Junsang Oh

Regulation of a phenylalanine ammonia lyase (BbPAL) by calmodulin in response to environmental changes in the entomopathogenic fungus Beauveria bassiana

Phenylalanine ammonia lyase (PAL, E.C. 4.3.1.5) catalyses the deamination of L -phenylalanine to trans-cinnamic acid and ammonia, facilitating a critical step in the phenylpropanoid pathway that produces a variety of secondary metabolites. In this study, we isolated BbPAL gene in the entomopathogenic fungus Beauveria bassiana. According to multiple sequence alignment, homology modelling and in vitro PAL activity, we demonstrated that BbPAL acts as a typical PAL enzyme in B. bassiana. BbPAL interacted with calmodulin (CaM) in vitro and in vivo, indicating that BbPAL is a novel CaM-binding protein. The functional role of CaM in BbPAL action was to negatively regulate the BbPAL activity in B. bassiana. High-performance liquid chromatography analysis revealed that L -phenylalanine was reduced and trans-cinnamic acid was increased in response to the CaM inhibitor W-7. Dark conditions suppressed BbPAL activity in B. bassiana, compared with light. In addition, heat and cold stresses inhibited BbPAL activity in B. bassiana. Interestingly, these negative effects of BbPAL activity by dark, heat and cold conditions were recovered by W-7 treatment, suggesting that the inhibitory mechanism is mediated through stimulation of CaM activity. Therefore, this work suggests that BbPAL plays a role in the phenylpropanoid pathway mediated by environmental stimuli via the CaM signalling pathway.

Regulation of MAP kinase Hog1 by calmodulin during hyperosmotic stress

Mitogen-activated protein kinase (Hog1 in yeast and ortholog p38 in human cells) plays a critical role in the signal transduction pathway that is rapidly activated under multiple stress conditions. Environmental stress stimuli such as hyperosmotic stress cause changes in cellular ATP metabolism required for hyperosmotic stress tolerance. Furthermore, hyperosmotic stress induces rapid Ca2+ signals in eukaryotic cells. These Ca2+ signals can be decoded by Ca2+ sensor calmodulin (CaM). By using genetic and biochemical approaches, we demonstrate that Hog1 is a novel CaM-binding protein, and that CaM-binding to Hog1 is involved in the mediation of the hyperosmotic stress signaling pathway. In addition, we show that p38α, a human ortholog of Hog1, interacts with CaM, suggesting that the CaM-binding feature of Hog1/p38α is evolutionarily conserved in eukaryotic cells. Hog1 is likely involved in cellular ATP regulation through CaM signaling during hyperosmotic stress. Therefore, this work suggests that Hog1 plays an important role in connecting CaM signaling with the hyperosmotic stress pathway by directly interacting with CaM in Saccharomyces cerevisiae.

Calmodulin-mediated suppression of 2-ketoisovalerate reductase in Beauveria bassiana beauvericin biosynthetic pathway.

Ketoisovalerate reductase (KIVR, E.C. 1.2.7.7) mediates the specific reduction of 2-ketoisovalerate (2-Kiv) to d-hydroxyisovalerate (d-Hiv), a precursor for beauvericin biosynthesis. Beauvericin, a famous mycotoxin produced by many fungi, is a cyclooligomer depsipeptide, which has insecticidal, antimicrobial, antiviral, and cytotoxic activities. In this report, we demonstrated that Beauveria bassiana 2-ketoisovalerate reductase (BbKIVR) acts as a typical KIVR enzyme in the entomopathogenic fungus B. bassiana. In addition, we found that BbKIVR interacts with calmodulin (CaM) in vitro and in vivo. The functional role of CaM-binding to BbKIVR was to negatively regulate the BbKIVR activity in B. bassiana. Environmental stimuli such as light and salt stress suppressed BbKIVR activity in B. bassiana. Interestingly, this negative effect of BbKIVR activity by light and salt stress was recovered by CaM inhibitors, suggesting that the inhibitory mechanism is mediated through stimulation of CaM activity. Therefore, this work suggests that BbKIVR plays an important role in the beauvericin biosynthetic pathway mediated by environmental stimuli such as light and salt stress via the CaM signaling pathway.

A Brief Chronicle of the Genus Cordyceps Fr., the Oldest Valid Genus in Cordycipitaceae (Hypocreales, Ascomycota)

Abstract The earliest pre-Linnaean fungal genera are briefly discussed here with special emphasis on the nomenclatural connection with the genus Cordyceps Fr. Since its valid publication under the basidiomycetous genus Clavaria Vaill. ex L. (Clavaria militaris L. Sp. Pl. 2:1182, 1753), the genus Cordyceps has undergone nomenclatural changes in the post-Linnaean era, but has stood firmly for approximately 200 years. Synonyms of Cordyceps were collected from different literature sources and analyzed based on the species they represent. True synonyms of Cordyceps Fr. were defined as genera that represented species of Cordyceps Fr. emend. G. H. Sung, J. M. Sung, Hywel-Jones & Spatafora. The most common synonyms of Cordyceps observed were Clavaria and Sphaeria Hall, reported in the 18th and in the first half of the 19th century, respectively. Cordyceps, the oldest genus in the Cordyceps s. s. clade of Cordycipitaceae, is the most preferred name under the “One Fungus = One Name” principle on priority bases.

Identification of calmodulin binding proteins in the entomopathogenic fungus Beauveria bassiana

Calmodulin (CaM) is a primary Ca2+ receptor and plays a pivotal role in a variety of cellular responses in eukaryotes. Even though a large number of CaM-binding proteins are well known in yeast, plants, and animals, little is known regarding CaM-targeted proteins in filamentous fungi. To identify CaM-binding proteins in filamentous fungi, we used a proteomics method coupled with co-immunoprecipitation (CoIP) and MALDI-TOF/TOF mass spectrometry (MS) in Beauveria bassiana. Through this method, we identified ten CaM-binding proteins in B. bassiana. One of the CaM-targeted proteins was the heat shock protein 70 (BbHSP70) in B. bassiana. Our biochemical study showed that ATP inhibits the molecular interaction between BbHSP70 and CaM, suggesting a regulatory mechanism between CaM and ATP for regulating BbHSP70.

Species identity of Phellinus linteus (sanghuang) extensively used as a medicinal mushroom in Korea

Sanghuang is a medicinal mushroom that has gained particular attention in Korea. It has been extensively studied for the past few decades as a natural immune booster and cancer suppressor. Although the scientific name, Phellinus linteus, has been commonly used to refer to the sanghuang mushroom, the species identity of sanghuang has been called into question due to the ambiguity of its circumscription and the inadequacy of morphological distinctions within allied species. Because the species concept of sanghuang has been elucidated by recent molecular phylogenetic studies, it has become necessary to clarify the taxonomic positions of sanghuang strains extensively utilized in Korea. We conducted a phylogenetic analysis of 74 strains belonging to the P. linteus-baumii complex based on ITS nrDNA sequences. Parental stains of sanghuang varieties formally registered in the Korea Seed & Variety Service, including ASI 26046 (Corea sanghuang), 26114 (Boolro), and 26115 (HK 1-ho) were grouped with Sanghuangporus sanghuang instead of P. linteus in the inferred phylogeny.

Neuroprotective and therapeutic effect of Cordyceps militaris on ischemia-induced neuronal death and cognitive impairments

Cordyceps militaris is a type of fungus consumed by people all over the world and renowned for their nutritional benefits and herbal formulas to promote health and longevity. In the present study investigation was carried out to explore the therapeutic properties and neuroprotective effect of the C. militaris on ischemic brain neuronal injury, impairment of memory and learning in experimental rats induced by a global cerebral ischemia-reperfusion injury in WISTAR rats. Vascular Dementia with transient global brain injuries induced by a four-vessel occlusion (4-VO) in WISTAR rats. Further, donepezil (5 mg/kg) and C. militaris was (100 and 300 mg/kg, p.o.) were orally administered for 7 days in 4-VO WISTAR rats. C. militaris has the ability to improve memory impairments due to global cerebral ischemia and scopolamine-induced memory deterioration. Our present findings suggest that C. militaris may be a potential candidate for the neuroprotection of hippocampus and the recovery of various vascular dementia or neuroinflammatory disorders.

The complete mitochondrial genome of Sanghuangporus sanghuang (Hymenochaetaceae, Basidiomycota)

Abstract Sanghuang is a polypore mushroom, which has been widely used in oriental medicine. Since recent molecular phylogenetic studies elucidated its species delimitation, Sanghaungporus sanghuang became the official name of this fungus. In this study, the complete sequence of the mitochondrial DNA of S. sanghuang was determined. The whole genome was 112,060 bp containing 14 proteins, 2 ribosomal RNA subunits, and 45 transfer RNAs. The overall GC content of the genome was 23.21%. A neighbour-joining tree based on atp6 sequence data showed its close relationship with the species of Ganoderma and Trametes.

New Records of Xylaria Species in Korea: X. ripicola sp. nov. and X. tentaculata.

Abstract During a Korean mushroom diversity survey from 2011 to 2014, we found one new Xylaria species (X. ripicola sp. nov.) and one Xylaria species that had not been previously observed in Korea (X. tentaculata). To confirm the phylogenetic placement of the new species, we conducted a phylogenetic investigation based on internal transcribed spacer regions of ribosomal DNA sequences. Additionally, the new species, X. ripicola, was subsequently analyzed for RNA polymerase II subunit sequences. We also evaluated the macroscopic and microscopic features of this species. Herein, X. ripicola is described as a new species that was collected from a natural beach habitat and X. tentaculata is formally reported as newly found in Korea.