A set of mapping markers have been designed for Arabidopsis thaliana that correspond to DNA fragments amplified by the polymerase chain reaction (PCR). The ecotype of origin of these amplified fragments can be determined by cleavage with a restriction endonuclease. Specifically, 18 sets of PCR primers were synthesized, each of which amplifies a single mapped DNA sequence from the Columbia and Landsberg erecta ecotypes. Also identified was at least one restriction endonuclease for each of these PCR products that generates ecotype-specific digestion patterns. Using these co-dominant cleaved amplified polymorphic sequences (CAPS), an Arabidopsis gene can be unambiguously mapped to one of the 10 Arabidopsis chromosome arms in a single cross using a limited number of F2 progeny.

Transposable genetic elements are a ed to be a feature of all eukayotic genomes. Their ntification, however, has largely been haphazard, limited principally to organisms subjected to molecular or genetic scrutiny. We assessed the phylogenetic distribution of copw-flke retrotransposons, a class of t able element that proliferates by reverse transcription, using a polymerase chain reaction asay designed to detect copia-like element reverse transcriptase sequences. copia-ilke retrotranpsons were Idetified in 64 plant species as well as the photosynthetic protist Volxcarter.

Canis familiaris allergen 1 (Can f 1) and Canis familiaris allergen 2 (Can f 2) are the two major allergens present in dog dander extracts. We now report the isolation of cDNAs encoding both proteins and present their nucleotide and deduced amino acid sequences. Can f 1, produced by tongue epithelial tissue, has homology with the von Ebner’s gland (VEG) protein, a salivary protein not previously thought to have allergenic properties. Can f 2, produced by tongue and parotid gland, has homology with mouse urinary protein (MUP), a known allergen. Both VEG protein and MUP are members of the lipocalin family of small ligand‐binding proteins. Recombinant forms of Can f 1 and Can f 2 were produced and tested for immunoglobulin E (IgE) reactivity. Among dog‐allergic subjects, 45% had IgE directed exclusively to rCan f 1, and 25% had IgE to both rCan f 1 and rCan f 2. In addition, both recombinant proteins were able to cross‐link IgE and elicit histamine release from peripheral blood leucocytes in vitro. These findings confirm that Can f 1 and Can f 2 are major and minor dog allergens, respectively, and demonstrate that recombinant forms of dog allergens retain at least some IgE‐binding epitopes.

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We describe a superfamily of Arabidopsis thaliana retrotransposable elements that consists of at least ten related families designated Ta1-Ta10. The Ta1 family has been described previously. Two genomic clones representing the Ta2 and Ta3 elements were isolated from an A. thaliana (race Landsberg erecta) lambda library using sequences derived from the reverse transcriptase region of Ta1 as hybridization probes. Nucleotide sequence analysis showed that the Ta1, Ta2 and Ta3 families share greater than 75% amino acid identity in pairwise comparisons of their reverse transcriptase and RNase H genes. In addition to Ta1, Ta2 and Ta3, we identified seven other related retrotransposon families in Landsberg erecta, Ta4-Ta10, using degenerate primers and the polymerase chain reaction to amplify a highly conserved region of retrotransposon-encoded reverse transcriptase. One to two copies of elements Ta2-Ta10 are present in the genomes of the A. thaliana races Landsberg erecta and Columbia indicating that the superfamily comprises at least 0.1% of the A. thaliana genome. The nucleotide sequences of the reverse transcriptase regions of the ten element families place them in the category of copia-like retrotransposons and phylogenetic analysis of the amino acid sequences suggests that horizontal transfer may have played a role in their evolution.

Substantial evidence is provided to corroborate our previous finding that Escherichiu coli ribosomes recognize two binding sites on the 5' end of alfalfa mosaic virus (AMV) RNA 4 [for a preliminary report see Castel, A., Kraal, B., Kerklaan, P. R. M., Klok, J., and Bosch, L. (1977) Proc. Nut1 Acud. Sci. U.S.A. 74, 5509-55131. Translation can start at either site using AcPhetRNA or Met-tRNA as initiator and takes place in the same reading frame along the monocistronic mRNA. The size and composition of the isolated extra NHz-terminal fragment of the acetylphenylalanyl product were found to be in agreement with the 5' non-coding region of the messenger. Removal of the 5'-terminal cap structure of AMV RNA 4 did not influence significantly both initiation reactions. Ribosomal protein S1 was essential for binding as well as incorporation of both met-tRNA and AcPhe-tRNA. A similar interaction on the ribosome was found for AcPhe-tRNA directed by AMV RNA 4 as for Met-tRNA directed by either AMV RNA 4 or MS2 RNA with respect to the influence of initiation factors. It is concluded that the heterologous plant viral messenger is reliably translated in the E. coli system and that E. coli ribosomes recognize with high specificity an extra initiation site close to the 5' extremity of the messenger. The relationship of this site to a hypothetical entry site involved in the early recognition in the initiation mechanism between ribosome and messenger is discussed.Investigations dealing with cloning of eukaryotic DNA in Escherichiu coli have demonstrated that the eukaryotic sequence can be transcribed correctly, provided that the foreign DNA is inserted properly. More difficulties are met at the level of translation and the fundamental question has been raised whether the prokaryotic protein-synthesizing machinery is able to express eukaryotic information. A number of reports have appeared which seem to answer this question to the affirmative. After cloning of eukaryotic genes like those of somatostatin [l], rat proinsulin [2], chicken ovalbumin [3,4] and mouse dihydrofolate reductase [S] production of the corresponding proteins by the bacteria could indeed be detected. In most cases the eukaryotic structural gene was fused to E. coli transcriptional and translational control reAbbreviations. AMV, alfalfa mosaic virus; IF-1, IF-2 and IF-3, initiation factors 1, 2 and 3, tRNAF', methionine-accepting tRNA which can not be formylated.Enzyme. Phosphomonoesterase orthophosphoric-monoester phosphohydrolase (EC 3.1.3.1).gions, in such a way that the leader sequence of the eukaryotic message, preceding the initiating ATG codon, was eliminated. In the case of the mouse dihydrofolate reductase this leader sequence was replaced by poly(dG). It is generally assumed [6,7] that the leader on the messenger contains specific signals which have to be recognized by the ribosome in order to initiate polypeptide synthesis in the correct reading frame. It remains to be seen, therefore, whether prokaryotic ribosomes are able to recognize such eukary...

Poly(A)+ RNA isolated from root nodules of yellow lupin (Lupinus luteus, var. Ventus) has been used as a template for the construction of a cDNA library. The ds cDNA was synthesized and inserted into the Hind III site of plasmid pBR 322 using synthetic Hind III linkers. Clones containing sequences specific for nodules were selected by differential colony hybridization using 32P-labeled cDNA synthesized either from nodule poly(A)+ RNA or from poly(A)+ RNA of uninfected root as probes. Among the recombinant plasmids, the cDNA gene for leghemoglobin was identified. The protein structure derived from its nucleotide sequence was consistent with known amino acid sequence of lupin Lb II. The cloned lupin Lb cDNA hybridized to poly(A)+ RNA from nodules only, which is in accordance with the general concept, that leghemoglobin is expressed exclusively in nodules.