SummaryThe velvet gene, veA, co-ordinates asexual and sexual development in the homothallic fungal species Aspergillus nidulans. Studies in Aspergillus parasiticus and Aspergillus fumigatus demonstrated that veA also regulates morphological differentiation in these species. Whether veA has the same role in morphogenesis in other fungal genera has not been investigated. In this work, we studied the role of the veA homologue, FvVE1, in the heterothallic fungus Fusarium verticillioides. Deletion of FvVE1 suppressed aerial hyphal growth and reduced colony surface hydrophobicity on solid media. In submerged cultures, FvVE1 deletion caused alterations in hyphal polarity, marked activation of conidiation and yeastlike growth. The latter was promoted by shaking to increase aeration of cultures. In addition, FvVE1 deletion markedly increased the ratio of macroconidia to microconidia. Supplementation of osmotic stabilizers restored the wild-type phenotype to deletion mutants, suggesting phenotypic alterations caused by FvVE1 deletion are related to cell wall defects. This is consistent with the hypersensitivity of FvVE1 deletion mutants to SDS and with the significant reduction in the mannoprotein content of mutants compared with the wild-type strain. However, no dramatic cell wall alterations were observed when mutants were examined by transmission electron microscopy. Our data strongly suggest that FvVE1 is important for cell wall integrity, cell surface hydrophobicity, hyphal polarity and conidiation pattern.

DNA is believed to be the molecular target for the cytotoxic activities of platinum (Pt) anticancer drugs. We report here a class of platinum(II)- and platinum(IV)-pyrophosphato complexes that exhibit cytotoxicity comparable with and, in some cases, better than cisplatin in ovarian cell lines (A2780, A2780/C30, and CHO), yet they do not show any evidence of covalent binding to DNA. Moreover, some of these compounds are quite effective in cisplatin- and carboplatin-resistant cell line A2780/C30. The lack of DNA binding was demonstrated by the absence of a detectable Pt signal by atomic absorption spectroscopy using isolated DNA from human ovarian cells treated with a platinum(II)-pyrophosphato complex, ( trans -1,2-cyclohexanediamine)(dihydrogen pyrophosphato) platinum(II), (pyrodach-2) and from NMR experiments using a variety of nucleotides including single- and double-stranded DNA. Furthermore, pyrodach-2 exhibited reduced cellular accumulations compared with cisplatin in cisplatin- and carboplatin-resistant human ovarian cells, yet the IC 50 value for the pyrophosphato complex was much less than that of cisplatin. Moreover, unlike cisplatin, pyrodach-2 treated cells overexpressed fas and fas-related transcription factors and some proapoptotic genes such as Bak and Bax. Data presented in this report collectively indicate that pyrodach-2 follows different cytotoxic mechanisms than does cisplatin. Unlike cisplatin, pyrodach-2 does not undergo aquation during 1 week and is quite soluble and stable in aqueous solutions. Results presented in this article represent a clear paradigm shift not only in expanding the molecular targets for Pt anticancer drugs but also in strategic development for more effective anticancer drugs.

Secondary metabolism and development are linked in Aspergillus through the conserved regulatory velvet complex composed of VeA, VelB, and LaeA. The founding member of the velvet complex, VeA, shuttles between the cytoplasm and nucleus in response to alterations in light. Here we describe a new interaction partner of VeA identified through a reverse genetics screen looking for LaeA-like methyltransferases in Aspergillus nidulans. One of the putative LaeA-like methyltransferases identified, LlmF, is a negative regulator of sterigmatocystin production and sexual development. LlmF interacts directly with VeA and the repressive function of LlmF is mediated by influencing the localization of VeA, as over-expression of llmF decreases the nuclear to cytoplasmic ratio of VeA while deletion of llmF results in an increased nuclear accumulation of VeA. We show that the methyltransferase domain of LlmF is required for function; however, LlmF does not directly methylate VeA in vitro. This study identifies a new interaction partner for VeA and highlights the importance of cellular compartmentalization of VeA for regulation of development and secondary metabolism.

Flavohemoglobins are widely distributed in both prokaryotes and eukaryotes. These proteins are involved in reducing nitric oxide levels. Deletion of the Aspergillus nidulans flavohemoglobin gene fhbA induced sexual development and decreased sterigmatocystin production. Supplementation with a nitric oxide-releasing compound promoted cleistothecial formation and increased nsdD and steA expression, indicating that nitric oxide induces sexual development. This is the first study on the effect of nitric oxide on morphogenesis and secondary metabolism in fungi.Nitric oxide (NO) is a signaling compound of great importance in biological systems (7,10,21). This molecule can also cause nitrosative stress which is potentially remediated by the widely distributed flavohemoglobins (FHbs) found in both eukaryotes and prokaryotes (4, 7). Extensive research on FHb proteins from bacteria and yeast revealed their structure, function, and mechanism of action (3,7,17). Earlier studies have shown that FHbs in organisms such as Saccharomyces cerevisiae, Alcaligenes eutrophus, and Escherichia coli share similar steady-state NO dioxygenation kinetics (7). Through a dioxygenase-mediated reaction, FHbs, in the presence of molecular O 2 , converts NO into nontoxic nitrate ions. FHb proteins contain a hemoglobin-like domain with a noncovalently bound heme B protein and a reductase domain with binding sites for FAD and NAD(P)H. It is known that fhb genes are activated by various agents, such as nitrate, nitrite, NO, and NO-releasing agents (5,7,8,11,20,24). In aspergilli, the conversion of NO to NO 3 Ϫ by FHbs, Fhb1 and Fhb2 in Aspergillus oryzae (30) and FhbA and FhbB in the filamentous fungus model Aspergillus nidulans, has been demonstrated (24). The present work involves the study of the role of FHbs and NO in fungal development and secondary metabolism.Fungal strains and growth conditions. Aspergillus nidulans Cib08 (biA1 yA2), CibA (biA1 yA2 ⌬fhbA::argB), CibB (biA1 yA2 ⌬fhbB::argB) (described in reference 24), and FGSCA4 were used in this study. The strains were cultured on glucose minimum medium (GMM) plus the appropriate supplements for the corresponding auxotrophic markers (13). Medium was supplemented with 1.5 mM diethylenetriamine-NoNoate (Sigma), a NO-releasing compound, after sterilization when indicated. Solid medium was prepared by adding 10 g/liter agar. Strains were stored as 30% glycerol stocks at Ϫ80°C. Morphological studies.Plates containing 25 ml of solid GMM plus the appropriate supplements were top agar inoculated with 5 ϫ 10 6 spores per plate of medium. The cultures were wrapped and incubated at 37°C in the dark. Cores (8-mm diameter) were collected from each spread plate and examined for cleistothecium production. Ethanol (70%) was sprayed on the core surface to facilitate the visualization of cleistothecia under the microscope. The experiments included five replicates and were repeated twice, with similar results. mRNA analysis. Total RNA was isolated from mycelia at 48 h and 72 h after inoculation as previously ...

A native homoethanol pathway (pyruvate-to-acetyl-CoA-to-acetaldehyde-to-ethanol) was engineered in Escherichia coli B. The competing fermentation pathways were eliminated by chromosomal deletions of the genes encoding for fumarate reductase (frdABCD), lactate dehydrogenase (ldhA), acetate kinase (ackA), and pyruvate formate lyase (pflB). For redox balance and anaerobic cell growth, the pyruvate dehydrogenase complex (aceEF-lpd, a typical aerobically-expressed operon) was highly expressed anaerobically using a native anaerobic inducible promoter. The resulting strain SZ420 (DeltafrdBC DeltaldhA DeltaackA DeltafocA-pflB DeltapdhR::pflBp6-pflBrbs-aceEF-lpd) contains no foreign genes and/or promoters and efficiently ferments glucose and xylose into ethanol with a yield of 90% under anaerobic conditions.