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Carvacrol expresses a wide range of biological activities, but the studies of its mechanisms focused on bacteria, mainly involving the destruction of the plasma membrane. In this study, carvacrol exhibited strong activities against several phytopathogenic fungi and demonstrated a novel antifungal mechanism against Lasiodiplodia theobromae. RNA sequencing indicated that many genes of L. theobromae hyphae were predominately induced by carvacrol, particularly those involved in replication and transcription. Hyperchromic, hypsochromic, and bathochromic effects in the UV-visible absorption spectrum were observed following titration of calf thymus DNA (ctDNA) and carvacrol, which indicated the formation of a DNA–carvacrol complex. Circular dichroism (CD) spectroscopy indicated that the response of DNA to carvacrol was similar to that of 4′,6-diamidino-2-phenylindole (DAPI) but different from that of ethidium bromide (EB), implying the ionic bonds between carvacrol and ctDNA. Fluorescence spectrum (FS) analysis indicated that carvacrol quenched the fluorescence of double-stranded DNA (dsDNA) more than single-stranded DNA, indicating that carvacrol mainly bound to dsDNA. A displacement assay showed that carvacrol reduced the fluorescence intensity of the DNA–DAPI complex through competition with DAPI, but this did not occur for DNA–EB. The FS assay revealed that carvacrol bound to the AAA sequence on the minor groove of ds-oligonucleotides. The hydroxyl of carvacrol was verified to bind to ctDNA through a comparative test in which structural analogs of carvacrol, including thymol and 4-ethyl-1,2-dimethyl, were analyzed. The current study indicated carvacrol can destruct plasma membranes and bind to the minor groove of DNA, inhibiting fungal proliferation by disturbing the stability of dsDNA. [ABSTRACT FROM AUTHOR]

Lasiodiplodia theobromae is a phytopathogenic fungus, which can cause many different diseases on different crops. The pathogen can cause leaf spot on tea plants (Camellia sinensis), which negatively affects the productivity and quality of tea leaves in tea plantations in Guizhou Province, China. Although the genome sequence of L. theobromae has been published, no data on the transcriptome or small RNA sequences of L. theobromae under in vitro conditions and the course of infection of tea leaf are available. Here, we report the high-quality transcriptome and small RNA sequences of L. theobromae in vitro conditions and the course of infection of tea leaf using the platform of Illumina HiSeq. This comprehensive expression profiling of the fungal pathogen will provide a valuable resource for future research on trait-specific genes of the pathogen, host-pathogen interactions, and disease resistance in the host. [ABSTRACT FROM AUTHOR]