Thioredoxins in<Emphasis Type="Italic">Arabidopsis</Emphasis> and other plants

Regulation of disulfide dithiol exchange has become increasingly important in our knowledge of plant life. Initially discovered as regulators of light-dependent malate biosynthesis in the chloroplast, plant thioredoxins are now implicated in a large panel of reactions related to metabolism, defense and development. In this review we describe the numerous thioredoxin types encoded by the Arabidopsis genome, and provide evidence that they are present in all higher plants. Some results suggest cross-talk between thioredoxins and glutaredoxins, the second family of disulfide dithiol reductase. The development of proteomics in plants revealed an unexpectedly large number of putative target proteins for thioredoxins and glutaredoxins. Nevertheless, we are far from a clear understanding of the actual function of each thioredoxin in planta. Although hampered by functional redundancies between genes, genetic approaches are probably unavoidable to define which thioredoxin interacts with which target protein and evaluate the physiological consequences.     

Sugar-induced adventitious roots in<Emphasis Type="Italic"> Arabidopsis</Emphasis> seedlings

The effects of sugars on root growth and on development of adventitious roots were analyzed in Arabidopsis thaliana. Seeds were sown on agar plates containing 0.0–5.0% sugars and placed vertically in darkness (DD) or under long day (LD, 16 h:8 h) conditions, so that the seedlings were constantly attached to the agar medium. In the sucrose-supplemented medium, seedlings showed sustained growth in both DD and LD. However, only dark-grown seedlings developed adventitious roots from the elongated hypocotyl. The adventitious roots began to develop 5 days after imbibition and increased in number until day 11. They could, however, be initiated at any position along the hypocotyl, near the cotyledon or the primary root. They were initiated in the pericycle in the same manner as ordinary lateral roots. Sucrose, glucose and fructose greatly stimulated the induction of adventitious roots, but mannose or sorbitol did not. Sucrose at concentrations of 0.5–2.0% was most effective in inducing adventitious roots, although 5.0% sucrose suppressed induction. Direct contact of the hypocotyl with the sugar-supplemented agar medium was indispensable for the induction of adventitious roots. Electronic Publication     

Mutation in<Emphasis Type="Italic"> slowmo</Emphasis> causes defects in<Emphasis Type="Italic"> Drosophila</Emphasis> larval locomotor behaviour

We have identified a mutant slowmotion phenotype in first instar larval peristaltic behaviour of Drosophila. By the end of embryogenesis and during early first instar phases, slowmo mutant animals show a marked decrease in locomotory behaviour, resulting from both a reduction in number and rate of peristaltic contractions. Inhibition of neurotransmitter release, using targeted expression of tetanus toxin light chain (TeTxLC), in the slowmo neurons marked by an enhancer-trap results in a similar phenotype of largely absent or uncoordinated contractions. Cloning of the slowmo gene identifies a product related to a family of proteins of unknown function. We show that Slowmo is associated with mitochondria, indicative of it being a mitochondrial protein, and that during embryogenesis and early larval development is restricted to the nervous system in a subset of cells. The enhancer-trap marks a cellular component of the CNS that is seemingly required to regulate peristaltic movement.