RESUMO
This paper presents studies on an ultrastructural analysis of plant tissue infected with different pathotypes of Pepino mosaic virus (PepMV) and the immunolocalization of viral coat proteins. Because the PepMV virus replicates with a high mutation rate and exhibits significant genetic diversity, therefore, isolates of PepMV display a wide range of symptoms on infected plants. In this work, tomato plants of the Beta Lux cultivar were inoculated mechanically with three pathotypes representing the Chilean 2 (CH2) genotype: mild (PepMV-P22), necrotic (PepMV-P19) and yellowing (PepMV-P5-IY). The presence of viral particles in all infected plants in the different compartments of various cell types (i.e. spongy and palisade mesophyll, sieve elements and xylem vessels) was revealed via ultrastructural analyses. For the first time, it was possible to demonstrate the presence of crystalline inclusions, composed of virus-like particles. In the later stage of PepMV infection (14 dpi) various pathotype-dependent changes in the structure of the individual organelles (i.e. mitochondria, chloroplasts) were found. The strongest immunogold labeling of the viral coat proteins was also observed in plants infected by necrotic isolates. A large number of viral coat proteins were marked in the plant conductive elements, both xylem and phloem.
Assuntos
Vírus do Mosaico , Doenças das Plantas/virologia , Solanum lycopersicum/ultraestrutura , Solanum lycopersicum/virologia , Proteínas do Capsídeo/ultraestrutura , Chile , Imuno-Histoquímica , Solanum lycopersicum/citologia , Vírus do Mosaico/química , Vírus do Mosaico/patogenicidade , Vírus do Mosaico/ultraestrutura , Folhas de Planta/ultraestrutura , Folhas de Planta/virologia , Potexvirus/química , Potexvirus/ultraestrutura , VirulênciaRESUMO
The complete nucleotide sequence of the genomes of two Spanish isolates (LE-2000 and LE-2002) from tomato and one Peruvian isolate (LP-2001) from Lycopersicon peruvianum of the Pepino mosaic virus (PepMV) were determined. The tomato isolates share identities higher than 99%, while the genome of LP-2001 had mean nucleotide identities of 95.6% to 96.0% with tomato isolates. The predicted amino acid sequences showed similarities ranging between 95.2% and 100% with TGBp3 and TGBp2 and CP proteins, respectively. In LP-2001 two main differences were found with respect to the tomato isolates; (i) the 5' untranslated region (UTR) was 2 nt shorter by deletion at position 12-13 and it had some polymorphims at the putative promoter sequence reported for PepMV tomato isolates and other potexviruses, which could be functionally significant for RNA replication, and (ii) the TGBp3 protein had two extra amino acids in the C-terminal region.