A reduction in age-enhanced gluconeogenesis extends lifespan.

The regulation of energy metabolism, such as calorie restriction (CR), is a major determinant of cellular longevity. Although augmented gluconeogenesis is known to occur in aged yeast cells, the role of enhanced gluconeogenesis in aged cells remains undefined. Here, we show that age-enhanced gluconeogenesis is suppressed by the deletion of the tdh2 gene, which encodes glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a protein that is involved in both glycolysis and gluconeogenesis in yeast cells. The deletion of TDH2 restores the chronological lifespan of cells with deletions of both the HST3 and HST4 genes, which encode yeast sirtuins, and represses the activation of gluconeogenesis. Furthermore, the tdh2 gene deletion can extend the replicative lifespan in a CR pathway-dependent manner. These findings demonstrate that the repression of enhanced gluconeogenesis effectively extends the cellular lifespan.

Plastidial glyceraldehyde-3-phosphate dehydrogenase deficiency leads to altered root development and affects the sugar and amino acid balance in Arabidopsis.

Glycolysis is a central metabolic pathway that, in plants, occurs in both the cytosol and the plastids. The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate with concomitant reduction of NAD(+) to NADH. Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described. However, the in vivo functions of the plastidial isoforms remain unresolved. In this work, we have identified two Arabidopsis (Arabidopsis thaliana) chloroplast/plastid-localized GAPDH isoforms (GAPCp1 and GAPCp2). gapcp double mutants display a drastic phenotype of arrested root development, dwarfism, and sterility. In spite of their low gene expression level as compared with other GAPDHs, GAPCp down-regulation leads to altered gene expression and to drastic changes in the sugar and amino acid balance of the plant. We demonstrate that GAPCps are important for the synthesis of serine in roots. Serine supplementation to the growth medium rescues root developmental arrest and restores normal levels of carbohydrates and sugar biosynthetic activities in gapcp double mutants. We provide evidence that the phosphorylated pathway of Ser biosynthesis plays an important role in supplying serine to roots. Overall, these studies provide insights into the in vivo functions of the GAPCps in plants. Our results emphasize the importance of the plastidial glycolytic pathway, and specifically of GAPCps, in plant primary metabolism.

Caged substrates applied to high content screening: an introduction with an eye to the future.

The use of photoremovable protecting groups in biology affords the end user high temporal, spatial, and concentration control of reagents and substrates. High content screening and other large-scale biology applications would benefit greatly from these advantages. Herein, we report progress in this field by highlighting the recent development of controllable siRNA (csiRNA), which is a dormant siRNA that can be activated using 365 nm light. Two different experimental designs are described to highlight the temporal and concentration variables that can be controlled. First, the RNAi process is activated at two timepoints, 24- and 48-h post-transfection, to demonstrate that the action of csiRNA does not begin until activated. Second, increasing light dosage exposure to cells transfected with csiRNA that controls the concentration of active siRNA molecules. All experiments are conducted in a 96-well format with light delivered through the UCOM device.