Identidade e propriedades de isolados de potyvírus provenientes de Capsicum spp

Translationally controlled tumour protein (TCTP) from tomato and Nicotiana benthamiana is necessary for successful infection by a potyvirus

Translationally controlled tumour protein (TCTP) is a ubiquitously distributed protein in eukaryotes, involved in the regulation of several processes, including cell cycle progression, cell growth, stress protection, apoptosis and maintenance of genomic integrity. Its expression is induced during the early stages of tomato (Solanum lycopersicum) infection by the potyvirus Pepper yellow mosaic virus (PepYMV, a close relative of Potato virus Y). Tomato TCTP is a protein of 168 amino acids, which contains all the conserved domains of the TCTP family. To study the effects of TCTP silencing in PepYMV infection, Nicotiana benthamiana plants were silenced by virus-induced gene silencing (VIGS) and transgenic tomato plants silenced for TCTP were obtained. In the early stages of infection, both tomato and N. benthamiana silenced plants accumulated less virus than control plants. Transgenic tomato plants showed a drastic reduction in symptoms and no viral accumulation at 14 days post-inoculation. Subcellular localization of TCTP was determined in healthy and systemically infected N. benthamiana leaves. TCTP was observed in both the nuclei and cytoplasm of non-infected cells, but only in the cytoplasm of infected cells. Our results indicate that TCTP is a growth regulator necessary for successful PepYMV infection and that its localization is altered by the virus, probably to favour the establishment of virus infection. A network with putative interactions that may occur between TCTP and Arabidopsis thaliana proteins was built. This network brings together experimental data of interactions that occur in other eukaryotes and helps us to discuss the possibilities of TCTP involvement in viral infection.

Inheritance of resistance to Pepper yellow mosaic virus in Capsicum baccatum var. pendulum

We investigated inheritance of resistance to Pepper yellow mosaic virus (PepYMV) in Capsicum baccatum var. pendulum accessions UENF 1616 (susceptible) crossed with UENF 1732 (resistant). Plants from generations P1, P2, F1, F2, BC1:1, and BC1:2 were inoculated and the symptoms were evaluated for 25 days. Subsequently, an area under the disease progress curve was calculated and subjected to generation means analysis. Only the average and epistatic effects were significant. The broad and narrow sense heritability estimates were 35.52 and 21.79%, respectively. The estimate of the minimum number of genes that control resistance was 7, indicating that resistance is polygenic and complex. Thus, methods to produce segregant populations that advocate selection in more advanced generations would be the most appropriate to produce chili pepper cultivars resistant to PepYMV.

Complete genome sequence of pepper yellow mosaic virus, a potyvirus, occurring in Brazil

The complete genomic sequence of pepper yellow mosaic virus (PepYMV), a member of the genus Potyvirus, was determined. The sequence was 9745 nucleotides long, excluding the 3' poly(A) tail. The genome contained a large open reading frame encoding a polyprotein of 3085 amino acids, which contained the typically conserved motifs found in members of the genus Potyvirus and an additional P3-PIPO (pretty interesting potyvirus ORF). In a pairwise comparison with other potyvirus sequences, the full genome of PepYMV shared a maximum of 63.84 % nucleotide sequence identity with pepper mottle virus (PepMoV), followed by verbena virus Y (VVY, 62.11 %), potato virus Y (PVY, 62.07 %) and Peru tomato mosaic virus (PTV, 62.00 %). Based upon a phylogenetic analysis, PepYMV was most closely related to PepMoV and PTV, within the PVY subgroup cluster, like most potyviruses isolated in solanaceous hosts in South America.

Genome-wide analysis of differentially expressed genes during the early stages of tomato infection by a potyvirus

Plant responses against pathogens cause up- and downward shifts in gene expression. To identify differentially expressed genes in a plant-virus interaction, susceptible tomato plants were inoculated with the potyvirus Pepper yellow mosaic virus (PepYMV) and a subtractive library was constructed from inoculated leaves at 72 h after inoculation. Several genes were identified as upregulated, including genes involved in plant defense responses (e.g., pathogenesis-related protein 5), regulation of the cell cycle (e.g., cytokinin-repressed proteins), signal transduction (e.g., CAX-interacting protein 4, SNF1 kinase), transcriptional regulators (e.g., WRKY and SCARECROW transcription factors), stress response proteins (e.g., Hsp90, DNA-J, 20S proteasome alpha subunit B, translationally controlled tumor protein), ubiquitins (e.g., polyubiquitin, ubiquitin activating enzyme 2), among others. Downregulated genes were also identified, which likewise display identity with genes involved in several metabolic pathways. Differential expression of selected genes was validated by macroarray analysis and quantitative real-time polymerase chain reaction. The possible roles played by some of these genes in the viral infection cycle are discussed.