Novel mechanism of hydrogen peroxide for promoting efficient natamycin synthesis in Streptomyces.

The mechanism of regulation of natamycin biosynthesis by Streptomyces in response to oxidative stress is unclear. Here, we first show cholesterol oxidase SgnE, which catalyzes the formation of H2O2 from sterols, triggered a series of redox-dependent interactions to stimulate natamycin production in S. gilvosporeus. In response to reactive oxygen species, residues Cys212 and Cys221 of the H2O2-sensing consensus sequence of OxyR were oxidized, resulting in conformational changes in the protein: OxyR extended its DNA-binding domain to interact with four motifs of promoter p sgnM . This acted as a redox-dependent switch to turn on/off gene transcription of sgnM, which encodes a cluster-situated regulator, by controlling the affinity between OxyR and p sgnM , thus regulating the expression of 12 genes in the natamycin biosynthesis gene cluster. OxyR cooperates with SgnR, another cluster-situated regulator and an upstream regulatory factor of SgnM, synergistically modulated natamycin biosynthesis by masking/unmasking the -35 region of p sgnM depending on the redox state of OxyR in response to the intracellular H2O2 concentration. IMPORTANCE Cholesterol oxidase SgnE is an indispensable factor, with an unclear mechanism, for natamycin biosynthesis in Streptomyces. Oxidative stress has been attributed to the natamycin biosynthesis. Here, we show that SgnE catalyzes the formation of H2O2 from sterols and triggers a series of redox-dependent interactions to stimulate natamycin production in S. gilvosporeus. OxyR, which cooperates with SgnR, acted as a redox-dependent switch to turn on/off gene transcription of sgnM, which encodes a cluster-situated regulator, by masking/unmasking its -35 region, to control the natamycin biosynthesis gene cluster. This work provides a novel perspective on the crosstalk between intracellular ROS homeostasis and natamycin biosynthesis. Application of these findings will improve antibiotic yields via control of the intracellular redox pressure in Streptomyces.

Methane plasma-mediated phase engineering of Ni nanosheets for alkaline hydrogen evolution.

Engineering of the crystal structures of metallic nanomaterials is an alternative avenue to control the size and shape of nanocatalysts. However, the phase-controlled synthesis of Ni nanocatalysts is challenging because of its low reduction potential under mild conditions. We developed a room-temperature CH4 plasma conversion of Ni(OH)2 nanosheets to hexagonal close packed (hcp) Ni while maintaining a pristine shape. Increasing the temperature resulted in the formation of face-centered cubic (fcc) Ni. The hcp Ni nanosheets exhibited an overpotential of 85 mV at 10 mA cm-2 for an electrocatalytic hydrogen evolution reaction (HER) in alkaline solution, which was superior to that of the fcc (122 mV) counterpart. Density-functional-theory calculations demonstrated that during the HER, the d-band center of hcp Ni was closer to the Fermi level, which aided the formation of H2 molecules. This work could facilitate the synthesis of other metastable metals and metallic alloys with high efficiency for various applications.

MacRS controls morphological differentiation and natamycin biosynthesis in Streptomyces gilvosporeus F607.

Streptomyces gilvosporeus F607 produces large amounts of natamycin in a process regulated by multiple networks, including two-component systems (TCSs). The macR and macS genes, which are annotated as rs12540 and rs12545, respectively, in S. gilvosporeus F607, affect natamycin biosynthesis and sporulation. The findings of this study indicate that deletion of macRS from S. gilvosporeus F607 prevents the production of natamycin, delays spore formation (according to scanning electron microscopy), and results in aerial hyphae lacking compartments separated by septa (according to transmission electron microscopy). Real-time quantitative polymerase chain reaction (RT-qPCR) analyses revealed that the expression levels of natamycin biosynthesis-related genes and genes essential for septum formation during sporulation were affected in the ΔmacRS mutant strain. Molecular simulations and electrophoretic mobility shift assays (EMSAs) suggested MacR not only interacted with the intergenic region of sgnM and sgnR, but also with the promoter of penicillin-binding protein gene ftsL required for cell division. sgnR promoter was presumed to be the binding target of MacR based on the RT-qPCR results. MacR had different affinity with two binding sites: one was located at ftsL promoter region with a perfect inverted repeats 'TGAGTACGCGTACTCA', the other was located at the presumed sgnR promoter with an imperfect inverted repeats 'TGAAGGTGCTGGACTCA'. We propose a hypothesis of a three-level regulatory pathway based on pleiotropic transcriptional regulator MacR and its target genes sgnR and ftsL; the pathway activates natamycin biosynthesis and influences septum development via direct and indirect effects in S. gilvosporeus F607.

Phenotypic and proteomic characteristics of sorghum (Sorghum bicolor) albino lethal mutant sbe6-a1.

Leaf color mutants are ideal materials for chloroplast development and photosynthetic mechanism research. Here, we characterized an EMS (ethyl methane sulfonate)-mutagenized sorghum (Sorghum bicolor) mutant, sbe6-a1, in which the severe disruption in chloroplast structure and a chlorophyll deficiency promote an albino leaf phenotype and lead to premature death. The proteomic analyses of mutant and its progenitor wild-type (WT) were performed using a Q Exactive plus Orbitrap mass spectrometer and 4,233 proteins were accurately quantitated. The function analysis showed that most of up-regulated proteins in mutant sbe6-a1 had not been well characterized. GO-enrichment analysis of the differentially abundant proteins (DAPs) showed that up-regulated DAPs were significantly enriched in catabolic process and located in mitochondria, while down regulated DAPs were located in chloroplasts and participated in photosynthesis and some other processes. KEGG pathway-enrichment analyses indicated that the degradation and metabolic pathways of fatty acids, as well as some amino acids and secondary metabolites, were significantly enhanced in the mutant sbe6-a1, while photosynthesis-related pathways, some secondary metabolites' biosynthesis and ribosomal pathways were significantly inhibited. Analysis also shows that some DAPs, such as FBAs, MDHs, PEPC, ATP synthase, CABs, CHLM, PRPs, pathogenesis-related protein, sHSP, ACP2 and AOX may be closely associated with the albino phenotype. Our analysis will promote the understanding of the molecular phenomena that result in plant albino phenotypes.

Clear cell papillary renal cell carcinoma: a clinicopathologic analysis of 6 cases.

Clear cell papillary renal cell carcinoma (CCPRCC) is a newly described variant of renal cell carcinoma (RCC) which is composed mainly of cells with clear cytoplasm arranged in cystic and papillary patterns. We report the clinicopathologic features, prognosis and differential diagnosis of 6 Clear Cell Papillary Renal Cell Carcinomas. The clinical information and follow-up data were analyzed. The patients were six males with median age of 52.5 years. Case 1 revealed dense calcification and ossification. Cases 2 and 3 contain a variably prominent smooth muscle stromal component. CA-IX, CK7, PAX-8 and VIM were positive in all cases. TFE3 and AMACR were not expressed in any tumor. CD10 was negative in 5 of 6 cases .The patients were followed for 13~55 months with no local tumor recurrences and tumor metastasis. The CCPRCC was associated with a more favorable outcome. These were low-grade and low-stage renal tumors. No lymph node or distant metastasis of the six tumors.

Hyalinizing trabecular tumor of the thyroid: Case report and review of the literature.

In 1987, Carney et al described a rare thyroid tumor termed hyalinizing trabecular adenoma presenting characteristics consisting of a trabecular growth pattern and hyalinizing stroma. In subsequent reports, the observed nuclear features and RET alterations led this tumor to be linked to papillary carcinoma. Subsequent reports concerning hyalinizing trabecular carcinoma further complicated its classification. To avoid uncertainties, the definition of hyalinizing trabecular tumor (HTT) is more widely used. Herein, a case of HTT is reported in detail, and the circumstances are also discussed. HTT is thought to be particularly differentiated from papillary carcinoma despite the identical high frequency of nuclear grooves and cytoplasmic inclusions, and MIB-1-positive staining is one of the most accurate diagnostic methods due to the distinct membrane-positive pattern noted in HTT. It is believed that most HTTs are benign and lobectomy is the standard treatment. Pathologists should offer surgeons information concerning diagnosis overlapping with effective treatment.

[A clinicopathologic study of 9 cases of primary pulmonary extranodal marginal zone B-cell lymphoma].

BACKGROUND: To study the clinicopathologic and immunohistochemical features of primary pulmonary extranodal marginal zone B-cell lymphomas (MALT lymphomas). METHODS: Immunohistochemical staining for LCA, CD20, CD45RO, CD5, cyclinD1, Ki-67, immunoglobine light chain κ and λ, CK and NSE was carried out in 9 patients with primary pulmonary extranodal marginal zone B-cell lymphomas by the S-P methods. RESULTS: According to the histological pattern and immunohistochemical features, all patients were diagnosed as primary pulmonary extranodal marginal zone B-cell lymphomas. There were four males and five females with a median age of 51.5 years (range from 37 to 64 years). The tumor cells were positive for LCA and CD20, however, the positive rates of Ki-67 were low. The tumor cells expressed immunoglobine light chain restriction λ in 5 cases , κ in 1 case, both λ and κ in 1 case, and neither of them in 2 cases. The tumor cells were negative for CD45RO, CD5, cyclineD1, CK, NSE in all patients. CONCLUSIONS: Primary pulmonary extranodal marginal zone B-cell lymphomas are inert lymphomas which are easily misdiagnosed. The evaluation of pathologic features and immunohistochemistry are useful and practical in the diagnosis and differential diagnosis of primary pulmonary extranodal marginal zone B-cell lymphomas.