Minyu Luo

A novel phytotoxic nonenolide from Phomopsis sp. HCCB03520.

A novel phytotoxic nonenolide, (6S,7R,9R)‐6,7‐dihydroxy‐9‐propylnon‐4‐eno‐9‐lactone (1), was isolated from solid cultures of the endophytic fungus Phomopsis sp. HCCB03520, together with three known compounds, cytochalasin H (2), cytochalasin N (3), and epoxycytochalasin H (4). The structures of these compounds were elucidated through spectroscopic analysis, and the absolute configurations were determined by CD spectroscopy. Phytotoxic activities of compounds 1–4 were also investigated. Compound 1 showed phytotoxic activity on germination and radicle growth of Medicago sativa, Trifolium hybridum, and Buchloe dactyloides.

A regulatory gene (ECO‐orf4) required for ECO‐0501 biosynthesis in Amycolatopsis orientalis

ECO‐0501 is a novel linear polyene antibiotic, which was discovered from Amycolatopsis orientalis. Recent study of ECO‐0501 biosynthesis pathway revealed the presence of regulatory gene: ECO‐orf4. The A. orientalis ECO‐orf4 gene from the ECO‐0501 biosynthesis cluster was analyzed, and its deduced protein (ECO‐orf4) was found to have amino acid sequence homology with large ATP‐binding regulators of the LuxR (LAL) family regulators. Database comparison revealed two hypothetical domains, a LuxR‐type helix‐turn‐helix (HTH) DNA binding motif near the C‐terminal and an N‐terminal nucleotide triphosphate (NTP) binding motif included. Deletion of the corresponding gene (ECO‐orf4) resulted in complete loss of ECO‐0501 production. Complementation by one copy of intact ECO‐orf4 restored the polyene biosynthesis demonstrating that ECO‐orf4 is required for ECO‐0501 biosynthesis. The results of overexpression ECO‐orf4 on ECO‐0501 production indicated that it is a positive regulatory gene. Gene expression analysis by reverse transcription PCR of the ECO‐0501 gene cluster showed that the transcription of ECO‐orf4 correlates with that of genes involved in polyketide biosynthesis. These results demonstrated that ECO‐orf4 is a pathway‐specific positive regulatory gene that is essential for ECO‐0501 biosynthesis.