Iteravirus-like genome organization of a densovirus from Sibine fusca Stoll.

The complete genome of Sibine fusca densovirus was cloned and sequenced. The genome contained 5,012 nucleotides (nt), including inverted terminal repeats (ITRs) of 230 nt with terminal hairpins of 161 nt. Its DNA sequence and monosense organization with 3 open reading frames (ORFs) is typical of the genus Iteravirus in the subfamily Densovirinae of the Parvoviridae.

Organization of the ambisense genome of the Helicoverpa armigera Densovirus.

A natural densovirus (DNV) of a serious phytophagous pest, Helicoverpa armigera, was isolated. The genome of HaDNV contained 6,039 nucleotides (nt) and included inverted terminal repeats (ITRs) of 545 nt with terminal Y-shaped hairpins of 126 nt. Its DNA sequence and ambisense organization with four typical open reading frames (ORFs) demonstrated that it belonged to the genus Densovirus in the subfamily Densovirinae of the family Parvoviridae.

Both host-plant phylogeny and chemistry have shaped the African seed-beetle radiation.

For the last 40 years, many authors have attempted to characterize the main patterns of plant-insect evolutionary interactions and understand their causes. In the present work on African seed-beetles (Coleoptera: Bruchidae), we have performed a 10-year field work to sample seeds of more than 300 species of potential host-plants (from the family Fabaceae), to obtain bruchids by rearing. This seed sampling in the field was followed by the monitoring of adult emergences which gave us the opportunity to identify host-plant use accurately. Then, by using molecular phylogenetics (on a combined data set of four genes), we have investigated the relationships between host-plant preferences and insect phylogeny. Our objectives were to investigate the level of taxonomic conservatism in host-plant fidelity and host-plant chemistry. Our results indicate that phylogenetically related insects are associated with phylogenetically related host-plants but the phylogeny of the latter cannot alone explain the observed patterns. Major host shifts from Papilionoideae to Mimosoideae subfamilies have happened twice independently suggesting that feeding specialization on a given host-plant group is not always a dead end in seed-beetles. If host-plant taxonomy and chemistry in legumes generally provide consistent data, it appears that the nature of the seed secondary compounds may be the major factor driving the diversification of a large clade specializing on the subfamily Mimosoideae in which host-plant taxonomy is not consistent with chemical similarity.

NS-3 protein of the Junonia coenia densovirus is essential for viral DNA replication in an Ld 652 cell line and Spodoptera littoralis larvae.

The genome of Junonia coenia densovirus (JcDNV) shares with members of the genus Densovirus the property of possessing structural (VP) and nonstructural (NS) genes in opposite orientations. The three NS genes located in the 5' half on one strand encode three NS proteins assumed to be involved in viral DNA replication: NS-1 and NS-2, which are common to all DNVs, and a 28-kDa polypeptide, NS-3, with a unique sequence. Whereas the essential role played by JcDNV NS-1 in viral DNA replication has been clearly established (C. Ding, M. Urabe, M. Bergoin, and R. M. Kotin, J. Virol. 76:338-345, 2002), nothing is known of the biological function(s) of NS-3. To investigate this function, we designed constructs derived from pBRJ, a plasmid encompassing an infectious sequence of JcDNV DNA (M. Jourdan, F. X. Jousset, M. Gervais, S. Skory, M. Bergoin, and B. Dumas, Virology 179:403-409, 1990), with partial or complete deletion of NS-3 sequence or with the ATG initiation codon mutated by site-directed mutagenesis. Transfection of these constructs to sensitive Ld 652 cells or Spodoptera littoralis larvae prevented the accomplishment of a productive cycle. We clearly established that the blocking of the replicative cycle in the absence of NS-3 expression occurred at the level of viral DNA replication. Replication of viral DNA could be restored by cotransfecting Ld 652 cells with a plasmid expressing JcDNV-NS-3 protein in trans. Time course analysis showed that NS-3 is produced early (6 h posttransfection) in the replicative cycle, and its production parallels that of replicative-form viral DNA. Finally, we present evidence that NS-1 and NS-2 proteins are synthesized at apparently the same levels whether or not NS-3 is expressed.