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Potato Yellow Vein Virus (PYVV) threatens potato production in South America. Visual field monitoring is commonly used to detect PYVV on potato crops but the disease is generally detected only after significant damage has occurred to photosynthetic tissues. Therefore, a method for detecting the disease before yields are severely affected would be useful. Remotely sensed multispectral reflectance, based on the reflectivity and propagation of light radiation inside plant tissues, was tested for the detection of PYVV infection in potato plants grown indoors. A visual assessment of disease symptoms in both virus-infected and virus-free plants was compared to monitoring based on spectroradiometry and multispectral photographic images of the same plants, recorded during their growth and development. Results showed that changes in reflectance in certain regions of the electromagnetic spectrum, indicative of disturbances in light reflection by vascular tissues in infected plants, measured with an spectroradiometer, as well as derived spectral Vegetation Indices such as NDVI, SAVI, and IPVI, provide early detection of viral infection, long before symptoms of chlorosis can be detected by the trained eye. [ABSTRACT FROM AUTHOR]

Abstract: We have cloned and characterized mRNAs corresponding to the phosphoprotein (P) and nucleocapsid (N) genes of the sanguinolenta strain of Potato yellow dwarf virus (PYDV). The P and N messenger RNAs both begin with a common AAACA pentanucleotide and are 1546nt and 962nt in length, and capable of encoding 52kDa and 31kDa proteins, respectively. The N mRNA contains a 12nt 5′ non-translated sequence (NTS) and a 83nt 3′-NTS. Similarly, the P mRNA has a 19nt 5′-NTS and a 125nt 3′-NTS. Primary structure analyses revealed three potential phosphorylation sites in the P protein and six in the N protein. Despite a lack of predictable nuclear localization signals (NLSs) in either protein, transient expression of the P and N proteins in N. benthamiana showed that both proteins are targeted exclusively to nuclei. Phylogenetic analyses showed that PYDV is most closely related to Maize mosaic virus and Taro vein chlorosis virus, which also lack predictable NLSs in their N proteins. The present data further distinguish PYDV from SYNV and suggest that, together, these viruses serve to provide a more comprehensive view of rhabdovirus cell biology, which can be studied in a common host plant. [Copyright &y& Elsevier]

RNAs of many viruses are translated efficiently in the absence of a 5' cap structure. The tobacco necrosis virus (TNV) genome is an uncapped, nonpolyadenylated RNA whose translation mechanism has not been well investigated. Computational analysis predicted a cap-independent translation element (TE) within the 3' untranslated region (3' UTR) of TNV RNA that resembles the TE of barley yellow dwarf virus (BYDV), a luteovirus. Here we report that such a TE does indeed exist in the 3' UTR of TNV strain D. Like the BYDV TE, the TNV TE (i) functions both in vitro and in vivo, (ii) requires additional sequence for cap-independent translation in vivo, (iii) has a similar secondary structure and the conserved sequence CGGAUCCUGGGAA ACAGG, (iv) is inactivated by a four-base duplication in this conserved sequence, (v) can function in the 5' UTR, and (vi) when located in its natural 3' location, may form long-distance base pairing with the viral 5' UTR that is conserved and probably required. The TNV TE differs from the BYDV TE by having only three helical domains instead of four. Similar structures were found in all members of the Necrovirus genus of the Tombusviridae family, except satellite tobacco necrosis virus, which harbors a different 3' cap-independent translation domain. The presence of the BYDV-like TE in select genera of different families indicates that phylogenetic distribution of TEs does not follow standard viral taxonomic relationships. We propose a new class of cap-independent TE called BYDV-like TE. [ABSTRACT FROM AUTHOR]