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The effect was studied of the fungal cyclodepsipeptide antibiotics beauvericin and seven distinct enniatins on acyl-CoA: cholesterol acyltransferase (ACAT) activity. In an enzymeassay using rat liver microsomes, all the compounds were found to inhibit ACATactivity. The drug concentration that caused 50%inhibition (IC50 value) of the enzyme activity was determined to be 3.0/jm for beauvericin, indicating that the compoundis one of the most potent ACATinhibitors of microbial origin. Enniatins exhibited much higher IC50 values of 22 to 1 10/xm. More hydrophobic enniatins showed more potent inhibitory activity. Furthermore, the ACATinhibitory activity was evaluated as inhibition of cholesteryl ester formation in a cell assay using J774 macrophages. Calculation of the ratio, CD50 value (the drug concentration causing 50% cell damage)/IC50 value of cholesteryl ester formation, indicated that beauvericin shows the highest specificity. These data indicate that beauvericin is one of the most potent and specific ACATinhibitors of microbial origin.Acyl-CoA: cholesterol acyltransferase (ACAT) [EC 2.3. 1.26], which catalyzes the conversion of cellular cholesterol and long chain fatty acyl-CoA to cholesteryl ester, plays an important role in cholesteryl ester accumulation in atherogenesis1} and in cholesterol absorption from intestines2). Since elevated levels of plasma cholesterol is a well-documented risk factor of atherosclerosis, much attention has been paid to ACATinhibitors for the treatment and prevention of atherosclerosis and hypercholesterolemia.A lot of synthetic ACATinhibitors have been reported having a urea or an amide moiety. Wehave started to find new ACATinhibitors and new lead compounds of microbial origin. During our screening program, fungal strains Fusarium spp. FO-740 and FO-1305 were found to produce ACATinhibitors. The active compounds were identified as beauvericin (Fig. 1) from the former strain and seven components of enniatins (A, Al, B, Bl, D, E and F, Fig. 1) from the latter strain3). All of these cyclodepsipeptides were classified as ionophore antibiotics, most of which were originally reported as antifungal or insecticidal antibiotics produced by Beauveria4' 5\ Paecilomyces6\ Fusarium1' 8) and Polyporus^spp. However, it is not clearly understood whether these biological activities are due to the ionophoric activity.The cyclodepsipeptides were found by the authors to show a new biological activity of ACAT inhibition3*.In this study, we have examined the effect of beauvericin and enniatins on cholesterol

Turnip mosaic virus (TuMV, genus Potyvirus, family Potyviridae) infects mainly cruciferous plants. Isolates Tu-3 and Tu-2R1 of TuMV exhibit different infection phenotypes in cabbage (Brassica oleracea L.) and Japanese radish (Raphanus sativus L.). Infectious full-length cDNA clones, pTuC and pTuR1, were constructed from isolates Tu-3 and Tu-2R1, respectively. Progeny virus derived from infections with pTuC induced systemic chlorotic and ringspot symptoms in infected cabbage, but no systemic infection in radish. Virus derived from plants infected with pTuR1 induced a mild chlorotic mottle in cabbage and infected radish systemically to induce mosaic symptoms. By exchanging genome fragments between the two virus isolates, the P3-coding region was shown to be responsible for systemic infection by TuMV and the symptoms it induces in cabbage and radish. Moreover, exchanges of smaller parts of the P3 region resulted in recombinants that induced complex infection phenotypes, especially the combination of pTuC-derived N-terminal sequence and pTuR1-derived C-terminal sequence. Analysis by tissue immunoblotting of the inoculated leaves showed that the distributions of P3-chimeric viruses differed from those of the parents, and that the origin of the P3 components affected not only virus accumulation, but also long-distance movement. These results suggest that the P3 protein is an important factor in the infection cycle of TuMV and in determining the host range of this and perhaps other potyviruses.

Cucurbits are grown throughout the North-West Frontier Province of Pakistan as summer and winter crops. Plants having mosaic, mottling, chlorosis and leaf distortion symptoms were frequently found in most of the cucurbit fields during the survey. Using dot immunobinding assay, Cucumber green mottle mosaic virus (CGMMV), Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV) and Papaya ringspot virus (PRSV) were found infecting cucurbits. CGMMV was widespread, infecting 46.9% of the samples tested followed by ZYMV (14.8%), WMV (12.5%) and PRSV (7.8%). Multiple infections were common with 42% of the samples being infected with two viruses and 8% with three viruses. The nucleotide sequences of the coat protein (CP) genes of these four viruses were determined and deduced amino acid sequence comparisons revealed 88.3-99% similarity of the ZYMV-Pak isolate with other isolates of ZYMV reported worldwide. The amino acid sequence identity of Pakistani isolates of WMV, CGMMV and PRSV ranged from 96.8 to 98.4%, 98.1 to 99.4% and 79.3 to 84.2%, respectively, with other isolates reported elsewhere. Little variability was observed in the sequences of WMV and CGMMV. ZYMV-Pak was very close to the USA isolate, and the PRSV-Pak isolate was close to Indian isolates of PRSV possibly reflecting the geographical relationship between these isolates.

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