Jacques Henry Weil

Nucleotide sequence of the split tRNA UAA Leu gene from Vicia faba chloroplasts: evidence for structural homologies of the chloroplast tRNALeu intron with the intron from the autosplicable Tetrahymena ribosomal RNA precursor

SummaryThe gene encoding the tRNAUAALeufrom broad bean chloroplasts has been located on a 5.1 kbp long BamHI fragment by analysis of the DNA sequence of an XbaI subfragment. This gene is 536 bp long and is split in the anticodon region. The 451 bp long intron shows high sequence homology over about 100 bp from each end with the corresponding regions of the maize chloroplast tRNAUAALeuintron. These conserved sequences are probably involved in the splicing reaction, for they can be folded into a secondary structure which is very similar to the postulated structure of the intron from the autosplicable ribosomal RNA precursor of Tetrahymena. Very little sequence conservation is found in the 5′-and 3′-flanking regions of the broad bean and maize chloroplast tRNAUAALeugenes.

Genes for tRNAGly, tRNAHis, tRNALys, tRNAPhe, tRNASer and tRNATyr are encoded in Oenothera mitochondrial DNA

SummaryThe genes coding for tRNAGly, tRNAHis, tRNALys, tRNAPhe, tRNASer and tRNATyr have been identified in Oenothera mitochondrial DNA. Sequence analysis of these genes and their surrounding sequences are presented and compared with other known tRNA genes from plant mitochondria. All six deduced tRNA sequences can be folded into the classical cloverleaf structure model. Only the tRNAHis gene shows high homology with the corresponding chloroplast gene and thus appears to be derived from a transfer event of chloroplast sequences into the mitochondrial genome. The sequences surrounding this gene, however, show little similarity with the chloroplast genome. The other five deduced tRNAs display a much lower similarity with their chloroplast counterparts and thus appear to be genuine mitochondrial tRNAs. These tRNAs are highly conserved between monocots and dicots with maximally three nucleotides differing between the Oenothera sequences and their wheat homologues. A purine-rich sequence is found upstream of each tRNA gene in Oenothera, similar to wheat mitochondrial tRNA genes, that could be involved in transcription signalling.

Transfer RNA genes ofZea mays chloroplast DNA

A minimum of 37 genes corresponding to tRNAs for 17 different amino acids have been localized on the restriction endonuclease cleavage site map of theZea mays chloroplast DNA molecule. Of these, 14 genes corresponding to tRNAs for 11 amino acids are located in the larger of the two single-copy regions which separate the two inverted copies of the repeat region. One tRNA gene is in the smaller single-copy region. Each copy of the large repeated sequence contains, in addition to the ribosomal RNA genes, 11 tRNA genes corresponding to tRNAs for 8 amino acids. The genes for tRNA2Ile and tRNAAla map in the ribosomal spacer sequence separating the 16S and 23S ribosomal RNA genes. The three isoaccepting species for the tRNAsLeu and the three for tRNAsSer, as well as the two isoaccepting species for tRNAAsn, tRNAGly, tRNAsIle, tRNAsMet, tRNAsThr, are shown to be encoded at different loci.Two independent methods have been used for the localization of tRNA genes on the physical map of the maize chloroplast DNA molecule: (a) cloned chloroplast DNA fragments were hybridized with radioactively-labelled total 4S RNAs, the hybridized RNAs were then eluted, and identified by two-dimensional polyacrylamide gel electrophoresis, and (b) individual tRNAs were32P-labelledin vitro and hybridized to DNA fragments generated by digestion of maize chloroplast DNA with various restriction endonucleases.

Nucleotide sequence of the psbB gene of Euglena gracilis

The psbB gene codes for the «51 kDa» chlorophyll a apoprotein of photosystem II. In Euglena gracilis, the psbB gene has been shown to be located on restriction fragment Eco H (5.5 kbp) of chloroplast DNA [1]. We present here the nucleotide sequence of the Euglena psbB gene

Dr. Leon S. Dure, III (1931–2014)

with a bachelor’s degree in philosophy, and then served as a Marine Corps officer in the mountains of Korea. After returning home and leaving formal duty in the Marines (because of Leon’s loyalty and love for the Marine Corps as well as his patriotism, he remained an active reserve Officer, reaching the rank of Colonel before retiring from the Marine Reserves), Leon returned to the University of Virginia where he received an M. S. degree in plant embryology. He then continued his graduate education at the University of Texas where he received his Ph.D. in plant physiology. After this, Leon joined the developing faculty of biochemistry of the UGA in 1960 as a postdoctoral researcher working on bioluminescence—a pioneering step as he was in fact the first postdoctoral researcher at the UGA! He continued on the faculty of biochemistry and retired in 2003 as Franklin Professor of Biochemistry after a distinguished research career. Leon was also greatly respected as a masterful teacher, which the Franklin professorship validated as one of the best. In the mid-1960s, Dr. Dure developed his independent research laboratory where he focused on the molecular bases of seed germination. During this early period, one of the important findings was discovery and characterization of long-lived messenger or mRNA that coded for specialized proteins in germinating cotton seed. This was one of the earliest reports on the long-term stability of at least some eukaryotic mRNAs. Leon’s group did one of the most thorough and excellent studies at the time on PolyA + and Poly A– mRNAs in a plant system. Dr. Dure’s research continued to focus on many aspects of cotton seed embryogenesis and germination, including additional work on the seed mRNAs and studies on cotton seed storage proteins from general characterization of their complexity and abundance to biosynthetic pathways. The role of abscisic acid in these processes represents another major group of contributions. Dr. Leon S. Dure III passed away on May 11, 2014. He was Franklin Professor of Biochemistry at the time of his retirement from the University of Georgia (UGA), Athens, Georgia, where he spent his entire faculty career from 1960 to 2003. Born in January 1931 in Macon, Georgia, Leon grew up at his family home in East Belmont Farm, Kenswick, Virginia. He graduated from the University of Virginia

Carotenoid Biosynthesis and Regulation in Plants

Great impetus to the investigation of carotenoid biosynthesis was given by the introduction of Porter and Lincoln (1950) of the hypothesis that coloured carotenoids were formed by the sequential dehydrogenation of the unsaturated polyenes detected in several tomato fruit lines. Since then the implications of these studies have led to a massive exploration which now allows to describe the different steps of the biosynthetic pathway. Several reviews (Porter and Spurgeon, 1979; Camara and Moneger, 1982; Porter and Spurgeon, 1983; Jones and Porter, 1986; Bramley and Mackenzie, 1988; Britton, 1988) present different pictures of our advances in this field, but they also inevitably point to persistent gaps in our understanding. A search of the literature leaves the impression that as far as the enzymology and the underlying basis of its control are concerned, little progress has been made there. The lag can be accounted for by the exceptionally great difficulties that such studies must face. In this chapter, we wish to consider some of the recent development in this area, focusing mainly on higher plants.

Mapping of tRNA Genes on the Circular DNA Molecule of Spinacia oleracea Chloroplasts

Chloroplasts contain their own complement of tRNAs, which are different from those of the cytoplasm and those of the mitochondria (Weil et al. 1977). The chloroplast tRNA structure is similar to that of prokaryotic tRNAs, at least for the two chloroplast tRNAs whose nucleotide sequences have been determined (Chang et al. 1976; Guillemaut and Keith 1977), and they are coded for by chloroplast DNA (Tewari and Wildman 1970; Gruol and Haselkorn 1976; Haff and Bogorad 1976; McCrea and Hershberger 1976; Schwartzbach et al. 1976). The genes coding for chloroplast rRNAs have been mapped on higher plant and algal chloroplast DNAs. In maize and spinach, the chloroplast rRNA genes are located on two inverted repeats (Bedbrook et al. 1977; Whitfeld et al. 1978); in Euglena, the chloroplast rRNA genes exist as three clustered tandem repeats (Gray and Hallick 1978; Rawson et al. 1978). But until now, the chloroplast tRNA genes have not been localized. In this paper we describe the fractionation and identification of spinach ( Spinacia oleracea ) chloroplast tRNAs and the first results of our efforts to map the tRNA genes on spinach chloroplast DNA (a circular molecule of ~ 90 × 10 6 daltons). Unbroken Chloroplasts (Herrmann et al. 1975) were used in the preparation of tRNAs, aminoacyl-tRNA synthetases, and high-molecular-weight DNA. The tRNAs were prepared by phenol treatment of detergent-lysed chloroplasts, precipitated by ethanol, dissolved in 1 M NaCl, diluted to 0.2 M NaCl, incubated with DNase, and purified on DEAE-cellulose columns (Burkard et al. 1970). Aminoacyl-tRNA synthetases were obtained...

RNA Editing in Wheat Mitochondria: A New Mechanism for the Modulation of Gene Expression

RNA editing is a recently discovered mechanism involved in the modulation of gene expression. It is a process which results in the production of mRNAs with a nucleotide sequence differing from that of the template DNA (Simpson and Shaw, 1989). This phenomenom was initially described in the mitochondria (mt) of protozoa (Benne et al. 1986). We have recently (Gualberto et al., 1989) shown that RNA editing is also required for the correct expression of plant mt genes. Several wheat mt mRNA sequences were found to differ from the corresponding gene sequences in that a number of cytidine (C) residues are converted into uridine (U) residues. Most C to U conversions analysed cause a change of the amino acid coded by the modified codon. These modifications contribute to the conservation of mitochondrial protein sequences among higher plants. Furthermore, C to U conversions enable the plant mt translation system to use the universal genetic code, since CGG codons, which were postulated to code for tryptophan (Fox and Leaver, 1981), are changed into UGG codons where a tryptophan is to be incorporated in the protein.

Programs of the NATO Science Committee

1. Research Fe l lowsh ips in Science and Technology These fellowships are available to scientists who want to pursue their work or continue their training in another member country, for instance during a post-doctoral or a sabbatical stay. In contrast to the other programs, which are administered through international panels in Brussels, these fellowships are under the responsibility of a national administrator in each member country. This allows each country to define its priorities when granting the fellowships, but, as a consequence, the criteria, eligibility conditions, duration and amount of these fellowships may vary somewhat in each member country. This is the list of the national administrators: