Tunicate embryos and larvae have small cell numbers and simple anatomical features in comparison with other chordates, including vertebrates. Although they branch near the base of chordate phylogenetic trees, their degree of divergence from the common chordate ancestor remains difficult to evaluate. Here we show that the tunicate Oikopleura dioica has a complement of nine Hox genes in which all central genes are lacking but a full vertebrate-like set of posterior genes is present. In contrast to all bilaterians studied so far, Hox genes are not clustered in the Oikopleura genome. Their expression occurs mostly in the tail, with some tissue preference, and a strong partition of expression domains in the nerve cord, in the notochord and in the muscle. In each tissue of the tail, the anteroposterior order of Hox gene expression evokes spatial collinearity, with several alterations. We propose a relationship between the Hox cluster breakdown, the separation of Hox expression domains, and a transition to a determinative mode of development.

1995: Recent foraminiferal distribution in Freemansundet and Early Holocene stratigraphy on Edgeeya. Svalbard. Polar Research I4(2), 215-238.The present foraminiferal distribution (live + dead) in Freemansundet between Barentsaya and Edgeeya.Svalbard, has been compared with assemblages in raised marine Holocene deposits in Guldalen on Edgeeya. Four distinct foraminiferal assemhlages were identified in Freemansundet, the Elphidium excauarrtm-Cassidulina reniforme assemblage, the Elphidium hallandense assemblage, the Cibirides lobamlus assemblage and the Elphidium incertum-Haynesina orbiculare assemblage. Four assemblage zones (Zones A-D) have been established in the glaciomarine to marine sediment sequence in Guldalen. Only two of the recent faunal types were represented here. The Elphidium excauarum-Cassidulma reniforme assemblage, which reflects a proximal glacier envlronment, was found in the lowermost Zone A (the Elphidium excauatum Zone) and in Zone C (the Elphidium excauatum-Cassidulino reniforme Zone) in the Guldalen stratigraphy; the Elphidium incerrum-Haynesina orbiculare assemblage, which reflects ameliorated shallow water conditions, was found in the uppermost Zone D in Guldalen. The marine sequence in Guldalen represents a relatively short period of time during the Early Holocene (ca 9700 to 8300 BP). The succession of the foraminiferal assemblages suggests that the deglaciation was interrupted by a cold period with glacial stagnation just after 9600 BP (Zone B. the Asrrononion gallowayi-Nonionellina lnbradorica Zone).

Nodulin genes are specifically expressed in the nitrogen-fixing root nodules. We have identified a novel type of DNA-binding protein (CPP1) interacting with the promoter of the soybean leghemoglobin gene Gmlbc3. The DNA-binding domain of CPP1 contains two similar Cys-rich domains with 9 and 10 Cys, respectively. Genes encoding similar domains have been identified in Arabidopsis thaliana, Caenorhabditis elegans, the mouse, and human. The domains also have some homology to a Cys-rich region present in some polycomb proteins. The cpp1 gene is induced late in nodule development and the expression is confined to the distal part of the central infected tissue of the nodule. A constitutively expressed cpp1 gene reduces the expression of a Gmlbc3 promoter-gusA reporter construct in Vicia hirsuta roots. These data therefore suggest that CPP1 might be involved in the regulation of the leghemoglobin genes in the symbiotic root nodule.

Simian immunodeficiency viruses (SIV) harbor primer binding sites (PBS) matching tRNA 3Lys or tRNA 5 Lys . To study determinants of primer usage in SIV, a SIVmac239-based vector was impaired by mutating the PBS to a sequence (PBS-X2) with no match to any tRNA. By cotransfection of a synthetic gene encoding a tRNA Pro -like RNA with a match to PBS-X2, the activity of this vector could be restored to a transduction efficiency slightly lower than that of the wild-type vector. A vector with a PBS matching tRNA Pro was functional at a level slightly below that of the wild-type vector, but higher transduction efficiency could be obtained by cotransfection of a gene for an engineered tRNA Pro -tRNA 3 Lys hybrid with a match to PBS-Pro. The importance of tRNA backbone identity was further analyzed by complementing the PBS-X2 vector with a gene for a matching x2 primer with a tRNA 3 Lys backbone, which led to three-to fourfold-higher titers than those observed for the x2 primer with the tRNA Pro backbone. In summary, our results demonstrate flexibility in PBS and primer usage for SIVmac239, with PBS-primer complementarity being the major determinant, in analogy with previous findings for murine leukemia viruses and human immunodeficiency virus type 1.Retroviruses replicate through reverse transcription of the viral RNA genome into a double-stranded DNA form that is integrated into the genome of the host. The virus-encoded reverse transcriptase (RT) enzyme mediates this process through the use of a host-encoded tRNA. The 3Ј-terminal 18-nucleotide (nt) segment of the tRNA primer molecule anneals to the RNA genome at a complementary sequence known as the primer binding site (PBS). In order to synthesize a double-stranded DNA copy, two template shifts are involved. In plus-strand synthesis, the 3Ј 18-nt segment of the tRNA primer is reverse transcribed into a DNA copy, which mediates the second template shift by annealing to the minus-strand

The pea genes PsENOD12A and PsENOD12B are expressed in the root hairs shortly after infection with the nitrogen-fixing bacterium Rhizobium leguminosarum bv. viciae or after application of purified Nod factors. A 199 bp promoter fragment of the PsENOD12B gene contains sufficient information for Nod factor-induced tissue-specific expression. We have isolated a Vicia sativa cDNA encoding a 1641 amino acid protein, ENBP1, that interacts with the 199 bp ENOD12 promoter. Two different DNA-binding domains were identified in ENBP1. A domain containing six AT-hooks interacts specifically with an AT-rich sequence located between positions -95 and -77 in the PsENOD12B promoter. A second domain in ENBP1 is a cysteine-rich region that binds to the ENOD12 promoter in a sequence non-specific but metal-dependent way. ENBP1 is expressed in the same cell types as ENOD12. However, additional expression is observed in the nodule parenchyma and meristem. The presence of three small overlapping ORFs in the 5'-untranslated region of the ENBP1 cDNA indicates that ENBP1 expression might be regulated at the translational level. The interaction of ENBP1 with a conserved AT-rich element within the ENOD12 promoter and the presence of the ENBP1 transcript in cells expressing ENOD12 strongly suggest that ENBP1 is a transcription factor involved in the regulation of ENOD12. Finally, the C-terminal region of ENBP1 shows strong homology to a protein from rat that is specifically expressed in testis tissue.