Quantitative trait loci for resistance against Yellow rust in two wheat-derived recombinant inbred line populations.

Yellow rust, which is a major disease in areas where cool temperatures prevail, can strongly influence grain yield. To control this disease, breeders have extensively used major specific resistance genes. Unfortunately this kind of resistance is rapidly lost due to pathogen adaptation. More-durable resistance against yellow rust can be achieved using quantitative resistance derived from cultivars with well-established durable resistance. The winter wheat Camp Remy has maintained a high level of resistance for over 20 years. In order to map quantitative trait loci (QTLs) for durable yellow rust resistance, we analysed a set of 98 F(8) recombinant inbred (RI) lines derived from the cross Camp RemyxMichigan Amber. We also mapped QTLs for adult resistance to yellow rust using the International Triticae Mapping Initiative RI population (114 lines derived from the cross Opata85xsynthetic hexaploid). Two and five QTLs, respectively, were identified from these two populations. This work has highlighted the importance of the centromeric region of chromosome 2B and the telomeric regions of chromosomes 2AL and 7DS in durable yellow rust resistance. The same chromosomal regions are also implicated in resistance to other pathogens.

Wheat transformation with glutenin gene.

The rheological properties of wheat grains are associated with the composition of the starchy endosperm in high molecular weight (HMW) glutenin proteins. The HMW glutenin 1xDy12 subunit gene was co introduced with the screenable bar and the reporter gus marker genes in the commercial spring wheat Minaret cultivar (cv). The gene of interest and the marker genes were carried by two separated plasmids, the pBS10BH1 and the pAhC25 respectively. Seven days old calli initiated from immature embryos were bombarded by use of the PDS-1000/He device. A number of different bombardment and culture conditions were tested. These parameters were evaluated on the basis of GUS transient expression. Among those a 4 degrees C cold pre-treatment of the spikes before immature embryos were excised, the culture medium incorporating activated charcoal, silver nitrate and glucose yielded higher GUS transient expression rate. The selective agent bialaphos was maintained at various stages during culture from induction of somatic embryogenesis to rooting of regenerated plantlets. 137 bialaphos resistant plants were obtained among which 109 were carried to maturity. Transgenic plants were characterized by PCR, Southern and SDS-PAGE analysis of the glutenin content.

Fos and Jun oncogenes transactivate chimeric or native promoters containing AP1/GCN4 binding sites in plant cells.

The function of mammalian transcription factors of the leucine zipper class was investigated in leaf-derived protoplasts of tobacco. In transient expression experiments, Fos and Jun strongly activated chimeric promoters composed of the TATA box region of the cauliflower mosaic virus 35S transcript preceded by one to five copies of an AP1/GCN4 binding site. Fos and Jun also stimulated a wheat high molecular weight glutenin promoter in which similar binding sites are located more than 500 base pairs from its transcription start site. Both the DNA binding and the transcription activation domains of these proteins were required for proper promoter stimulation by Fos and Jun. Each factor alone was partially active, suggesting that at least the Fos protein can associate with an endogenous plant transcription factor. These observations support the hypothesis that sequences related to AP1/GCN4 binding sites could be cis-acting modules involved in the transcriptional regulation of plant genes.

Yeast RAS2 affects cell viability, mitotic division and transient gene expression in Nicotiana species.

Overexpression of the budding yeast RAS2 gene in Nicotiana plumbaginifolia cells revealed that RAS2 acted as 'suicide' gene in freshly isolated protoplasts from leaves and blocked cell proliferation in cell suspension-derived protoplasts. Among a series of genes tested (such as npt II, CDC35, PDE2), RAS2 was the only one to block the expression of the cat gene, as measured in a transient gene expression assay. Another ras gene, v-Ha-ras, had similar effects. Furthermore, the RAS2 effect was species-specific and depended on the modulation of hormonal metabolism in the transfected cells, while no differences were noticed between the normal and the activated val19 gene. Transfected plant cells are shown to synthesize a RAS2 protein of the same electrophoretic mobility as the yeast RAS2 product. The results are discussed in the broader context of the evolutionarily conserved ras genes involved in vital cellular functions.

A TY1 element is inserted in the CYR1 control region of Saccharomyces cerevisiae strain AB320.

Southern blotting using a 5'-proximal probe of the Saccharomyces cerevisiae CYR1 gene has revealed heterogeneity in laboratory strains. It is demonstrated that strain AB320 contains a Ty1 element inserted in the promoter region of CYR1. The Ty1 orientation suggests that transcription of CYR1 is initiated downstream from the insertion region.

Yeast adenylate cyclase catalytic domain is carboxy terminal.

Subcloning of DNA fragments from the gene coding for yeast adenylate cyclase has permitted, after complementation studies in S. cerevisiae cdc35 mutants as well as E. coli cya mutants, to identify the sequence coding for the catalytic domain of the protein. No homology is found between the yeast cyclase catalytic domain and the homologous domain found in E. coli adenylate cyclase. Analysis by Northern blotting of yeast polyA mRNA has shown the existence of multiple transcriptional products of the gene. A putative origin of a major transcript (3.5 kb) would allow synthesis of a ca. 100,000 dalton protein exhibiting cyclase activity in its carboxy terminal domain, and having 7 repeats of 17 amino acids at its amino terminal end. Several note-worthy features, including the possibility of transcriptional control by the general control of amino acids biosynthesis, are present at this putative origin. Data are presented suggesting that a much longer gene product might also be synthesized from the CDC35 gene. Neither the gene organization nor the amino acid sequence of the protein does display any homology with the adenylate cyclase gene and protein of Escherichia coli. This suggests a case of evolutionary convergence for the synthesis of cAMP in prokaryotes and eukaryotes.

Molecular cloning of the tsm0185 gene responsible for adenylate cyclase activity in Saccharomyces cerevisiae.

The gene of Saccharomyces cerevisiae responsible for adenylate cyclase activity was cloned by complementation of a thermosensitive tsm0185 mutation in yeast; it was also shown to complement the yeast cyr1 mutation. Preliminary results indicate the presence of a repeated sequence on the same genomic fragment.

Isolation and characterization of DNA sequences from Triticum aestivum which function as origins of replication in Saccharomyces cerevisiae.

Recombinant YIp5 plasmids with the DNA from Triticum aestivum are capable of autonomous replication in Saccharomyces cerevisiae. The URA transformants are unstable without selection pressure, and transformation of yeast cells with these plasmids occurs at high frequency. The cloned sequences were characterized and analyzed to state their belonging to Triticum tribe.