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V Pallás

Publications and source records attributed to V Pallás.

23 records · Page 2Linked to original sources
PubMed1994

Nucleotide sequence of apple mosaic ilarvirus RNA 4.

The complete nucleotide sequence of apple mosaic ilavirus RNA 4 was obtained from cloned cDNAs and direct sequencing of the 5'-terminal RNA region. The sequence is 891 nucleotides long and can encode a protein of 226 amino acids (M(r) 25,171) that, by analogy to alfalfa mosaic virus (AlMV) and tobacco streak virus (TSV), should correspond to the coat protein (CP). Database comparisons showed that no significant similarity to other proteins was apparent. Analysis of the CP sequence revealed a putative 'zinc finger' domain and a region rich in basic residues at the amino-terminal portion of the protein, similar to that of TSV. The secondary structure proposed for the 3'-terminal region of RNA 4 shows the presence of three hairpin structures flanked by the tetranucleotide AUGC that are highly similar to those previously described in the RNA 4 species from AlMV and TSV. These results support the idea that both features (metal-binding domain and highly conserved hairpin structures) are characteristics of ilarviruses and are probably involved in the peculiar 'genome activation' phenomenon described in these viruses.

Amino Acid Sequence↗
PubMed1993

Chemiluminescent and colorigenic detection of cherry leaf roll virus with digoxigenin-labeled RNA probes.

Digoxigenin-labeled RNA probes were used to detect cherry leaf roll virus in infected plants. A dot-blot hybridization immunoenzymatic assay in both crude sap extracts and partially purified tissue with a colorigenic and chemiluminescent detection was developed. The use of the new AMPPD substrate was found to be effective in clarified sap extracts in conditions were the colorigenic detection method failed. Both detection assays were effective when using unfractionated nucleic acid preparations, the chemiluminescent being five times more sensitive than the colorigenic. The chemiluminescent hybridization assay makes it possible to detect the virus at the picogram level. The non-radioactive dot-blot hybridization techniques described here turned out to be very suitable for plant virus diagnosis. The sensitivity of this method and those obtained by ELISA or radioactive dot-blot described previously is compared.

Blotting, Northern↗
PubMed1989

Interactions between citrus exocortis and potato spindle tuber viroids in plants of Gynura aurantiaca and Lycopersicon esculentum.

Plants of Gynura aurantiaca and tomato (Lycopersicon esculentum) were inoculated with severe strains of citrus exocortis viroid (CEV) and potato spindle tuber viroid (PSTV). The progeny of both viroids was analyzed by two systems of PAGE which allowed discrimination between CEV and PSTV on the basis of their different sizes. When inoculated separately to G. aurantiaca CEV and PSTV induced severe and very mild symptoms, respectively, with CEV accumulating to a higher level than PSTV, whereas when tomato was the host, each viroid induced severe symptoms (although the reaction caused by PSTV was more intense) with PSTV reaching a higher steady-state concentration than CEV. The simultaneous inoculation of both viroids induced in G. aurantiaca the characteristic symptomatology of CEV, which was the only viroid that could be detected, whereas the response observed in tomato was that typical of PSTV, and only this viroid could be recovered. On the other hand, when G. aurantiaca plants were first inoculated with PSTV and later challenged with CEV, part of the plants displayed the characteristic severe reaction of CEV and both viroids were present in the corresponding extracts, but the other part showed the mild symptomatology induced by PSTV, and only this viroid could be isolated. However, when the protected plants were topped the new shoots exhibited severe symptoms and only CEV could be detected. These results suggest that CEV and PSTV compete for a limiting host factor needed for their replication, transport or accumulation, with CEV and PSTV having the highest affinity for the G. aurantiaca and tomato factors, respectively.

Electrophoresis, Polyacrylamide Gel↗
PubMed1987

The sequence of a viroid from grapevine closely related to severe isolates of citrus exocortis viroid.

The primary structure of a grapevine viroid (GVs) isolated in Spain was determined. The sequence consisted of 369 nucleotide residues forming a circular molecule. GVs presented extensive homology with viroids of the potato spindle tuber viroid (PSTV) group, that was specially high in the case of citrus exocortis viroid (CEV) both with variants found in isolates inducing severe (92% with CEV-A) and mild (89% with CEV-DE26) symptoms on tomato. The secondary structure proposed for GVs showed that the changes in the sequence in relation to CEV-A generated modifications of the secondary structure particularly important in the left terminal (Tl), variable (V) and pathogenesis (P) viroid domains that have been postulated. Nevertheless it was noted in GVs a central core in the P domain that is conserved in the class A sequence variants characteristic of severe isolates, but not in the class B ones found in mild isolates of CEV. These observations indicate that GVs should be considered as a severe isolate of CEV from grapevine (CEV-g), a suggestion that correlates with the biological properties of CEV-g both in tomato and in Gynura aurantiaca. The presence of this central core in the P domain seems to characterize all the variants of CEV inducing severe symptoms in tomato.

Citrus↗