Insecticidal Activities of Chloramphenicol Derivatives Isolated from a Marine Alga-Derived Endophytic Fungus, Acremonium vitellinum, against the Cotton Bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae).

A great deal of attention has been focused on the secondary metabolites produced by marine endophytic fungi, which can be better alternatives to chemicals, such as biopesticides, for control of polyphagous pests. On the basis of its novel biocontrol attributes, chemical investigation of a marine alga-derived endophytic fungus, Acremonium vitellinum, resulted in the isolation of three chloramphenicol derivatives (compounds 1⁻3). Their chemical structures were elucidated by detailed analysis of their nuclear magnetic resonance spectra, high-resolution electrospray ionization mass spectrometry, and by comparison with the data available in the literature. In this paper, compound 2 was firstly reported as the natural origin of these fungal secondary metabolites. The insecticidal activities of compounds 1⁻3 against the cotton bollworm, Helicoverpa armigera, were evaluated. The natural compound 2 presented considerable activity against H. armigera, with an LC50 value of 0.56 ± 0.03 mg/mL (compared to matrine with an LC50 value of 0.24 ± 0.01 mg/mL). Transcriptome sequencing was used to evaluate the molecular mechanism of the insecticidal activities. The results presented in this study should be useful for developing compound 2 as a novel, ecofriendly and safe biopesticide.

A homologue of the Aspergillus velvet gene regulates both cephalosporin C biosynthesis and hyphal fragmentation in Acremonium chrysogenum.

The Aspergillus nidulans velvet (veA) gene encodes a global regulator of gene expression controlling sexual development as well as secondary metabolism. We have identified the veA homologue AcveA from Acremonium chrysogenum, the major producer of the beta-lactam antibiotic cephalosporin C. Two different disruption strains as well as the corresponding complements were generated as a prelude to detailed functional analysis. Northern hybridization and quantitative real-time PCR clearly indicate that the nucleus-localized AcVEA polypeptide controls the transcriptional expression of six cephalosporin C biosynthesis genes. The most drastic reduction in expression is seen for cefEF, encoding the deacetoxycephalosporine/deacetylcephalosporine synthetase. After 120 h of growth, the cefEF transcript level is below 15% in both disruption strains compared to the wild type. These transcriptional expression data are consistent with results from a comparative and time-dependent high-performance liquid chromatography analysis of cephalosporin C production. Compared to the recipient, both disruption strains have a cephalosporin C titer that is reduced by 80%. In addition to its role in cephalosporin C biosynthesis, AcveA is involved in the developmentally dependent hyphal fragmentation. In both disruption strains, hyphal fragmentation is already observed after 48 h of growth, whereas in the recipient strain, arthrospores are not even detected before 96 h of growth. Finally, the two mutant strains show hyperbranching of hyphal tips on osmotically nonstabilized media. Our findings will be significant for biotechnical processes that require a defined stage of cellular differentiation for optimal production of secondary metabolites.

Effects of feeding diets containing endophyte-infected fescue seed on luteinizing hormone secretion in postpartum beef cows and in cyclic heifers and cows.

Two experiments were conducted to investigate the effect of feeding endophyte (Acremonium coenophialum)-infected fescue (Festuca arundinacea Shreb.) seed on LH secretion in postpartum beef cows and in cycling heifers and cows. In Exp. 1, spring-calving primiparous Angus cows (n = 16) were pair-fed for 75 d diets that contained endophyte-free or endophyte-infected (95%) fescue seed that contained 1.3 micrograms/g of ergovaline and 5.2 mg/g of saturated pyrrolizidines. Serial blood samples for basal and GnRH-stimulated serum LH analysis were obtained on d 7, 28, 42, and 56 of the study. The endophyte had no effect on LH secretion (basal, pulse frequency, and amplitude) or milk production. Average daily gain was decreased (P < .05) in cows that consumed infected fescue seed compared with controls (-.20 vs -.01 kg, respectively). Basal serum prolactin concentrations were reduced (P < .01) in treated compared with control cows (8.9 vs 25.4 ng/mL, respectively) on d 70. In Exp. 2, cycling Angus heifers (n = 8; age = 2 yr) and cows (n = 8; age = 4 yr) stratified by age were pair-fed for 40 d diets that contained the noninfected or the highly infected fescue seed. Estrus was synchronized by prostaglandin F2 alpha (d 18 and 28). Serial blood samples for serum LH analysis were obtained on d 28 (luteal phase) and d 30 (follicular phase). The endophyte did not affect LH (P > .28) or prolactin (P > .16) secretion, whereas ADG was decreased (P < .05) in treated compared with control animals (.32 vs .70 kg/d, respectively).