PDF1.2、LOX2和活性氧酶基因 SOD、POD等表达显著上升,说明SM1在激活植物的JA/ET和ROS途径中发挥着重要作用。研究为进一步研究SM1诱导植物抗性的机理提供了基础。     

Hydroxylation of the triterpenoid nigranoic acid by the fungus Gliocladium roseum YMF1.00133

The ability of the fungus Gliocladium roseum YMF1.00133 to transform the bioactive nigranoic acid (=(24Z)-9,19-cyclo-3,4-secolanosta-4(28),24-diene-3,26-dioic acid) was investigated. Three new products from the co-cultures of nigranoic acid and G. roseum YMF1.00133 were obtained by employing a combination of Sephadex LH-20 and silica-gel column chromatography. The major metabolite was identified as 15beta-hydroxynigranoic acid, and the minor metabolites as 6alpha,15beta-dihydroxynigranoic acid and 7beta,15beta-dihydroxynigranoic acid by mass spectrometry and NMR spectroscopy. This is the first report of the biotransformation of the A-ring-secocycloartene triterpenoid, nigranoic acid.     

Screening of cellulase-free fungal xylanases and evaluation of their performance on sulfite dissolving pulp

Cellulase-free xylanase preparations of different fungal origin lowered the xylan content of acid sulfite dissolving pulp from 5% (w/v) to less than 4%. This was not, though, related to the amount of reducing sugars released. The pulp bleachability improved in samples where xylan had been mostly degraded, however, the increment in brightness declined (from 2.0–2.9 to 1.0–1.2 brightness points) when the subsequent number of chemical bleaching steps increased from 1 to 5.