Biological and serological variability, evolution and molecular epidemiology of Zucchini yellow mosaic virus (ZYMV, Potyvirus) with special reference to Caribbean islands

Zucchini yellow mosaic virus (ZYMV, Potyvirus) emerged as an important pathogen of cucurbits within the last 20 years. Its origins and mechanisms for evolution and worldwide spread represent important questions to understand plant virus emergence. Sequence analysis on a 250 nucleotide fragment including the N-terminal part of the coat protein coding region, revealed one major group of strains, and some highly divergent isolates from distinct origins. Within the major group, three subsets of strains were defined without correlation with geographic origin, year of collection or biological properties. ZYMV was first observed in Martinique and Guadeloupe in 1992 and 1994, respectively. We studied the evolution of ZYMV variability on both islands in the few years following the putative virus introduction. In Martinique, molecular divergence remained low even after 6 years, suggesting a lack of new introductions. Interactions between strains resulted in a stability of the high biological variability, while the serological diversity decreased and molecular divergence remained low. In Guadeloupe, as in Martinique in 1993, serological variability was high shortly after virus introduction. While the first introduction in Guadeloupe was independent from Martinique, the 'Martinique' type was detected in 1998, suggesting further introductions, maybe through viruliferous aphids or imported plant material.     

Spontaneous rupture of Achilles tendon and Cushing's disease. Case report

Spontaneous rupture of Achilles tendon is observed in patients with tumors, metabolic disorders, infections and systemic diseases. Fluoroquinolones may cause tendinopathies. In addition, spontaneous rupture uncommonly occurs in Cushing's syndrome. We report a case of Cushing's disease revealed by recurrent rupture of Achilles tendon. Tendon tears are described in patients receiving long-term steroid treatment, probably via a mechanism similar to that one occurring in Cushing's syndrome. Although exceptional, this diagnosis should be discussed in patients with spontaneous rupture of Achilles tendon.     

Characterization of the complete mitochondrial genome for the <Emphasis Type="Italic">Euphractus sexcinctus flavimanus</Emphasis> (Mammalia,Xenarthra) subspecies

We are reporting the complete mitochondrial genome for the Euphractus sexcinctus flavimanus, a subspecies from South America, who is also known as yellow armadillo and six-banded armadillo. The de novo short read assembly was obtained from a west-central Brazil specimen. A typical mammalian mitogenome, containing 37 genes and one non-coding region (D-loop) was found. The total length was 16,805 base pairs and differences were observed among the E. s. flavimanus mitogenome described here and that previously reported for an E. sexcinctus unknown subspecies. Such difference was mainly due to the variation in the non-coding region. The complete mitochondrial genome described for the E. s. flavimanus is an important data source for comparative approaches, including genetic diversity studies among armadillo species and subspecies.     

Association of an atypical alphasatellite with a bipartite New World begomovirus

The complete sequence of a watermelon-infecting Venezuelan begomovirus was obtained; it corresponds to that of the partially characterized melon chlorotic mosaic virus (MeCMV). MeCMV is a typical bipartite New World begomovirus. A putative alphasatellite, MeCMVa1, was found associated with MeCMV. This is the first satellite detected in the New World, and the first natural association of an alphasatellite with a bipartite begomovirus. The sequence of MeCMVa1 diverged highly from those of other alphasatellites, except for two atypical ones, which, like MeCMVa1, had a putative ORF2 embedded in the Rep-encoding ORF1. These findings raise new questions about the origin and evolution of subviral agents associated with begomoviruses.     

A novel natural mutation in HC-Pro responsible for mild symptomatology of Zucchini yellow mosaic virus (ZYMV, Potyvirus) in cucurbits

A natural mild isolate of Zucchini yellow mosaic virus was found to contain a mutation in the helper component (HC-Pro) within a conserved motif, “CDNQLD”, located 12 residues downstream from the “FRNK” motif involved in symptom severity. Introducing the mutation in an infectious cDNA clone of ZYMV resulted in an almost complete absence of symptoms, although viral accumulation was only partially reduced. The FRNK(X)₁₂CDNQLD sequence might be part of a larger motif that is conserved in potyviruses and plays a role in symptomatology and/or silencing inhibition.     

Reciprocal assistance for aphid transmission between non-transmissible strains of zucchini yellow mosaic potyvirus in mixed infections

Summary.  Several aphid non-transmissible strains of zucchini yellow mosaic potyvirus (ZYMV) have been described, in relation with mutations in the two viral proteins required for transmissibility, coat protein and helper component. Assistance mechanisms were previously shown to allow transmission of such strains when functional proteins are provided in trans. In this paper, we used monoclonal antibodies to allow a specific detection of two aphid non-transmissible strains of ZYMV and we revealed that reciprocal assistance mechanisms can mediate simultaneous aphid transmission of these deficient strains. Potential epidemiological and evolutive consequences of such assistance mechanisms between variants in complex virus populations are discussed. Received April 13, 1999 Accepted July 8, 1999     

The nucleotide sequence of <Emphasis Type="Italic">Watermelon mosaic virus</Emphasis> (WMV, <Emphasis Type="Italic">Potyvirus</Emphasis>) reveals interspecific recombination between two related potyviruses in the 5′ part of the genome

Summary. Watermelon mosaic virus (WMV, Potyvirus) is a potyvirus with a worldwide distribution, mostly in temperate and mediterranean regions. According to the partial sequences that were available, WMV appeared to share high sequence similarity with Soybean mosaic virus (SMV), and it was almost considered as a strain of SMV in spite of its different and much broader host range. Like SMV, it was also related to legume-infecting potyviruses belonging to the Bean common mosaic virus (BCMV) subgroup. In this paper we obtained the full-length sequence of WMV, and we confirmed that this virus is very closely related to SMV in most of its genome; however, there is evidence for an interspecific recombination in the P1 protein, as the P1 of WMV was 135 amino-acids longer than that of SMV, and the N-terminal half of the P1 showed no relation to SMV but was 85% identical to BCMV. This suggests that WMV has emerged through an ancestral recombination event, and supports the distinction of WMV and SMV as separate taxonomic units.     

Durable virus resistance in plants through conventional approaches: a challenge

Breeding for virus resistance is often considered the most efficient and simplest way to avoid the losses due to plant virus diseases. Resistance mechanisms are very diverse and interact with various stages of the virus cycle in the host plant. Resistances may also differ in their specificity, stability and durability. Breeding for resistance is a long and costly process, therefore to be cost effective it should provide durable protection. Three pathosystems are discussed to illustrate some of the field and laboratory approaches that can be used to assess resistance durability: Cucumber mosaic virus-specific resistance in melon, Zucchini yellow mosaic virus tolerance in zucchini squash, and extreme resistance to Potato virus X in potato. The possibility of predicting resistance durability is discussed in relation to the nature of the resistance, the genetic changes required for a virus to overcome the resistance and the effects of such changes on virus fitness.     

<Emphasis Type="Italic">Algerian watermelon mosaic virus</Emphasis> (AWMV): a new potyvirus species in the PRSV cluster

A potyvirus was isolated from a naturally infected squash plant in Algeria in 1986. Biological and serological data have revealed that the virus, initially described as H4, is related to other cucurbit-infecting potyviruses, particularly Moroccan watermelon mosaic virus (MWMV) and Papaya ringspot virus (PRSV). To establish unequivocally the taxonomic status of H4, its full-length genome sequence was established. H4 shared identities of 70% and 65% at the amino acid level with MWMV and PRSV, respectively, indicating that H4 is a distinct species of the PRSV cluster. The name Algerian watermelon mosaic virus (AWMV) is proposed for this new potyvirus species.