Genomic exploration of the hemiascomycetous yeasts: 17. Yarrowia lipolytica.

A total of 4940 random sequence tags of the dimorphic yeast Yarrowia lipolytica, totalling 4.9 Mb, were analyzed. BLASTX comparisons revealed at least 1229 novel Y. lipolytica genes 1083 genes having homology with Saccharomyces cerevisiae genes and 146 with genes from various other genomes. This confirms the rapid sequence evolution assumed for Y. lipolytica. Functional analysis of newly discovered genes revealed that several enzymatic activities were increased compared to S. cerevisiae, in particular, transport activities, ion homeostasis, and various metabolism pathways. Most of the mitochondrial genes were identified in contigs spanning more than 47 kb. Matches to retrotransposons were observed, including a S. cerevisiae Ty3 and a LINE element. The sequences have been deposited with EMBL under the accession numbers AL409956-AL414895.

Genomic organization of the yeast Yarrowia lipolytica.

We produced electrophoretic karyotypes of the reference strain E150 and of seven other isolates from different geographical origins to study the genomic organization of the dimorphic yeast Yarrowia lipolytica. These karyotypes differed in the number and size of the chromosomal bands. The karyotype of the reference stain E150 consisted of five bands of between 2.6 and 4.9 Mb in size. This strain contained at least five rDNA clusters, from 190 to 620 kb in size, which were scattered over most of the chromosomes. The assignment of 43 markers, including rRNA genes and three centromeres, to the E150 bands defined five linkage groups. Hybridization to the karyotypes of other isolates with pools of markers of each linkage group showed that linkage groups I, II, IV and V were conserved in the strains tested whereas group III was not and was split between at least two chromosomes in most strains. Use of a meganuclease I-SceI site targeted to one locus of E150 linkage group III showed that two chromosomes actually comigrated in band III of this strain. Our results are compatible with six chromosomes defining the haploid complement of strains of Y. lipolytica and that, despite an unprecedented chromosome length polymorphism, the overall structure of the genome is conserved in different isolates.

Colocalization of centromeric and replicative functions on autonomously replicating sequences isolated from the yeast Yarrowia lipolytica.

Two sequences (ARS18 and ARS68) displaying autonomous replication activity were previously cloned in the yeast Yarrowia lipolytica. The smallest fragment (1-1.3 kb) required for extrachromosomal replication of a plasmid is significantly larger in Y. lipolytica than in Saccharomyces cerevisiae. Neither autonomously replicating sequence (ARS) is homologous with known ARS or centromere (CEN) consensus sequences. They share short regions of sequence similarity with each other. These ARS fragments also contain Y. lipolytica centromeres: (i) integration of marker genes at the ARS loci results in a CEN-linked segregation of the markers, (ii) an ARS on a plasmid largely maintains sister chromatid attachment in meiosis I, and (iii) integration of these sequences at the LEU2 locus leads to chromosome breakage. Deletions performed on ARS18 show that CEN and ARS functions can be physically separated, but both are needed to establish a replicating plasmid.

Isolation and characterization of anti-rotavirus immunoglobulins secreted by cloned hybridoma cell lines.

Five monoclonal hybridoma cell lines secreting antibodies against bovine rotavirus have been produced and four of them characterized by immunostaining of structural polypeptides electrophoretically transferred on to nitrocellulose sheets. Three hybridomas appeared to be directed against the major structural polypeptide (VP39) of the virion. These three monoclonals cross-reacted with the major polypeptide of simian rotavirus and human rotavirus. A fourth hybridoma appeared to react specifically with the high-molecular weight external polypeptide (VP89) and its cleavage products. A cross-reaction was observed with human Wa strain but not with SA11. The fifth hybridoma, even though reacting in an immunofluorescent test, did not show any reactivity by immunostaining. None of the monoclonals neutralized the infectivity of bovine rotavirus.

Infantile gastroenteritis caused by rotavirus: comparison of enzyme-linked immunosorbent assay and electron microscopy for rapid diagnosis.

ELISA and negative contrast EM have used for the detection of rotavirus in one hundred stools from children, less than two years old, hospitalized for acute gastro-enteritis during the winter 1977-78. Samples obtained from the same children some months after hospitalization were also tested. A good correlation was found between the results given by EM and ELISA, but the later technique turned out to be more sensitive (12% more positive using ELISA). A rotavirus infection could be demonstrated in 73% of the patients. In the stools of 3 children we found a second virus in association with the rotavirus, and in two cases a pathogenic bacterium. When a second serum specimen was available from children previously infected by rotavirus it was always possible to detect a significant increase in CF antibodies. Several months after hospitalization a 2nd survey indicated that the rotavirus was no longer present but calicivirus, echovirus, coxsackievirus and adenovirus could be detected in those asymptomatic children.

Reovirus-like agent (rotavirus) associated with neonatal calf gastroenteritis in France.

A reo-like virus (calf rotavirus) was shown to be associated with cases of neonatal calf diarrhea in France. The virus could be detected in more than 50 p. 100 of diarrheic fecal samples, while it was practically absent in control samples originating from healthy calves that had never had diarrhea. The results obtained by electron microscopy and immunofluorescent studies indicate that the virus is closely related or identical to the agent isolated originally in the United States.