A bioassay-guided isolation using a green fluorescence protein (GFP)-tagged pepper mottle virus (PepMoV-GFP) based leaf-disk method to obtain new antiviral agents led to the isolation of trichodermin, 1, and a new compound trichoderminol, 2, from EtOAc extract of Trichoderma albolutescens culture medium. The structures of compounds 1 and 2 were determined by MS and NMR experiments, and the absolute configurations of the compounds were established by experimental and calculated vibrational circular dichroism spectra. Compounds 1 and 2 were evaluated for their anti-PepMoV potential in systemic host plants, such as tobacco and pepper, by PepMoV-GFP based systemic host method. All compounds exhibited inactivation effects against PepMoV. Furthermore, compound 1 showed protective effects against PepMoV.
Plant-virus-based expression vectors have been used as an alternative to the creation of transgenic plants. Using a virus-based vector, we investigated the feasibility of producing the endoglucanase D (EngD) from Clostridium cellulovorans in Nicotiana benthamiana. This protein has endoglucanase, xylanase, and exoglucanase activities and may be of value for cellulose digestion in the generation of biofuels from plant biomass. The EngD gene was cloned between the nuclear inclusion b (NIb)- and coat protein (CP)-encoding sequences of pSP6PepMoV-Vb1. In vitro transcripts derived from the clone (pSP6PepMoV-Vb1/EngD) were infectious in N. benthamiana but caused milder symptoms than wild-type PepMoV-Vb1. RT-PCR amplification of total RNA from non-inoculated upper leaves infected with PepMoV-Vb1/EngD produced the target band for the CP, partial NIb and EngD-CP regions of PepMoV-V1/EngD, in addition to nonspecific bands. Western blot analysis showed the CP target bands of PepMoV-Vb1/EngD as well as non-target bands. EngD enzymatic activity in infected plants was detected using a glucose assay. The plant leaves showed increased senescence compared with healthy and PepMoV-Vb1-infected plants. Our study suggests the feasibility of using a viral vector for systemic infection of plants for expression of heterologous engD for the purpose of digesting a cellulose substrate in plant cells for biomass production.
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