The transcription factor γMYB2 acts as a negative regulator of secondary cell wall thickening in anther and stem

Secondary cell wall (SCW) thickening provides the mechanical force for anther dehiscence and plays an important role in the formation of xylem structure. We have previously reported that γMYB2, a MYB coiled-coil protein, directly binds to the P1BS cis-element of the PLA₂-γ promoter and acts as a co-activator of γMYB1 in controlling the expression of PLA₂-γ. In this study, we analyzed morphological phenotypes of the constitutive overexpression (γMYB2-OE) and knock-down (γMYB2-KD) lines of γMYB2. We found that γMYB2 overexpression caused the collapse of the endothecium layer, thereby suppressing anther dehiscence and forming short infertile siliques. The γMYB2-OE also showed less cellulose deposition in the xylem and had a longer primary stem than the wild-type, while γMYB2-KD had greater cellulose accumulation and a shorter primary stem than the wild-type. We demonstrated that the male sterility and the longer primary stem in γMYB2-OE were caused by reduced expression of SCW thickening-related genes. Our results suggest that γMYB2 acts as a negative regulator in controlling the SCW thickening in Arabidopsis.

siAbasic: a comprehensive database for potent siRNA-6Ø sequences without off-target effects

Small interfering RNA (siRNA) is widely used to specifically silence target gene expression, but its microRNA (miRNA)-like function inevitably suppresses hundreds of off-targets. Recently, complete elimination of the off-target repression has been achieved by introducing an abasic nucleotide to the pivot (position 6; siRNA-6Ø), of which impaired base pairing destabilizes transitional nucleation (positions 2–6). However, siRNA-6Ø varied in its conservation of on-target activity (∼80–100%), demanding bioinformatics to discover the principles underlying its on-target efficiency. Analyses of miRNA–target interactions (Ago HITS-CLIP) showed that the stability of transitional nucleation correlated with the target affinity of RNA interference. Furthermore, interrogated analyses of siRNA screening efficiency, experimental data and broadly conserved miRNA sequences showed that the free energy of transitional nucleation (positions 2–5) in siRNA-6Ø required the range of stability for effective on-target activity (−6 ≤ ΔG[2:5] ≤ −3.5 kcal mol⁻¹). Taking into consideration of these features together with locations, guanine-cytosine content (GC content), nucleotide stretches, single nucleotide polymorphisms and repetitive elements, we implemented a database named ‘siAbasic’ that provided the list of potent siRNA-6Ø sequences for most of human and mouse genes (≥ ∼95%), wherein we experimentally validated some of their therapeutic potency. siAbasic will aid to ensure potency of siRNA-6Ø sequences without concerning off-target effects for experimental and clinical purposes.

First Report of Cobweb Disease Caused by Cladobotryum mycophilum on the Edible Mushroom Pleurotus eryngii in Korea

Pleurotus eryngii is one of the most commercially important mushrooms in Korea. In May 2009, unusual symptoms were observed in P. eryngii grown in mushroom farms in Changnyeong and Hapcheon, in Gyeong-nam Province, Korea. One of the main symptoms was cobweb-like growth of fungal mycelia over the mushroom surface. Colonies on the surface rapidly overwhelmed the mushrooms, which turned pale brown or yellow. Mushrooms eventually turned dark brown and became rotten. Colonies of the isolates on potato dextrose agar (PDA) were yellowish, and a reddish or orange color was evident in the agar. The colonies grew 20 to 30 mm per day on PDA. Large spores with a single septum were produced on vertically branched conidiophores bearing two to four, mostly three to four, sporogenous cells, ranging from 17.2 to 20.5 μm long and 8.0 to 10.2 μm thick. The shape of the conidia was ellipsoid and obovoid. These morphological characteristics are consistent with descriptions of Cladobotryum mycophilum, a causal agent of cobweb disease in Agaricus bisporus (1,4). To identify the isolated fungal pathogen, the ITS region was amplified with ITS1 and ITS4 primers and sequenced. The sequence data from the isolate was deposited in GenBank (Accession No. JF693809). A BLAST search showed that the isolated strain belonged to a species of Cladobotryum. The highest similarity (99.5%) was to the ITS sequence of C. mycophilum (teleomorph Hypomyces odoratus) (GenBank Accession Nos. JF505112 and Y17096) (3,4). The strain that was tested for pathogenicity was grown on PDA at 25°C for 72 h. The inoculum was prepared by flooding the agar surface with 10 ml of sterilized double distilled water and scraping it with a spatula. The resulting spore suspension was filtered through three layers of cheesecloth. Conidial concentration was adjusted with a hemacytometer to 1 × 10⁶ conidia ml^-1. A conidia suspension was inoculated onto each of several stages of mushroom cultivation with a pipette. The control was spotted with double distilled water. In the case of infection during the inoculation and spawn running stages, the fungal mycelia colonized the media and hampered development of the mycelium of P. eryngii. In the regeneration and primordia formation stages of the host, the mycelium of the pathogen covered the surface of the plastic bottle containing the substrates and developed many spores. In the growing and harvesting stages, the surface of mushroom was overwhelmed by the mycelium of the fungal pathogen and turned pale or dark brown, accompanied by cracking of the stipe surface and finally rotting with a foul odor. These symptoms were similar to the observation from natural infection. The symptoms of the cobweb-like disease in A. bisporus (1,2) were observed within 5 to 7 days of inoculation with conidia suspensions of C. mycophilum. Fungi isolated from inoculated mushrooms were shown to be identical, based on phenotypic characteristic, to the inoculated strain used in these pathogenicity tests. No symptoms were observed on controls. To our knowledge, this is the first report on the occurrence of C. mycophilum on the edible mushroom P. eryngii in Korea. Based on the pathogenicity test results, the pathogen could attack P. eryngii in any cultivation stage, making it a potentially serious fungal pathogen in P. eryngii. References: (1) C. G. Back et al. J. Gen. Plant Pathol. 76:232, 2010. (2) R. H. Gaze. Mushroom J. 546:23, 1995. (3) F. J. Gea et al. Plant Dis. 95:1030, 2011. (4) H. M. Grogan and R. H. Gaze. Mycol. Res. 104:357, 2000.

Phylogenetic analysis of protozoa in the rumen contents of cow based on the 18S rDNA sequences

AIMS

To examine the diversity of protozoa in the rumen contents of cow.

METHODS AND RESULTS

Protozoa that inhabit the rumen were detected by PCR using protozoan-specific primers. Libraries of protozoan rDNA sequences were constructed from rumen fluid, solid tissues and epithelium. Twenty-three clones isolated from rumen fluid fell into two genera identified as Entodinium (69.6% of clones) and Epidinium (31.4% of clones). Of the clones isolated from rumen fluid, a moderate number were unidentifiable (30.4%).

CONCLUSIONS

The predominant protozoan genus identified in the whole rumen belonged to the Entodinium group (81.1%). Protozoa were not detected in the rumen epithelium.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings suggest that rumen fluid and solid tissues contain different protozoan populations that may play specific roles in rumen function. Quantitative PCR techniques and a more specific set of phylogenetic probes that distinguish between protozoan species are needed to determine the significance of newly identified groups and to determine the distribution of identified protozoan clusters in rumen microbial communities.

Biosorption of heavy metals using whole mold mycelia and parts thereof

Biosorption of heavy metals was carried out using whole mycelia and selected components of Aspergillus niger, Rhizopus oryzae and Mucor rouxii. Binding of copper, cadmium, nickel and zinc was considerably improved by treating the cell wall fraction with 4 M NaOH at 121 degrees C. Chitosan contributed most to the biosorptive capacity. 0.96 mmol copper was bound by 1 g of the treated mycelium of M. rouxii DSM 1191.

Enhancement of recombinant glucoamylase expression by introducing yeast GAL7 mRNA termination sequence

Glucoamylase gene (STA1) of Saccharomyces diastaticus was expressed in recombinant Saccharomyces cerevisiae systems. The yeast, GAL7 mRNA termination sequence, was introduced in the 3' noncoding region of the STA1 structural gene which was under the control of the SUC2 promoter and STA1 secretion signal sequence. This plasmid was named YEpSSG7 and was introduced into yeast S. cerevisiae MMY2 to construct recombinant S. cerevisiae MMY2SSG7. The GAL7 mRNA termination sequence enhanced the glucoamylase expression level by 3-5 times depending on the culture conditions compared to the result from the strain S. cerevisiae MMY2SUCSTA which did not contain the GAL7 mRNA termination sequence. Such an enhancement was not due to plasmid stability or plasmid copy number effects. Such an enhancement was primarily due to the fact that GAL7 mRNA termination sequence stabilized the STA1 mRNA 3' end.

Abdominal circumference vs abdominal area--which is better?

The efficacies of ultrasonic abdominal circumference (AC) and abdominal area (AA) measurements in the evaluation of intrauterine fetal growth were compared. The intraobserver random and technical errors were found to be significantly higher with AA measurements. The correlation with intrauterine fetal weight was observed to be better with AC as compared with AA measurements, the fetal weights being expressed as either linear regressions or multiple regressions involving the two parameters. Between 32 and 38 weeks, a single AC measurement detects 74 per cent of small-for-date fetuses, while a single AA measurement detects only 58 per cent of such fetuses. The false-positive rates were similar for the two parameters. It is concluded that AA measurements are no more useful than AC measurements in the routine assessment of intrauterine fetal growth.