Microbial hydroxylation of progesterone with Acremonium strictum

Microbial hydroxylation of progesterone occurred in the culture of Acremonium strictum PTCC 5282 to produce two hydroxylated pregnene-like steroids. The metabolites were purified and characterized using spectroscopic methods and identified as 15alpha-hydroxyprogesterone and 15alpha-hydroxydeoxycorticosterone.     

Purification and partial characterization of a phytotoxin produced by sarocladium oryzae,the rice sheath rot pathogen: Reinigung und partielle charakterisierung eines vom reisblattscheidenfäule-pathogen sarocladium oryzae erzeugten phytotoxins

An extracellular, hydrophilic, thermostable phytotoxin was purified to homogeneity from culture fluids of Sarocladium oryzae and sheath rot infected rice plants. The phytotoxin was purified by solvent extraction, gel filtration on Sephadex G-75 and HPLC. Toxicity was evaluated with detached leaf sheath and electrolyte leakage bioassays. Purified phytotoxin induced visible symptoms of the disease, when applied to rice sheath even at a low concentration of 5?μg. The toxin is a glycoprotein with carbohydrate as major component. The importances of the carbohydrate moiety for toxic activity was indicated by inactivation of toxic compound after periodate oxidation. The toxin caused lesions on a number of other monocots and dicots and proved to be non-host specific. This is the first report of the purification and characterization of S. oryzae toxin from in vitro and in vivo and we propose its name SO-toxin.     

Altered substrate specificity of the gluco‐oligosaccharide oxidase from Acremonium strictum

A gluco‐oligosaccharide oxidase (GOOX) from Acremonium strictum type strain CBS 346.70 was cloned and expressed in Pichia pastoris. The recombinant protein, GOOX‐VN, contained fifteen amino acid substitutions compared with the previously reported A. strictum GOOX. These two enzymes share 97% sequence identity; however, only GOOX‐VN oxidized xylose, galactose, and N‐acetylglucosamine. Besides monosaccharides, GOOX‐VN oxidized xylo‐oligosaccharides, including xylobiose and xylotriose with similar catalytic efficiency as for cello‐oligosaccharides. Of three mutant enzymes that were created in GOOX‐VN to improve substrate specificity, Y300A and Y300N doubled k_cat values for monosaccharide and oligosaccharide substrates. With this novel substrate specificity, GOOX‐VN and its variants are particularly valuable for oxidative modification of cello‐ and xylo‐oligosaccharides. Biotechnol. Bioeng. 2011;108: 2261–2269. © 2011 Wiley Periodicals, Inc.     

Relationship between acid phosphatase activity and P concentration in organs of Cyclopia and Aspalathus species,and a non-legume of the Cape Floristic Region

Aims The role of tissue acid phosphatase (APase) activity of legumes and non-legumes in their P nutrition and adaptation to low-P soils is not well understood. To better understand this, a relationship between APase activity and P concentration in leaves, stems, roots and nodules of legumes,CyclopiaandAspalathusand a non-legume,Leucadendron strictum, all native to the P-poor soils of the Cape fynbos biome, was assessed.     

Fungal endophyte diversity from tropical forage grass Brachiaria

ABSTRACT

Background

Microbial endophytes can be beneficial to host plants, improving resistance against biotic and abiotic stress. While beneficial fungal endophytes have been well characterised in temperate grasses, knowledge about fungal endophytes of tropical grasses is limited.     

Fluorescent pseudomonad mixtures mediate disease resistance in rice plants against sheath rot (<Emphasis Type="Italic">Sarocladium oryzae</Emphasis>) disease

Plant growth-promoting rhizobacterial (PGPR) strains were isolated from different agro-ecosystems of Tamil Nadu, India, and were tested for their efficacy against the sheath rot pathogen Sarocladium oryzae under in vitro, glasshouse and field conditions. Vigour and a relative performance index (RPI) were used to assay the growth promotion and antagonistic activity of Pseudomonas strains against S. oryzae under in vitro conditions. The results revealed the significant performance by strains Pf1, TDK1 and PY15 compared to other strains. Further, the combination of Pseudomonas strains Pf1, TDK1 and PY15 was more effective in reducing sheath rot disease in rice plants compared to individual strains under glasshouse and field conditions. Quantitative and native polyacrylamide gel electrophoresis (PAGE) analysis of peroxidase (PO), polyphenol oxidase (PPO) and chitinase activity in rice plants showed an increased accumulation of defence enzymes in the treatment with a combination of Pf1, TDK1 and PY15 compared to the treatment with individual strains and untreated controls. The present study revealed the probable influence of antagonism, plant growth promotion and induced systemic resistance (ISR) by the mixture of Pseudomonas bioformulations in enhancing the disease resistance in rice plants against sheath rot disease.

Fungal endophyte negative effects on herbivory are enhanced on intact plants and maintained in a subsequent generation

1. Fungal endophytes are ubiquitous associates of virtually all plant species. Although many studies have focused on the role of these microorganisms as mediators of plant–herbivore interactions, these studies have usually been conducted using short‐term experiments. 2. Truly effective defences against herbivores may require normal functioning of the plant, as excised leaves may be less resistant as compared with those still attached to the plant. Yet, most studies investigating possible effects of endophytes in conferring host resistance to herbivores have been conducted with plant parts rather than intact plants. 3. Using the root endophytic fungus (Acremonium strictum)—broad bean (Vicia faba)—generalist herbivore (Helicoverpa armigera) model, we conducted experiments to examine whether endophyte effects on herbivory would depend on the experimental setting used in the investigation and whether they would translate into a subsequent generation of the herbivore. 4. Acremonium strictum negative effects on the fitness of H. armigera first generation were more evident when the larvae foraged freely on inoculated intact whole plants than when offered leaf discs of inoculated plants. Furthermore, these effects were carried over into H. armigera second generation reared on an artificial diet. 5. Acremonium strictum could not be re‐isolated from V. faba leaves; hence direct contact between the endophyte and the insect could be excluded. Alternatively, loss of volatiles or inhibitory effects of compounds that were stronger in situ might have caused changes in larval feeding and performance on leaf discs as compared with intact plants, regardless of infection status. 6. We suggest that the reduction in fitness parameters of H. armigera across two generations is caused indirectly via an endophyte‐triggered reduction in plant quality.     

Interaction between a fungal endophyte and root herbivores of Ammophila arenaria

The effect of an endophytic fungus (Acremonium strictum) on plant-growth related parameters of marram grass (Ammophila arenaria), and its potential as a protective agent against root herbivores (Pratylenchus dunensis and Pratylenchus penetrans, root-lesion nematodes) was investigated in two inoculation experiments under different conditions. Acremonium strictum-inoculated plants showed increased plant development in terms of root biomass in the first experiment and increased number of tillers in the second experiment and biomass was less suppressed by nematodes than the Acremonium strictum-free plants. In neither experiment did Acremonium strictum reduce multiplication of root herbivores. On the contrary, Acremonium strictum-inoculated plants seemed to increase herbivore multiplication. Plants infected with P. penetrans benefitted more from the endophytic fungus than those with P. dunensis in terms of total biomass. The effect of Acremonium strictum on interspecific competition was also analyzed by plant inoculation with both nematode species. In Acremonium strictum-free plants with mixed nematode inoculum, the total number of nematodes, compared to numbers observed in one-species inoculation, was less than expected, suggesting that interspecific competition took place. In Acremonium strictum-inoculated plants no interspecific competition was observed. Plants inoculated with P. dunensis, P. penetrans and Acremonium strictum showed decreased total biomass compared to Acremonium strictum-free plants inoculated with the same nematodes. The implications of increased tillering and root growth of plants with Acremonium endophytes are discussed in relation to the sand stabilizing role of Ammophila arenaria in coastal dunes.     

Origin and genetic structure of feral rye in the western United States

Feral rye (Secale cereale) is a serious, introduced weed of dry land agricultural regions of the western United States. It closely resembles cultivated cereal rye (Secale cereale cereale L.) with the exception of having a shattering seed head. Feral rye may have originated from hybridization of cultivated rye with mountain rye, Secale strictum, as past studies of northern Californian populations suggest, or directly from volunteer cultivated rye. We characterized the genetic structure of feral rye populations across a broad geographical range and reexamined evidence for hybrid origin versus direct evolution from domesticated cultivars. Eighteen feral populations were examined from three climatically distinct regions in the western United States. Seven cultivars, four mountain rye accessions, and one wild annual relative (Secale cereale ancestrale) were included in our analysis as possible progenitors of feral rye. Individual plants were scored for 14 allozyme and three microsatellite loci. Estimates of genetic diversity in feral populations were relatively high compared to those of the possible progenitors, suggesting that the weed had not undergone a genetic bottleneck. Weed populations had no geographical structure at either a broad or a local scale, suggesting idiosyncratic colonization and gene-flow histories at each site. Feral rye populations were no more closely related to mountain rye than cultivars were. They were, however, weakly clustered as a distinct lineage relative to cultivars. Our results do not support an interspecific hybrid origin for feral rye, but do suggest that the sampled populations of feral rye share a common ancestry that may explain its weedy nature.