Jean-Alexandre Barré: Babinski's brilliant student.

Guillain-Barré Syndrome, (GBS), is a popular eponym that comes from a paper written in 1916 by Doctors. Guillain, Barré, and Strohl. Its spectrum has been enlarged considerably since the first description of it. Jean Alexandre Barré was a French neurologist, whose name is still widely associated with that of Georges Guillain, (1876-1961). He is also known for the leg manoeuvre. As Joseph Babinski's brilliant student, (1857-1932), we wanted to briefly retrace his biography in order to highlight some of the salient points within it and subjects that are topical for young neurologists today.

The rib1 mutant is resistant to indole-3-butyric acid, an endogenous auxin in Arabidopsis.

The presence of indole-3-butyric acid (IBA) as an endogenous auxin in Arabidopsis has been recently demonstrated. However, the in vivo role of IBA remains to be elucidated. We present the characterization of a semi-dominant mutant that is affected in its response to IBA, but shows a wild-type response to indole-3-acetic acid (IAA), the predominant and most studied form of auxin. We have named this mutant rib1 for resistant to IBA. Root elongation assays show that rib1 is specifically resistant to IBA, to the synthetic auxin 2,4-dichlorophenoxyacetic acid, and to auxin transport inhibitors. rib1 does not display increased resistance to IAA, to the synthetic auxin naphthalene acetic acid, or to other classes of plant hormones. rib1 individuals also have other root specific phenotypes including a shortened primary root, an increased number of lateral roots, and a more variable response than wild type to a change in gravitational vector. Adult rib1 plants are morphologically indistinguishable from wild-type plants. These phenotypes suggest that rib1 alters IBA activity in the root, thereby affecting root development and response to environmental stimuli. We propose models in which RIB1 has a function in either IBA transport or response. Our experiments also suggest that IBA does not use the same mechanism to exit cells as does IAA and we propose a model for IBA transport.

Expression of tryptophan decarboxylase and tyrosine decarboxylase genes in tobacco results in altered biochemical and physiological phenotypes.

The substrate specificity of tryptophan (Trp) decarboxylase (TDC) for Trp and tyrosine (Tyr) decarboxylase (TYDC) for Tyr was used to modify the in vivo pools of these amino acids in transgenic tobacco. Expression of TDC and TYDC was shown to deplete the levels of Trp and Tyr, respectively, during seedling development. The creation of artificial metabolic sinks for Trp and Tyr also drastically affected the levels of phenylalanine, as well as those of the non-aromatic amino acids methionine, valine, and leucine. Transgenic seedlings also displayed a root-curling phenotype that directly correlated with the depletion of the Trp pool. Non-transformed control seedlings could be induced to display this phenotype after treatment with inhibitors of auxin translocation such as 2,3,5-triiodobenzoic acid or N-1-naphthylphthalamic acid. The depletion of aromatic amino acids was also correlated with increases in the activities of the shikimate and phenylpropanoid pathways in older, light-treated transgenic seedlings expressing TDC, TYDC, or both. These results provide in vivo confirmation that aromatic amino acids exert regulatory feedback control over carbon flux through the shikimate pathway, as well as affecting pathways outside of aromatic amino acid biosynthesis.

Uncoupled defense gene expression and antimicrobial alkaloid accumulation in elicited opium poppy cell cultures.

Treatment of opium poppy (Papaver somniferum L.) cell cultures with autoclaved mycelial homogenates of Botrytis sp. resulted in the accumulation of sanguinarine. Elicitor treatment also caused a rapid and transient induction in the activity of tyrosine/dopa decarboxylase (TYDC, EC 4.1.1.25), which catalyzes the conversion of L-tyrosine and L-dopa to tyramine and dopamine, respectively, the first steps in sanguinarine biosynthesis. TYDC genes were differentially expressed in response to elicitor treatment. TYDC1-like mRNA levels were induced rapidly but declined to near baseline levels within 5 h. In contrast, TYDC2-like transcript levels increased more slowly but were sustained for an extended period. Induction of TYDC mRNAs preceded that of phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) mRNAs. An elicitor preparation from Pythium aphanidermatum was less effective in the induction of TYDC mRNA levels and alkaloid accumulation; however, both elicitors equally induced accumulation of PAL transcripts. In contrast, treatment with methyl jasmonate resulted in an induction of TYDC but not PAL mRNAs. The calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and the protein kinase inhibitor staurosporine partially blocked the fungal elicitor-induced accumulation of sanguinarine. However, only staurosporine and okadaic acid, an inhibitor of protein phosphatases 1 and 2A, blocked the induction of TYDC1-like transcript levels, but they did not block the induction of TYDC2-like or PAL transcript levels. These data suggest that activation mechanisms for PAL, TYDC, and some later sanguinarine biosynthetic enzymes are uncoupled.