Comparative analysis of rapamycin biosynthesis clusters between Actinoplanes sp. N902-109 and Streptomyces hygroscopicus ATCC29253.

The present study was designed to identify the difference between two rapamycin biosynthetic gene clusters from Streptomyces hygroscopicus ATCC29253 and Actinoplanes sp. N902-109 by comparing the sequence and organization of the gene clusters. The biosynthetic gene cluster for rapamycin in Streptomyces hygroscopicus ATCC29253 was reported in 1995. The second rapamycin producer, Actinoplanes sp. N902-109, which was isolated in 1995, could produce more rapamycin than Streptomyces hygroscopicus ATCC29253. The genomic map of Actinoplanes sp. N902-109 has been elucidated in our laboratory. Two gene clusters were compared using the online software anti-SMASH, Glimmer 3.02 and Subsystem Technology (RAST). Comparative analysis revealed that the organization of the multifunctional polyketide synthases (PKS) genes: RapA, RapB, RapC, and NRPS-like RapP were identical in the two clusters. The genes responsible for precursor synthesis and macrolactone modification flanked the PKS core region in N902-109, while the homologs of those genes located downstream of the PKS core region in ATCC29253. Besides, no homolog of the gene encoding a putative type II thioesterase that may serve as a PKS "editing" enzyme accounted for over-production of rapamycin in N902-109, was found in ATCC29253. Furthermore, no homologs of genes rapQ (encoding a methyltransferase) and rapG in N902-109 were found in ATCC29253, however, an extra rapM gene encoding methyltransferase was discovered in ATCC29253. Two rapamycin biosynthetic gene clusters displayed overall high homology as well as some differences in gene organization and functions.

Synthesis and antifungal activities of carabrol ester derivatives.

Thirty-eight new ester derivatives of carabrol were designed, synthesized, and characterized by (1)H and (13)C NMR and HR-ESI-MS. Their antifungal activities against the fungal pathogen Colletotrichum lagenarium were evaluated using a spore germination assay. Of these 38 ester derivatives, 16 showed higher antifungal activity than that of carabrol and 7 showed higher antifungal activity than that of carabrone. It was found that the C-4 position of carabrol was a key position involving its antifungal activity, which showed the variation of 50% inhibition concentration (IC(50)) from 2.70 to 52.33 µg/mL. When substituted by the phenyl ring, the ester derivatives with electron-attracting groups showed higher activity than those with electron-donating ones. Two ester derivatives, carabryl 4-cynaobenzoate (II-17, IC(50) 2.70 µg/mL) and carabryl 4-isopropylbenzoate (II-27, IC(50) 2.82 µg/mL), showed only slightly lower antifungal activity than that of the positive control chlorothalonil (IC(50) 0.87 µg/mL) and have been identified as promising leads for development of new environmentally friendly fungicides.