Biosynthesis of lipooligosaccharide nodulation factors: Rhizobium NodA protein is involved in N-acylation of the chitooligosaccharide backbone.

Rhizobium meliloti interacts symbiotically with alfalfa by forming root nodules in which the bacteria fix nitrogen. The Rhizobium nodulation genes nodABC are involved in the synthesis of lipooligosaccharide symbiotic signal molecules, which are mono-N-acylated chitooligosaccharides. These bacterial signals elicit nodule organogenesis in roots of legumes.

In vitro uptake and processing of maize auxin-binding proteins by ER-derived microsomes.

We have analyzed auxin-binding proteins from maize encoded by the Zm-ERabp gene family. Open reading frames of cDNA clones predict proteins containing N-terminal hydrophobic signal sequences. In vitro studies show that the Zm-ERabp1 protein can be translocated into ER-derived microsomes where it is processed and glycosylated.

Agrobacterium T-strand production in vitro: sequence-specific cleavage and 5' protection of single-stranded DNA templates by purified VirD2 protein.

Virulence proteins VirD1 and VirD2 are subunits of a relaxosome-like protein complex that mediates conjugational transfer of a Ti plasmid segment, the T-DNA, from Agrobacterium into higher plants. The VirD1-VirD2 complex binds to 25-bp repeats at the borders of the T-DNA and catalyzes sequence-specific nicking of the conjugative DNA strand (the T-strand) at the third base of these repeats. Nuclear localization signals present in VirD2 target the T-strand to plant cell nuclei.

Photoaffinity labeling of Arabidopsis thaliana plasma membrane vesicles by 5-azido-[7-3H]indole-3-acetic acid: identification of a glutathione S-transferase.

We used 5-azido-[7-3H]indole-3-acetic acid (5-azido-[7-3H]IAA), a photoaffinity analogue of the plant hormone indole-3-acetic acid (IAA), to search for auxin-binding proteins in Arabidopsis thaliana membranes. We identified an auxin-binding protein with a molecular mass of 24 kDa (Atpm24) in microsomes as well as in plasma membrane vesicles. Atpm24 was solubilized by 1% Triton X-100 and partially purified.

Sequence analysis of the 3'-terminal half of RNA 1 of wheat spindle streak mosaic virus.

cDNA complementary to the 3'-terminal half of RNA 1 of wheat spindle streak mosaic virus (WSSMV) from Southern France has been cloned and sequenced. One large open reading frame (ORF) of 4410 nucleotides and a nontranslated region (NTR) of 213 nucleotides at the 3'-end excluding the poly(A)-tail were found. Because of the amino acid sequence homology to the polyprotein of barley yellow mosaic virus (BaYMV) RNA 1, the encoded polyprotein of the sequenced region of WSSMV is supposed to comprise the C-terminal part of the putative cytoplasmic inclusion (CI) protein, the nuclear inclusion a (NIa) proteinase, the (NIb) RNA-polymerase and the capsid protein.

Genes involved in the control of growth and differentiation in plants.

The mechanisms underlying totipotency, the unique ability of isolated plant cells to regenerate into plants, offer developmental biology a unique challenge. While it has been recognised for some time that phytohormones, such as auxin and cytokinin, play a role in this process by inducing a variety of growth patterns in both isolated cells, unorganised callus and intact plants, the molecular basis of their action remains unknown. The molecular and biochemical analysis of the novel interaction between tumour-inducing soil bacteria and the wounded plant has provided a valuable insight into how plants respond to phytohormones.

Phenotype and hormonal status of transgenic tobacco plants overexpressing the rolA gene of Agrobacterium rhizogenes T-DNA.

The rolA gene of the TL-DNA of Agrobacterium rhizogenes Ri-plasmid plays a major role in establishing the hairy root syndrome in transgenic plants. Transgenic tobacco plants (Nicotiana tabacum L.) expressing constitutively the rolA gene under the transcriptional control of the 35S RNA promoter show pronounced phenotypical alterations.

Release of active cytokinin by a beta-glucosidase localized to the maize root meristem.

A beta-glucoside encoded by a cloned Zea mays complementary DNA (Zm-p60.1) cleaved the biologically inactive hormone conjugates cytokinin-O-glucosides and kinetin-N3-glucoside, releasing active cytokinin. Tobacco protoplasts that transiently expressed Zm-p60.

Single-copy T-DNA insertions in Arabidopsis are the predominant form of integration in root-derived transgenics, whereas multiple insertions are found in leaf discs.

Different patterns of T-DNA integration in Arabidopsis were obtained that depended on whether a root or a leaf-disc transformation method was used. An examination of 82 individual transgenic Arabidopsis plants, derived from 15 independent Agrobacterium-mediated transformations in which different cointegrate and binary constructs were used, indicated that the transformation method had a significant influence on the type and copy number of T-DNA integration events. Southern hybridizations showed that most of the transgenic plants produced by a leaf-disc method contained multiple T-DNA insertions (89%), the majority of which were organized as right-border inverted repeat structures (58%).

Stable expression of a single-copy rolA gene in transgenic Arabidopsis thaliana plants allows an exhaustive mutagenic analysis of the transgene-associated phenotype.

Several publications have documented the instability of transgene expression in plants. Previous genetic approaches to the study of transgene-associated phenotypes in plants were limited by this phenomenon. Here we show that a transgene can be expressed in plants with sufficient stability to allow an exhaustive mutagenic analysis of the resulting phenotype.

Identification of the initiation sequence for viral-strand DNA synthesis of wheat dwarf virus.

The intergenic region of the circular single-stranded DNA genome of geminiviruses contains a sequence potentially able to fold into a stem-loop structure. This sequence has been reported to be involved in viral replication by serving as the origin for rolling-circle replication. However, in wheat dwarf virus (WDV) a deletion of 128 bp, removing this sequence, surprisingly does not prevent de novo viral DNA synthesis, but instead abrogates the processing of replicative intermediates into monomeric genomes.

Two members of the ERabp gene family are expressed differentially in reproductive organs but to similar levels in the coleoptile of maize.

A Zea mays cDNA clone, ZmERabp4, coding for a new member of the auxin-binding protein family was isolated. The primary amino acid sequence contains an N-terminal hydrophobic leader sequence, a potential glycosylation site (Asn136-Thr-Thr) and a C-terminal KDEL motif known to be responsible for retention of proteins within the lumen of the ER. The expression pattern of the ZmERabp4 gene in various organs of maize differs from the expression pattern previously observed for the ZmERabp1 gene.

Rol genes alter hormonal requirements for protoplast growth and modify the expression of an auxin responsive promoter.

Growth characteristics of tobacco protoplasts containing rolA linked to its own promoter, or the rolB, or rolC genes of Agrobacterium rhizogenes linked to the Cauliflower Mosaic Virus 35S RNA promoter were compared with those from untransformed plants. RolA protoplasts require auxin and cytokinin for callus formation. Protoplasts overexpressing rolB and C form callus in the absence of exogenously applied auxin and cytokinin, respectively.

The Rhizobium meliloti rhizopine mos locus is a mosaic structure facilitating its symbiotic regulation.

The Rhizobium meliloti L5-30 mos locus, encoding biosynthesis of the rhizopine 3-O-methyl-scyllo-inosamine, is shown to be a mosaic structure. The mos locus consists of four open reading frames (ORFs) (ORF1 and mosABC) arranged in an operon structure. Within this locus, several domains of homology with other prokaryotic symbiotic genes (nifH, fixA, fixU, and nifT) are present, suggesting that this locus may represent a hot spot for rearrangement of symbiotic genes.

On plant growth regulators and their metabolites: a changing perspective.

From seed germination to vegetative growth and flowering virtually all aspects of plant growth and development are influenced by structurally relatively simple substances, termed phytohormones. It has been argued that the wide range of responses elicited by these substances requires a mode of action that is radically different from those of animal hormones. In contrast to animal hormones, it is often very difficult to distinguish between the site of synthesis and the site of action of phytohormones.

Restoration of fertility by antisense RNA in genetically engineered male sterile tobacco plants.

Transgenic tobacco plants (Nicotiana tabacum L.) expressing the rolC gene of Agrobacterium rhizogenes under the transcriptional control of the 35S RNA promoter are male sterile. When these plants are genetically crossed with others containing the rolC gene linked in antisense orientation to the 35S RNA promoter, hybrid progeny display restoration of male fertility.

Molecular analysis of the capsid protein gene of a german isolate of barley mild mosaic virus.

Barley mild mosaic virus (BaMMV) is one of the agents causing the barley yellow mosaic disease. The sequence corresponding to the 3'end of the BaMMV RNA1 of a German isolate was sequenced and the coding sequence for the 251 amino acid containing capsid protein was determined. Comparison of this sequence to other potyviral sequences and to the corresponding sequence of two Japanese isolates of BaMMV was done.

Transgenic tobacco plants regenerated from leaf disks can be periclinal chimeras.

Amongst rolC transgenic tobacco plants regenerated from leaf disks 6.5% are periclinal chimeras, i.e.

Polychlorinated biphenyl exposure and human disease.

Polychlorinated biphenyls (PCBs) continue to be of great environmental and occupational health interest. This review summarizes the major clinical findings reported in individuals incurring the greatest PCB exposure--those persons working in the manufacture or repair of electrical capacitors or transformers. The potential target organs addressed in the studies reviewed include the liver, lungs, skin, cardiovascular system, nervous system, certain endocrine systems, the blood/immune system, and the gastrointestinal and urinary tracts.

Use of a reporter transgene to generate arabidopsis mutants in ubiquitin-dependent protein degradation.

Ubiquitin-dependent proteolysis is a major proteolytic pathway in the cytoplasm and nucleus of eukaryotic cells. We introduced a gene encoding a substrate for this pathway into the genome of Arabidopsis thaliana. The transgene codes for a hybrid protein consisting of dihydrofolate reductase (DHFR, EC 1.