Downregulation of pyrophosphate: d-fructose-6-phosphate 1-phosphotransferase activity in sugarcane culms enhances sucrose accumulation due to elevated hexose-phosphate levels

Analyses of transgenic sugarcane clones with 45–95% reduced cytosolic pyrophosphate: d-fructose-6-phosphate 1-phosphotransferase (PFP, EC 2.7.1.90) activity displayed no visual phenotypical change, but significant changes were evident in in vivo metabolite levels and fluxes during internode development. In three independent transgenic lines, sucrose concentrations increased between three- and sixfold in immature internodes, compared to the levels in the wildtype control. There was an eightfold increase in the hexose-phosphate:triose-phosphate ratio in immature internodes, a significant restriction in the triose phosphate to hexose phosphate cycle and significant increase in sucrose cycling as monitored by 13C nuclear magnetic resonance. This suggests that an increase in the hexose-phosphate concentrations resulting from a restriction in the conversion of hexose phosphates to triose phosphates drive sucrose synthesis in the young internodes. These effects became less pronounced as the tissue matured. Decreased expression of PFP also resulted in an increase of the ATP/ADP and UTP/UDP ratios, and an increase of the total uridine nucleotide and, at a later stage, the total adenine nucleotide pool, revealing strong interactions between PPi metabolism and general energy metabolism. Finally, decreased PFP leads to a reduction of PPi levels in older internodes indicating that in these developmental stages PFP acts in the gluconeogenic direction. The lowered PPi levels might also contribute to the absence of increases in sucrose contents in the more mature tissues of transgenic sugarcane with reduced PFP activity

Novel IgG-degrading enzymes of the IgdE protease family link substrate specificity to host tropism of <i>Streptococcus</i> species

Recently we have discovered an IgG degrading enzyme of the endemic pig pathogen S. suis designated IgdE that is highly specific for porcine IgG. This protease is the founding member of a novel cysteine protease family assigned C113 in the MEROPS peptidase database. Bioinformatical analyses revealed putative members of the IgdE protease family in eight other Streptococcus species. The genes of the putative IgdE family proteases of S. agalactiae, S. porcinus, S. pseudoporcinus and S. equi subsp. zooepidemicus were cloned for production of recombinant protein into expression vectors. Recombinant proteins of all four IgdE family proteases were proteolytically active against IgG of the respective Streptococcus species hosts, but not against IgG from other tested species or other classes of immunoglobulins, thereby linking the substrate specificity to the known host tropism. The novel IgdE family proteases of S. agalactiae, S. pseudoporcinus and S. equi showed IgG subtype specificity, i.e. IgdE from S. agalactiae and S. pseudoporcinus cleaved human IgG1, while IgdE from S. equi was subtype specific for equine IgG7. Porcine IgG subtype specificities of the IgdE family proteases of S. porcinus and S. pseudoporcinus remain to be determined. Cleavage of porcine IgG by IgdE of S. pseudoporcinus is suggested to be an evolutionary remaining activity reflecting ancestry of the human pathogen to the porcine pathogen S. porcinus. The IgG subtype specificity of bacterial proteases indicates the special importance of these IgG subtypes in counteracting infection or colonization and opportunistic streptococci neutralize such antibodies through expression of IgdE family proteases as putative immune evasion factors. We suggest that IgdE family proteases might be valid vaccine targets against streptococci of both human and veterinary medical concerns and could also be of therapeutic as well as biotechnological use

Tissue disks as an experimental system for metabolic flux analysis in the sugarcane culm.

AgriwetenskappeInstituut vir PlantbiotegnologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Carbon allocation to the insoluble fraction, respiration and triose-phosphate cycling in the sugarcane culm

AgriwetenskappeInstituut vir PlantbiotegnologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Stable isotope ratios and aroma profile changes induced due to innovative wine dealcoholisation approaches

The high ethanol level in wine has become an important issue for all the main wine producing countries. Several techniques are available to the wine industry to reduce the ethanol content; among them, the membrane contactors are certainly one of the newest. Very few studies on the effect of this practice on the wine quality and aroma profile and on the stable isotopes composition are available. A pilot and industrial plant equipped with the membrane contactor system were used in the study in the dealcoholisation on several white and red wines. Significant changes for several classes of aroma compounds in both pilot- and industrial-scale experiments were observed, even though these changes were not always in perfect agreement with the sensory evaluation carried out. Finally, modifications on the δ18O of up to 1‰ for 2 %v/v and of up to 4‰ for 8 %v/v ethanol removal were encountered. An increase of δ13C of ethanol of up to 1.1‰ for 2 % and of up to 2.3‰ for 4 % of dealcoholisation rate was also observed. Dealcoholisation via membrane contactor seemed to affect the overall wine composition (aroma and flavour), even though the main concern resided on the alteration of the isotopic composition which could be linked to product authenticity issues