Konjak mosaic virus: the complete nucleotide sequence of the genomic RNA and its comparison with other potyviruses

A new potyvirus first isolated and identified from Angelica sinensis

A filamentous virus was isolated in Angelica sinensis (Angelica sinensis (Oliv.) Diels) which shows mosaic symptoms on leaves in Minxian, Gansu province, China. According to morphology and molecular biology properties, this virus, which has a flexuous rod-shaped particle about 750 nm in length and 12 nm in width, was assigned to the genus Potyvirus, family Potyviridae. Its coat protein (CP) shows high similarity with six other potyviruses by analysis of peptide mass fingerprinting (PMF). The 919 bp nucleotides of 3' terminal covering partial CP gene and 3'-untranslated region was amplified by RT-PCR using degenerate primers which were designed according to the result of PMF. In sequence comparisons and phylogenetic analysis, the new isolate was found to be closely related to Japanese hornwort mosaic virus (JHMV), Konjak mosaic virus (KoMV), and Zantedeschia mosaic virus (ZaMV). The most closely related virus is JHMV03 (AB251346), with 96.59% aa and 87.60% nt identity to the isolate. All results suggest the presence of a new member of potyvirus, tentatively named Dang Gui strain of Japanese hornwort mosaic virus (JHMV-DG*). In our research the antiserum against the CP of JHMV-DG had also been prepared. To our knowledge, it is the first time that a potyvirus has been isolated and identified in Angelica sinensis.

Recombination and gene duplication in the evolutionary diversification of P1 proteins in the family Potyviridae

Genome structure and sequence are notably conserved between members of the family Potyviridae. However, some genomic regions of these viruses, such as that encoding the P1 protein, show strikingly high variability. In this study, some partially conserved motifs were identified upstream of the quite well-conserved protease domain located near the P1 C terminus. The irregular distribution of these motifs suggests that the potyviral P1 proteins have undergone complex evolutionary diversification. Evidence was found of recombination events in the P1 N-terminal region, similar to those reported in potyviruses of the bean common mosaic virus subgroup, but also affecting other potyviruses. Moreover, intergeneric recombination events affecting potyviruses and ipomoviruses were also observed. Evidence that these recombination events could be linked to host adaptation is provided. Specific sequence features and differences in net charge help to classify the P1 proteins of members of the family Potyviridae into two groups: those from potyviruses and rymoviruses and those from tritimoviruses. The ipomovirus Cucumber vein yellowing virus has two P1 copies arranged in tandem, the most N-terminal one being of the potyvirus type and the other being of the tritimovirus type. These findings suggest that both recombination and gene duplication have contributed to P1 evolution and helped to facilitate successful adaptation of members of the family Potyviridae to a wide range of host species.