We have cloned cDNAs of the tobacco homolog of the luminal binding protein (BiP) that has been described in other higher eukaryotes. In contrast to the mammalian and yeast protein, tobacco BiP is encoded by a multigene family. The gene products of all the cloned members of this family contain a carboxy-terminal His-Asp-Glu-Leu peptide that may form the signal for retention in the endoplasmic reticulum. Analysis of expression patterns revealed that BiP transcripts are predominantly present in tissues with high rates of cell divisions, in secretory tissues, and in cells treated with tunicamycin. We also show that a chimeric gene containing the coding region of one of the tobacco BiP genes is able to complement a mutation in the Saccharomyces cerevisiae BiP gene.

The most abundant isoform of the 2S albumin present in seeds of Arabidopsis thaliana has been sequenced and the corresponding gene isolated. Examination of the protein and DNA sequences allows the determination of the exact proteolytic cleavage sites during posttranslational processing. Like other 2S albumins, that of Arabidopsis is made as a prepropeptide. After removal of the signal peptide, the propeptide is cleaved at four other points, giving two subunits linked by a disulfide bridge(s). Comparison of these cleavage sites with those of 2S albumins of Brassica napus and Bertholletia excelsa suggests that while individual cleavage sites between species are conserved, the four processing sites within a species are not similar, suggesting that up to four different proteases may be involved in processing 2S albumins. The Arabidopsis

The multigene family encoding the small subunit polypeptides of ribulose-1,5-bisphosphate carboxylase/oxygenase in the crucifer Arabidopsis thaliana has been isolated and the organization and structure of the individual members determined. The family consists of four genes which have been divided into two subfamilies on the basis of linkage and DNA and amino acid sequence similarities. Three of the genes, designated ats1B, ats2B, and ats3B, reside in tandem on an 8 kb stretch of the chromosome. These genes share greater than 95% similarity in DNA sequence and encode polypeptides identical in length and 96.7% similar in amino acid sequence. The fourth gene, ats1A, is at least 10 kb removed from, or completely unlinked to the B subfamily. The B subfamily genes are more similar to each other than to ats1A in nucleotide and amino acid sequence. All four genes are interupted by two introns whose placement within the coding region of the genes is conserved. The introns of the B subfamily genes are similar in length and nucleotide sequence, but show no similarity to the introns of ats1A. Comparison of the DNA sequences within the immediate 5' and 3' flanking sequences among the genes revealed only limited regions of homology. S1 analysis shows that all four genes are expressed.

A plasmid-encoded crystal protein gene (bt2) has been cloned from Bacillus thuringiensis berliner 1715. In Escherichia coli, it directs the synthesis of the 130-kDa protein (Bt2) which is toxic to larvae of Pieris brassicae and Manduca sexta. Comparison of the deduced amino acid sequence of this Bt2 protein with the B. thuringiensis kurstaki HD1 Dipel, B. thuringiensis kurstaki HD73 and B. thuringiensis sotto crystal protein sequences suggests that homologous recombination between the different genes has occurred during evolution.Treatment of the Bt2 protein with trypsin or chymotrypsin yields a 60-kDa protease-resistant and fully toxic polypeptide. The minimal portion of the Bt2 protein required for toxicity has been determined by analysing the polypeptides produced by deletion derivatives of the bt2 gene. It coincides with the 60-kDa protease-resistant Bt2 fragment and it starts between amino acids 29 and 35 at the N-terminus and terminates between positions 599 and 607 at the C-terminus.

S-Adenosylmethionine serves as a methyl group donor in numerous transmethylation reactions and plays a role in the biosynthesis of polyamines and ethylene. We have cloned and sequenced an S-adenosylmethionine synthetase gene (sam-1) of Arabidopsis thaliana. The deduced polypeptide sequence of the enzyme has extensive homology with the corresponding enzymes of Escherichia coli and yeast. Genomic hybridization indicates the presence of two adenosylmethionine synthetase genes per haploid Arabidopsis genome. RNA gel blot analysis shows that adenosylmethionine synthetase mRNA levels are high in stems and roots, correlating well with the higher enzyme activity in stems, compared with leaves. Histochemical analysis of transgenic Arabidopsis plants transformed with a chimeric beta-glucuronidase gene, under the control of 748-base pair 5' sequences of the sam-1 gene, demonstrates that the gene is expressed primarily in vascular tissues. In addition, high expression was observed in sclerenchyma and in the root cortex. A hypothesis for the strong cellular preference in the expression of the sam-1 gene is presented.