Extensive expression regulation and lack of heterologous enzymatic activity of the Class II trehalose metabolism proteins from Arabidopsis thaliana.

Trehalose metabolism has profound effects on plant growth and metabolism, but the mechanisms involved are unclear. In Arabidopsis, 21 putative trehalose biosynthesis genes are classified in three subfamilies based on their similarity with yeast TPS1 (encoding a trehalose-6-phosphate synthase, TPS) or TPS2 (encoding a trehalose-6-phosphate phosphatase, TPP). Although TPS1 (Class I) and TPPA and TPPB (Class III) proteins have established TPS and TPP activity, respectively, the function of the Class II proteins (AtTPS5-AtTPS11) remains elusive.

Improved drought tolerance without undesired side effects in transgenic plants producing trehalose.

Most organisms naturally accumulating trehalose upon stress produce the sugar in a two-step process by the action of the enzymes trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP). Transgenic plants overexpressing TPS have shown enhanced drought tolerance in spite of minute accumulation of trehalose, amounts believed to be too small to provide a protective function. However, overproduction of TPS in plants has also been found combined with pleiotropic growth aberrations.

ABI4 mediates the effects of exogenous trehalose on Arabidopsis growth and starch breakdown.

The disaccharide trehalose has dramatic effects on plant metabolism, growth and development. Arabidopsis seedlings grown on trehalose-containing medium without sucrose display increased expression of the starch synthesis gene ApL3, hyper-accumulation of starch in the cotyledons and inhibition of root growth. Here we show that the ABI4 transcription factor mediates the effects of trehalose on starch metabolism and growth, independently of abscisic acid (ABA) synthesis and hexokinase (HXK1) signaling.

Trehalose-6-phosphate synthase as an intrinsic selection marker for plant transformation.

Insertion of foreign DNA into plant genomes occurs randomly and with low frequency. Hence, a selectable marker is generally required to identify transgenic plants. Until now, all selection systems have been based on the use of non-plant genes, derived from microorganisms and usually conferring antibiotic or herbicide resistance.

The Arabidopsis trehalose-6-P synthase AtTPS1 gene is a regulator of glucose, abscisic acid, and stress signaling.

In Arabidopsis (Arabidopsis thaliana), trehalose is present at almost undetectable levels, excluding its role as an osmoprotectant. Here, we report that overexpression of AtTPS1 in Arabidopsis using the 35S promoter led to a small increase in trehalose and trehalose-6-P levels. In spite of this, transgenic plants displayed a dehydration tolerance phenotype without any visible morphological alterations, except for delayed flowering.

New selection marker for plant transformation.

A number of systems to insert foreign DNA into a plant genome have been developed so far. However, only a small percentage of transgenic plants are obtained using any of these methods. Stable transgenic plants are selected by co-introduction of a selectable marker gene, which in most cases are genes that confer resistance against antibiotics or herbicides.

The abscisic acid-related SNARE homolog NtSyr1 contributes to secretion and growth: evidence from competition with its cytosolic domain.

Syntaxins and other SNARE proteins are crucial for intracellular vesicle trafficking, fusion, and secretion. Previously, we isolated the syntaxin-related protein NtSyr1 (NtSyp121) from tobacco in a screen for abscisic acid-related signaling elements, demonstrating its role in determining the abscisic acid sensitivity of K(+) and Cl(-) channels in stomatal guard cells. NtSyr1 is localized to the plasma membrane and is expressed normally throughout the plant, especially in root tissues, suggesting that it might contribute to cellular homeostasis as well as to signaling.

Tansley Review No. 108: Molecular events of vesicle trafficking and control by SNARE proteins in plants.

Eukaryotic cells share a set of secretory pathways for the flux of membrane and protein material. In 1993, ideas about the functioning of three major proteins of the neurosecretory complex were consolidated in the SNARE hypothesis, which proposed that the interaction of these proteins provides both the specificity for vesicle targeting and the molecular machinery for fusion between vesicle and target membranes. Subsequetly, the organization, molecular mechanics and control of vesicle trafficking have become topics of intense research, and the hypothesis has evolved to accommodate new discoveries from the analysis of secretion in yeast and mammals.