Proteome analysis of Arabidopsis seedlings exposed to bacterial volatiles.

Plant root-associated bacteria (rhizobacteria) elicit plant basal immunity referred to as induced systemic resistance (ISR) against multiple pathogens. Among multi-bacterial determinants involving such ISR, the induction of ISR and promotion of growth by bacterial volatile compounds was previously reported. To exploit global de novo expression of plant proteins by bacterial volatiles, proteomic analysis was performed after exposure of Arabidopsis plants to the rhizobacterium Bacillus subtilis GB03. Ethylene biosynthesis enzymes were significantly up-regulated. Analysis by quantitative reverse transcriptase polymerase chain reaction confirmed that ethylene biosynthesis-related genes SAM-2, ACS4, ACS12, and ACO2 as well as ethylene response genes, ERF1, GST2, and CHIB were up-regulated by the exposure to bacterial volatiles. More interestingly, the emission of bacterial volatiles significantly up-regulated both key defense mechanisms mediated by jasmonic acid and salicylic acid signaling pathways. In addition, high accumulation of antioxidant proteins also provided evidence of decreased sensitivity to reactive oxygen species during the elicitation of ISR by bacterial volatiles. The present results suggest that the proteomic analysis of plant defense responses in bacterial volatile-mediated ISR can reveal the mechanisms of plant basal defenses orchestrated by endogenous ethylene production pathways and the generation of reactive oxygen species.

Identification of Lacrymaria velutina (Pers. Ex Fr.) Konrad & Maubl. from Micheon-myeon, Jinju-city, Korea.

We identified Lacrymaria velutina of the Coprinaceae in Korea. The unusually large and sturdy fruiting body, fibrillose to fibrillose-scaly cap and stalk without a volva with an obscure superior hairy ring zone or hairy annulus, and blackish brown, warted spores distinguished this species from closely related Psathyrella species. An illustrated account of the microscopic traits is presented. Fruiting bodies with obtusely hemispherical caps, 2.5~6 cm, becoming convex with age; surface dry, densely fibrillose-scaly with split margin; stipe, 4.5~6 cm, equal, hollow, fibrillose, dry, whitish above the superior ring zone, light brown below; crowded gills, adnexed, dark black at maturity. Pileipellis typically cellular with the gill edge appearing white and beaded. Blackish brown basidiospores that discolor in concentrated sulfuric acid. Spores elliptical, warted, 9~11 × 6~8 µm, with prominent snout-like germpores. Cheilocystidia abundant, 57~68 × 19~25 µm, and narrowly elongated clavate, often clustered in threes or fours. Pleurocystidia rarely present, 45~47.5 × 12~13 µm, and clavate to utriform. This trait distinguishes our sample as L. velutina from other Psathyrella spp. of the Coprinaceae, which have smooth spores. This taxon was clarified by the observation that Psathyrella spores fade in concentrated sulfuric acid. A molecular phylogenetic study revealed that our specimen was Lacrymria velutipes, which is closely related to Lacrymaria lacrymabunda. Moreover, those two species are clearly distinguishable from other Psathyrella species, which agreed with the morphologically distinctive traits described above. We believe that this is the first report of this taxon, which has not been described in Korea.

Identification of potential DREB2C targets in Arabidopsis thaliana plants overexpressing DREB2C using proteomic analysis.

The dehydration responsive element binding protein 2C (DREB2C) is a dehydration responsive element/C-repeat (DRE/CRT)-motif binding transcription factor that induced by mild heat stress. Previous experiments established that overexpression of DREB2C cDNA driven by the cauliflower mosaic virus 35S promoter (35S:DREB2C) resulted in increased heat tolerance in Arabidopsis. We first analyzed the proteomic profiles in wild-type and 35S:DREB2C plants at a normal temperature (22 degrees C), but could not detect any differences between the proteomes of wild-type and 35S:DREB2C plants. The transcript level of DREB2C in 35S:DREB2C plants after treatment with mild heat stress was increased more than two times compared with expression in 35S:DREB2C plants under unstressed condition. A proteomic approach was used to decipher the molecular mechanisms underlying thermotolerance in 35S:DREB2C Arabidopsis plants. Eleven protein spots were identified as being differentially regulated in 35S:DREB2C plants. Moreover, in silico motif analysis showed that peptidyl-prolyl isomerase ROC4, glutathione transferase 8, pyridoxal biosynthesis protein PDX1, and elongation factor Tu contained one or more DRE/CRT motifs. To our knowledge, this study is the first to identify possible targets of DREB2C transcription factors at the protein level. The proteomic results were in agreement with transcriptional data.

Biodegradation and saccharification of wood chips of Pinus strobus and Liriodendron tulipifera by white rot fungi.

Degradation and glucose production from wood chips of white pine (Pinus strobus) and tulip tree (Liriodendron tulipifera) by several white rot fungi were investigated. The highest weight losses from 4 g of wood chips of P. strobus and L. tulipifera by the fungal degradation on yeast extractmalt extract-glucose agar medium were 38% of Irpex lacteus and 93.7% of Trametes versicolor MrP 1 after 90 days, respectively. When 4 g of wood chips of P. strobus and L. tulipifera biodegraded for 30 days were treated with cellulase, glucose was recovered ot the highest values of 106 mg/g degraded wood by I. lacteus and 450 mg/g degraded wood by T. versicolor. The weight loss of 10 g of wood chip of L. tulipifera by T. versicolor on the nutrient non-added agar under the nonsterile conditions was 35% during 7 weeks of incubation, and the cumulative amount of glucose produced during this period was 239 mg without cellulase treatment. The activities of ligninolytic enzymes (lignin peroxidase, manganese peroxidase, and laccase) of fungi tested did not show a high correlation with degradation of the wood chips and subsequent glucose formation. These results suggest that the selection of proper wood species and fungal strain and optimization of glucose recovery are all necessary for the fungal pretreatment of woody biomass as a carbon substrate.

Identification of Diachea leucopodia on Strawberry from Greenhouse in Korea.

We have detected the slime mold, Diachea leucopodia (GNU06-10) in a strawberry greenhouse located in Sancheong-gun, Gyeongnam. Typical fruiting bodies had developed gregariously on the strawberry leaves, petioles, and plant debris on ground soil habitat, and also surprisingly on plastic pipes and a vinyl covering. Field samples were examined via stereomicroscopy, light microscopy, and SEM for the determination of morphological characteristics. Dark-brown to black spores formed gregariously within the stipitate cylindrical sporangium, and were covered by an iridescent peridium, which may be intact at maturity, or may have disintegrated. The upper portion of the peridium generally breaks up to expose the spores, whereas the lower portion was usually persistent. The results of energy dispersive X-ray spectrometer (EDS) analysis showed that lime was present in the stalk and columella but absent from the spores, capillitium, and peridium. The above characteristics confirm its taxonomic position in the genus Diachea. However, this genus is intermediate in character between the Physarales and Stemonitales of the Myxogastromycetidae. Hence, this genus had been classified as a member of the Stemonitales until the mid-1970's, on the basis of its iridescent peridium and noncalcareous capillitial system, similar to Comatricha of the Stemonitaceae. By way of contrast, emphasis on morphological characteristics, most notably the calcareous stalk and typical columella, places Diachea within the order Physarales. The presence of a phaneroplasmodium during the trophic stage and lime deposition in its sporophores, as was confirmed in this work, supported the inclusion of Diachea in the Physarales, and the noncalcareous capillitial system verified its identification as a member of the Didymiaceae. Further characteristics of the species D. leucopodia include the following: phaneroplasmodium, spore globose 7.5 µm in diameter, very minutely roughened; sporangia 500 µm × 1mm, more or less cylindrical, gregarious, stalked 1.2mm; stalk and columella white.