Association of aster yellows subgroup 16SrI-C phytoplasmas with a disease of Ribes rubrum

Abstract A Ribes rubrum plant showing malformation and twisting of branches was found in a private garden in South Bohemia. Observation of ultrathin sections of tissues from symptomatic shoots revealed the presence of phytoplasma-like bodies. Different primer sets were used for amplification of the 16S-23S ribosomal gene segment. RFLP analysis and sequencing for phytoplasma identification classified the detected phytoplasma in the aster yellows group, subgroup 16SrI-C. Successful transmission of detected phytoplasma by dodder (Cuscuta campestris Yuncker) to periwinkle (Catharanthus roseus L.) was confirmed by detection of numerous phytoplasma bodies in ultrathin sections of C. roseus and by PCR from dodder and periwinkle. RFLP analyses of PCR products as well as nucleotide sequences of the currant plant and symptomatic periwinkles were identical. Sequenced data obtained from both currant and indicator plant, were aligned and sequences of 1,613 bp were found to be identical. Transmissions of phytoplasma by grafting to healthy currant rootstocks were unsuccessful

Chrysoviruses Inhabited Symbiotic Fungi of Lichens

A lichen body is formed most often from green alga cells trapped in a net of ascomycetous fungi and accompanied by endolichenic or parasitic fungi, other algae, and symbiotic or free-living bacteria. The lichen’s microcosmos is inhabited by mites, insects, and other animals for which the lichen is a source of food or a place to live. Novel, four-segmented dsRNA viruses were detected in saxicolous Chrysothrix chlorina and Lepraria incana lichens. Comparison of encoded genome proteins revealed classification of the viruses to the genus Alphachrysovirus and a relationship to chrysoviruses from filamentous ascomycetous fungi. We propose the names Chrysothrix chrysovirus 1 (CcCV1) and Lepraria chrysovirus 1 (LiCV1) as acronyms for these viruses. Surprisingly, observation of Chrysothrix chlorina hybridization with fluorescent-labelled virus probe by confocal microscope revealed that the CcCV1 virus is not present in the lichen body-forming fungus but in accompanying endolichenic Penicillium citreosulfuratum fungus. These are the first descriptions of mycoviruses from a lichen environment

Universal primers for plasmid detection and method for their relative quantification in phytoplasma-infected plants

Abstract Rep gene occurring in the majority of plasmids associated with phytoplasmas was selected as a target for real-time PCR together with single-copy Tuf gene from the phytoplasma genome. Rep-specific primers amplified products from host plants infected with phytoplasmas of groups 16SrI, -II, -III, -V, -X, and -XII. Relative concentrations of plasmids ranged depending on strain from 1-2 copies to several hundred copies per each phytoplasma studied. Primers targeting the rep gene are proposed for direct PCR detection of phytoplasma plasmids from experimental periwinkle host as well as from natural plant hosts

Platinum anniversary: virus and lichen alga together more than 70 years.

Trebouxia aggregata (Archibald) Gärtner (phylum Chlorophyta, family Trebouxiaceae), a lichen symbiotic alga, has been identified as host of the well-known herbaceous plant virus Cauliflower mosaic virus (CaMV, family Caulimoviridae). The alga had been isolated from Xanthoria parietina more than 70 years ago and has been maintained in a collection since that time. The CaMV detected in this collection entry has now been completely sequenced. The virus from T. aggregata is mechanically transmissible to a herbaceous host and induces disease symptoms there. Its genome differs by 173 nt from the closest European CaMV-D/H isolate from cauliflower. No site under positive selection was found on the CaMV genome from T. aggregata. We therefore assume that the virus's presence in this alga was not sufficiently long to fix any specific changes in its genome. Apart from this symbiotic alga, CaMV capsid protein sequences were amplified from many other non-symbiotic algae species maintained in a collection (e.g., Oonephris obesa, Elliptochloris sp., Microthamnion kuetzingianum, Chlorella vulgaris, Pseudococcomyxa sp.). CaMV-free Chlorella vulgaris was treated with CaMV to establish virus infection. The virus was still detected there after five passages. The virus infection is morphologically symptomless on Chlorella algae and the photosynthesis activity is slightly decreased in comparison to CaMV-free alga culture. This is the first proof as to the natural presence of CaMV in algae and the first demonstration of algae being artificially infected with this virus

Lichens-a new source or yet unknown host of herbaceous plant viruses?

Abstract Lichens are symbiotic associations of fungi with green algae or cyanobacteria. They have arisen independently several times within the Ascomycota and Basidiomycota. This symbiosis became with time one of the most successful life forms on Earth. Outside of the symbiotic algae and fungi, there are endophytic fungi, other algae, and lichen-associated bacteria present within lichen thalli. Till now, no lichen-specific pathogens have been reported among bacteria and viruses. Around 15 dsRNA viruses are known from Eurotiomycetes and another dsRNA and reverse transcribed ssRNA viruses from Dothideomycetes containing some lichenized fungal lineages. Algal viruses have been identified from less than 1 % of known eukaryotic algal species but no virus has been found in Trebouxia or in Trentepohlia (Chlorophyta, Pleurastrophyceae, Pleurastrales), the most common green lichen photobionts. On the other hand, dsDNA viruses infecting related Chlorella algae are well known from freshwater phytoplankton. However, high-molecular weight dsRNA isolated from different lichen thalli indicated to us presence of ss or dsRNA viruses. A PCRbased search for viruses with genus-specific and speciesspecific primers resulted in amplification of genome segments highly identical with those of plant cytorhabdoviruses and with Apple mosaic virus (ApMV). The nucleotide sequence of the putative lichen cytorhabdovirus showed high identity (98 %) with Ivy latent cytorhabdovirus. The nucleotide sequences of six Apple mosaic virus isolates from lichens showed high similarity with ApMV isolates from apple and pear hosts. The lichen ApMV isolates were mechanically transmitted to an herbaceous host and detected positive in ELISA 14 days thereafter, which support its infectivity on plants. We prepared axenic cultures of photobionts identified as Trebouxia sp. from this ApMVpositive lichen samples. All these cultures were positive for ApMV in RT-PCR test. We suggest that lichens as a whole (or their photobionts, more specifically) could serve as reservoirs for viruses, despite the fact that the way of transmission between different organisms is not Eur J Plant Patho