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J H Weil

Publications and source records attributed to J H Weil.

At least 19 recordsLinked to original sources
PubMed2002

Role of editing in plant mitochondrial transfer RNAs.

Editing in plant mitochondria consists in C to U changes and mainly affects messenger RNAs, thus providing the correct genetic information for the biosynthesis of mitochondrial (mt) proteins. But editing can also affect some of the plant mt tRNAs encoded by the mt genome. In dicots, a C to U editing event corrects a C:A mismatch into a U:A base pair in the acceptor stem of mt tRNA(Phe) (GAA). In larch mitochondria, three C to U editing events restore U:A base pairs in the acceptor stem, D stem and anticodon stem, respectively, of mt tRNA(His) (GUG). For both these mt RNA(Phe) and tRNA(His), editing of the precursors is a prerequisite for their processing into mature tRNAs. In potato mt tRNA(Cys) (GCA), editing converts a C28:U42 mismatch in the anticodon stem into a U28:U42 non-canonical base pair, and reverse transcriptase minisequencing has shown that the mature mt tRNA(Cys) is fully edited. In the bryophyte Marchantia polymorpha this U residue is encoded in the mt genome and evolutionary studies suggest that restoration of a U28 residue is necessary when it is not encoded in the gene. However, in vitro studies have shown that neither processing of the precursor, nor aminoacylation of tRNA(Cys), requires C to U editing at this position. But sequencing of the purified mt tRNA(Cys) has shown that Psi is present at position 28, indicating that C to U editing is a prerequisite for the subsequent isomerization of U into Psi at position 28.

Cytidine↗
PubMed2001

Editing of plant mitochondrial transfer RNAs.

Editing in plant mitochondria consists in C to U changes and mainly affects messenger RNAs, thus providing the correct genetic information for the biosynthesis of mitochondrial (mt) proteins. But editing can also affect some of the plant mt tRNAs encoded by the mt genome. In dicots, a C to U editing event corrects a C:A mismatch into a U:A base-pair in the acceptor stem of mt tRNAPhe (GAA). In larch mitochondria, three C to U editing events restore U:A base-pairs in the acceptor stem, D stem and anticodon stem, respectively, of mt tRNAHis (GUG). For both these mt tRNAs editing of the precursors is a prerequisite for their processing into mature tRNAs. In potato mt tRNACys (GCA), editing converts a C28:U42 mismatch in the anticodon stem into a U28:U42 non-canonical base-pair, and reverse transcriptase minisequencing has shown that the mature mt tRNACys is fully edited. In the bryophyte Marchantia polymorpha this U residue is encoded in the mt genome and evolutionary studies suggest that restoration of the U28 residue is necessary when it is not encoded in the gene. However, in vitro studies have shown that neither processing of the precursor nor aminoacylation of tRNACys requires C to U editing at this position. But sequencing of the purified mt tRNACys has shown that psi is present at position 28, indicating that C to U editing is a prerequisite for the subsequent isomerization of U into psi at position 28.

Mitochondria↗
PubMed1996

Editing and import: strategies for providing plant mitochondria with a complete set of functional transfer RNAs.

The recombinations and mutations that plant mitochondrial DNA has undergone during evolution have led to the inactivation or complete loss of a number of the 'native' transfer RNA genes deriving from the genome of the ancestral endosymbiont. Following sequence divergence in their genes, some native mitochondrial tRNAs are 'rescued' by editing, a post-transcriptional process which changes the RNA primary sequence. According to in vitro studies with the native mitochondrial tRNA(Phe) from potato and tRNA(His) from larch, editing is required for efficient processing. Some of the native tRNA genes which have been inactivated or lost have been replaced by tRNA genes present in plastid DNA sequences acquired by the mitochondrial genome during evolution, which raises the problem of the transcriptional regulation of tRNA genes in plant mitochondria. Finally, tRNAs for which no gene is present in the mitochondrial genome are imported from the cytosol. This process is highly specific for certain tRNAs, and it has been suggested that the cognate aminoacyl-tRNA synthetases may be responsible for this specificity. Indeed, a mutation which blocks recognition of the cytosolic Arabidopsis thaliana tRNA(Ala) by the corresponding alanyl-tRNA synthetase also prevents mitochondrial import of this tRNA in transgenic plants. Conversely, no significant mitochondrial co-import of the normally cytosol-specific tRNA(Asp) was detected in transgenic plants expressing the yeast cytosolic aspartyl-tRNA synthetase fused to a mitochondrial targeting sequence, suggesting that, although necessary, recognition by a cognate aminoacyl-tRNA synthetase might not be sufficient to allow tRNA import into plant mitochondria.

Biological Transport↗
PubMed1995

Alterations in chlorophyll a/b binding proteins in Solanaceae cybrids.

In this study we have constructed a number of plants (cybrids), in which the nuclear genome of Nicotiana plumbaginifolia is combined with the plastome of Atropa belladonna, or the nuclear genome of N. tabacum with plastomes of Lycium barbarum, Scopolia carniolica, Physochlaine officinalis or Nolana paradoxa. Our biochemical and immunological analyses prove that in these cybrids the biogenesis of the chlorophyll a/b binding proteins (CAB) of the light harvesting complex II (LHCII) is altered. Besides normal sized CAB polypeptides of 27, 25.5 and 25 kDa, which become less abundant, the cybrids analyzed have additional polypeptides of 26, 24.5 and 24 kDa. Direct protein micro-sequencing showed that at least two truncated 26 kDa CAB polypeptides in plant cells containing a nucleus of N. plumbaginifolia and plastids of A. belladonna are encoded by the type 1 Lhcb genes. These polypeptides are 11-12 amino acids shorter at the N-terminus than the expected size. Based on the available data we conclude that the biogenesis of the LHCII in vivo may depend on plastome-encoded factor(s). These results suggest that plastome-encoded factors that cause specific protein degradation and/or abnormal processing might determine compartmental genetic incompatibility in plants.

Amino Acid Sequence↗
PubMed1993

Editing corrects mispairing in the acceptor stem of bean and potato mitochondrial phenylalanine transfer RNAs.

Editing is a general event in plant mitochondrial messenger RNAs, but has never been detected in a plant mitochondrial transfer RNA (tRNA). We demonstrate here the occurrence of a tRNA editing event in higher plant mitochondria: in both bean and potato, the C encoded at position 4 in the mitochondrial tRNA(Phe)(GAA) gene is converted into a U in the mature tRNA. This nucleotide change corrects the mismatched C4-A69 base-pair which appears when folding the gene sequence into the cloverleaf structure and it is consistent with the fact that C to U transitions constitute the common editing events affecting plant mitochondrial messenger RNAs. The tRNA(Phe)(GAA) gene is located upstream of the single copy tRNA(Pro)(UGG) gene in both the potato and the bean mitochondrial DNAs. The sequences of potato and bean tRNA(Pro)(UGG) genes are colinear with the sequence of the mature bean mitochondrial tRNA(Pro)(UGG), demonstrating that this tRNA is not edited. A single copy tRNA(Ser)(GCU) gene was found upstream of the tRNA(Phe) gene in the potato mitochondrial DNA. A U6-U67 mismatched base-pair appears in the cloverleaf folding of this gene and is maintained in the mature potato mitochondrial tRNA(Ser)(GCU), which argues in favour of the hypothesis that the editing system of plant mitochondria can only perform C to U or occasionally U to C changes.

Base Sequence↗
PubMed1992

The Euglena gracilis rbcS gene contains introns with unusual borders.

We have recently shown that, in Euglena gracilis, leader sequences are transferred by trans-splicing to the vast majority of cytoplasmic mRNAs. Trans-splicing is involved in the maturation of the rbcS transcript, which encodes eight small subunits of the ribulose 1,5 bisphosphate carboxylase/oxygenase. In this report, we show that the Euglena rbcS gene introns are different from introns found in plant rbcS genes. In addition these introns do not have the conserved 5' and 3' border sequences found in introns of eucaryotic nuclear-encoded pre-mRNAs, and they do not present any homology with self-splicing introns of groups I and II. Secondary structure analyses show that the 5' and 3' ends of Euglena introns can base-pair, suggesting that an unusual splicing mechanism exists in Euglena.

Amino Acid Sequence↗
PubMed1992

In Euglena, spliced-leader RNA (SL-RNA) and 5S rRNA genes are tandemly repeated.

In Euglena gracilis, a 26 nucleotide leader sequence (spliced leader sequence = SL) is transferred by trans-splicing to the 5' end of a vast majority of cytoplasmic mRNAs (8). The SL originates from the 5' extremity of a family of closely related snRNAs (SL-RNAs) which are about 100 nucleotide long. In this paper we present the nucleotide sequences of two SL-RNA genes, confirming the sequences previously established by sequencing purified SL-RNAs. Although some SL-RNA genes are dispersed throughout the genome, we show that the majority of SL-RNA genes are located on 0.6 kb repeated units which also encode the cytoplasmic 5S rRNA. We estimate that the copy number of these repeated units is about 300 per haploid genome. The association of SL-RNA and 5S rRNA genes in tandemly repeated units is also found in nematodes but paradoxically does not exist in trypanosomes which are phylogenically much closer to Euglena. We also show that a high number of sequences analogous to the 26 nucleotide SL are dispersed throughout the genome and are not associated with SL-RNAs.

Animals↗
PubMed1992

In vivo import of a normal or mutagenized heterologous transfer RNA into the mitochondria of transgenic plants: towards novel ways of influencing mitochondrial gene expression?

Evidence that nuclear-encoded RNAs are present inside mitochondria has been reported from a wide variety of organisms, and is presumed to be due to import of specific cytosolic RNAs. In plants, the first examples were the mitochondrial leucine transfer RNAs of bean. In all cases, the evidence is circumstantial, based on hybridization of the mitochondrial RNAs to nuclear and not mitochondrial DNA. Here we show that transgenic potato plants carrying a leucine tRNA gene from bean nuclear DNA contain RNA transcribed from the introduced gene both in the cytosol and inside mitochondria, providing proof that the mitochondrial leucine tRNA is derived from a nuclear gene and imported into the mitochondria. The same bean gene carrying a 4 bp insertion in the anticodon loop was also expressed in transgenic potato plants and the transcript found to be present inside mitochondria, suggesting that this natural RNA import system could eventually be used to introduce foreign RNA sequences into mitochondria.

Base Sequence↗
PubMed1992

The psbL gene from bell pepper (Capsicum annuum): plastid RNA editing also occurs in non-photosynthetic chromoplasts.

We have determined the nucleotide sequence of the plastid psbL gene from bell pepper. This gene has an ACG as a first codon. Isolation of RNA from pepper leaves and ripe fruits and subsequent sequencing of the psbL cDNA revealed that this ACG codon is post-transcriptionally edited into an AUG initiation codon in both leaves and fruits. These data indicate that the RNA editing machinery which exists in chloroplasts is still functional in chromoplasts from ripe fruits.

Amino Acid Sequence↗
PubMed1992

Identification of a cDNA for the plastid-located geranylgeranyl pyrophosphate synthase from Capsicum annuum: correlative increase in enzyme activity and transcript level during fruit ripening.

Geranylgeranyl pyrophosphate synthase is a key enzyme in plant terpenoid biosynthesis. Using specific antibodies, a cDNA encoding geranylgeranyl pyrophosphate synthase has been isolated from bell pepper (Capsicum annuum) ripening fruit. The cloned cDNA codes for a high molecular weight precursor of 369 amino acids which contains a transit peptide of approximately 60 amino acids. In-situ immunolocalization experiments have demonstrated that geranylgeranyl pyrophosphate synthase is located exclusively in the plastids. Expression of the cloned cDNA in E. coli has unambiguously demonstrated that the encoded polypeptide catalyzes the synthesis of geranylgeranyl pyrophosphate by the addition of isopentenyl pyrophosphate to an allylic pyrophosphate. Peptide sequence comparisons revealed significant similarity between the sequences of the C. annuum geranylgeranyl pyrophosphate synthase and those deduced from carotenoid biosynthesis (crtE) genes from photosynthetic and non-photosynthetic bacteria. In addition, four highly conserved regions, which are found in various prenyltransferases, were identified. Furthermore, evidence is provided suggesting that conserved and exposed carboxylates are directly involved in the catalytic mechanism. Finally, the expression of the geranylgeranyl pyrophosphate synthase gene is demonstrated to be strongly induced during the chloroplast to chromoplast transition which occurs in ripening fruits, and is correlated with an increase in enzyme activity.

Amino Acid Sequence↗
PubMed1992

Spiroplasma citri UGG and UGA tryptophan codons: sequence of the two tryptophanyl-tRNAs and organization of the corresponding genes.

From the total tRNAs of Spiroplasma citri, we isolated and purified two tRNA(Trp) species by using chromatography on an RPC-5 column followed by denaturing polyacrylamide gel electrophoresis. The sequence of the two tRNAs, as well as the sequences of the corresponding genes, were determined. One of the two tRNA(Trp) species has a CCA anticodon and is able to pair with the universal UGG tryptophan codon, while the second has a U*CA (U* is a modified uridine) anticodon and is able to pair with UGA but also with UGG in accordance with the "U:N wobble" rule. Thus, in S. citri, UGA is not a stop codon but codes for tryptophan. The two tRNA(Trp) genes, together with a third tRNA gene, tRNA(Ser) (CGA), belong to a single transcription unit. The nucleotide sequences of the two tRNA(Trp) species show 82.9% similarity. The two spiroplasmal tRNA(Trp) species can be aminoacylated by using an aminoacyl-tRNA synthetase fraction from S. citri. In contrast, the enzyme fraction from Escherichia coli aminoacylates tRNA(Trp) (CCA) but not tRNA(Trp) (U*CA).

Base Sequence↗
PubMed1991

Short leader sequences may be transferred from small RNAs to pre-mature mRNAs by trans-splicing in Euglena.

Very closely related short sequences are present at the 5' end of cytoplasmic mRNAs in Euglena as evidenced by comparison of cDNA sequences and hybrid-arrested translation experiments. By cloning Euglena gracilis nuclear DNA and isolating the rbcS gene (encoding the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase), we have shown that the short leader sequence does not flank the nuclear gene sequence. The leader sequences were found to constitute the 5' extremities of a family of small RNAs. Sequencing six members of this family revealed a striking similarity to vertebrate U snRNAs. We propose that a trans-splicing mechanism transfers the spliced leader (SL) sequence from these small RNAs (SL RNAs) to pre-mature mRNAs. Transfer of leader sequences to mRNAs by trans-splicing has been shown only in trypanosomes where cis-splicing is unknown, and in nematodes where not more than 10% of the mRNAs have leader sequences. Our results strongly suggest that Euglena is a unique organism in which both a widespread trans-splicing and a cis-splicing mechanism co-exist.

Animals↗
PubMed1991

Anther-specific, developmentally regulated expression of genes encoding a new class of proline-rich proteins in sunflower.

We have used RNA gel blot analysis to demonstrate the anther-specific expression of three genes in sunflower. Expression of these genes was first detected shortly before flower opening, which occurs sequentially on the sunflower inflorescence, and continues during pollination. In contrast, these genes are not expressed (or only weakly expressed) in a male-sterile line in which anther development aborts. In situ hybridization experiments showed that these genes are only expressed in the single cell layer of the sunflower anther epidermis. In the case of one of these genes, which codes for an abundant mRNA, we report the peptide sequences deduced from the sequence of two similar but non identical cDNAs. These proteins contain a potential signal peptide and are characterized by the presence of a proline-rich region which reads KPSTPAPPPPPP(PP)K. Our results also suggest that several proline-rich proteins of unknown functions are specifically synthesized during the maturation of anthers in sunflower.

Amino Acid Sequence↗
PubMed1991

Post-transcriptional regulation by light of the biosynthesis of Euglena ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit.

In Euglena gracilis, the amounts of the mature small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) increase during cell greening, while an analysis of the transcripts, performed at different stages of chloroplast development, shows no difference in the amounts of the corresponding mRNA. Pulse-chase experiments followed by immunoprecipitation show a significant increase in the rate of synthesis of the large molecular weight precursor (which consists of a transit peptide followed by eight small subunits) beginning after 12 h of illumination. Nevertheless, its half life does not change significantly during the chloroplast development. The results presented strongly suggest that the regulation of the expression of the Rubisco small subunit occurs at the translational level.

Animals↗
PubMed1991

Structure and expression of sunflower ubiquitin genes.

Two ubiquitin genes, designated UbB1 and UbB2, were isolated from a sunflower genomic library. They encode polyubiquitin transcripts corresponding to six repeats of the monomer. Northern blot analysis identified several different transcript size classes: both UbB1 and UbB2 transcripts are found in the most abundant 1.6 kb class. In contrast to the previously isolated UbF transcript which is present at high levels in flowers, UbB1 and UbB2 are expressed constitutively at low levels in different tissues. The levels of the two transcripts increase after heat stress. The two genes exhibit strong homology suggesting that they may result from duplication and conversion. Surprisingly, UbB1 gene shows structural similarities with the chicken ubiquitin heat shock gene, in particular the presence of an intron located just in front of the first ATG.

Amino Acid Sequence↗
PubMed1991

Subcellular location and expression level of a chimeric protein consisting of the maize waxy transit peptide and the beta-glucuronidase of Escherichia coli in transgenic potato plants.

The transit peptide of the maize waxy protein (a nuclear-encoded amyloplast protein of the maize endosperm) was studied with respect to its role in subcellular protein targeting in transgenic potato plants. TP30, a chimeric precursor protein consisting of the waxy transit peptide and an additional 34 amino acids of the mature waxy protein fused to the beta-glucuronidase of Escherichia coli, was expressed in potato plants under the control of the 35S promoter of cauliflower mosaic virus. This fusion protein is imported not only into amyloplasts, the natural target organelles in the maize plant, but also into chloroplasts. In contrast, Gus, the beta-glucuronidase alone, which was also expressed in parallel experiments in transgenic potato plants is always found in the cytosol of the plant cells. As a consequence of the different subcellular locations of TP30 and Gus, we observed differences in the expression rates of the respective proteins in leaf cells, resulting in higher steady state levels of TP30 compared to Gus. In tuber cells, no correlation between intracellular location and expression of the proteins was found.

Biological Transport↗