Characterization of Cucurbit Aphid-Borne Yellows Virus (CABYV) from Passion Fruit in Brazil: Evidence of a Complex of Species within CABYV Isolates.

High-throughput sequencing (HTS) has been an important tool for the discovery of plant viruses and their surveillance. In 2015, several virus-like symptoms were observed in passion fruit (PF) plants in Bahia state, Brazil. Using HTS technology, bioinformatics tools, RT-PCR, and Sanger sequencing, we identified the cucurbit aphid-borne yellows virus (CABYV, Polerovirus, Solemoviridae) in co-infection with cowpea aphid-borne mosaic virus (CABMV, Potyvirus, Potyviridae) in PF, in green manure, and spontaneous plants in several localities in Bahia. Complete genomes of CABYV-PF isolates were determined and analyzed with other CABYV isolates available in GenBank that have been identified in various countries. Phylogenetic analysis and pairwise identity comparison with CABYV isolates showed that CABYV-PFs are more closely related to French and Spanish isolates. Overall, analyses of all the CABYV genomes revealed that these could represent ten distinct species, and we thus proposed reclassifying these CABYV as isolates into ten species, tentatively named "Polerovirus curcubitaeprimum" to "Polerovirus curcubitaenonum", and "Polerovirus melo". CABYV-PF is a member of "Polerovirus curcubitaeprimum".

A Capsid Protein Fragment of a Fusagra-like Virus Found in Carica papaya Latex Interacts with the 50S Ribosomal Protein L17.

Papaya sticky disease is caused by the association of a fusagra-like and an umbra-like virus, named papaya meleira virus (PMeV) and papaya meleira virus 2 (PMeV2), respectively. Both viral genomes are encapsidated in particles formed by the PMeV ORF1 product, which has the potential to encode a protein with 1563 amino acids (aa). However, the structural components of the viral capsid are unknown. To characterize the structural proteins of PMeV and PMeV2, virions were purified from Carica papaya latex. SDS-PAGE analysis of purified virus revealed two major proteins of ~40 kDa and ~55 kDa. Amino-terminal sequencing of the ~55 kDa protein and LC-MS/MS of purified virions indicated that this protein starts at aa 263 of the deduced ORF1 product as a result of either degradation or proteolytic processing. A yeast two-hybrid assay was used to identify Arabidopsis proteins interacting with two PMeV ORF1 product fragments (aa 321-670 and 961-1200). The 50S ribosomal protein L17 (AtRPL17) was identified as potentially associated with modulated translation-related proteins. In plant cells, AtRPL17 co-localized and interacted with the PMeV ORF1 fragments. These findings support the hypothesis that the interaction between PMeV/PMeV2 structural proteins and RPL17 is important for virus-host interactions.

Development of methodologies for virus detection in soybean and wheat seeds.

Seeds that contain large amounts of oil, starch, fibers and phenols are the most difficult tissues for RNA extraction. Currently, there are some reports of virus detection in seeds using commercial kits for RNA extraction. However, individual seeds were used, which may not be always suitable for analyses that deal with large amounts of seeds. Sangha [1] described a simple, quick and efficient protocol for RNA extraction and downstream applications in a group of seeds of jatropha (Jatropha curcas), mustard (Brassica sp.) and rice (Oryza sativa). We tested this protocol for soybean (Glycine max), maize (Zea mays), wheat (Triticum aestivum) and triticale (×Triticosecale) seeds and further reverse transcription PCR (RT-PCR)/quantitative real-time PCR (qPCR) in order to have a faster and more practical method for virus detection from seeds than the traditional scheme of seed planting and subsequent Elisa/RT-PCR from leaves. The essential points in the method are:•Some modifications in the protocol [1] were done in order to increase performance: Wheat and triticale seeds are incubated with water prior to maceration. An amount of 1.2 g of dry soybean seeds is used to maceration.•RT-PCR is used for detection of Wheat streak mosaic virus from wheat seeds and RT-qPCR for detection of Soybean mosaic virus from soybean seeds.•The method may be tested for other viruses, however, pre-validation will be needed.