Control of glucose influx into glycolysis and pleiotropic effects studied in different isogenic sets of Saccharomyces cerevisiae mutants in trehalose biosynthesis

Abstract

The GGS1/TPS1 gene of the yeast Saccharomyces cerevisiae encodes the trehalose-6-phosphate synthase subunit of the trehalose synthase complex. Mutants defective in GGS1/TPS1 have been isolated repeatedly and they showed variable pleiotropic phenotypes, in particular with respect to trehalose content, ability to grow on fermentable sugars, glucose-induced signaling and sporulation capacity. We have introduced the fdp1, cif1, byp1 and glc6 alleles and the ggs1/tps1 deletion into three different wild-type strains, M5, SP1 and W303-1A. This set of strains will aid further studies on the molecular basis of the complex pleiotropic phenotypes of ggs1/tps1 mutants. The phenotypes conferred by specific alleles were clearly dependent on the genetic background and also differed for some of the alleles. Our results show that the lethality caused by single gene deletion in one genetic background can become undetectable in another background. The sporulation defect of ggs1/tps1 diploids was neither due to a deficiency in G1 arrest, nor to the inability to accumulate trehalose. Ggs1/tps1 delta mutants were very sensitive to glucose and fructose, even in the presence of a 100-fold higher galactose concentration. Fifty-percent inhibition occurred at concentrations similar to the Km values of glucose and fructose transport. The inhibitory effect of glucose in the presence of a large excess of galactose argues against an overactive glycolytic flux as the cause of the growth defect. Deletion of genes of the glucose carrier family shifted the 50% growth inhibition to higher sugar concentrations. This finding allows for a novel approach to estimate the relevance of the many putative glucose carrier genes in S. cerevisiae. We also show that the GGS1/TPS1 gene product is not only required for the transition from respirative to fermentative metabolism but continuously during logarithmic growth on glucose, in spite of the absence of trehalose under such conditions.

Trehalose 6-phosphate is indispensable for carbohydrate utilization and growth in Arabidopsis thaliana

“…Results therefore point to glycolysis as a site of T6P regulation in Arabidopsis. This finding would be analogous to more comprehensive studies carried out in yeast (36,38). In contrast to mammalian hexokinases, both yeast and plant hexokinases are not subject to physiologically relevant feedback regulation by G6P (39,40).…”

Trehalose 6-phosphate regulates starch synthesis via posttranslational redox activation of ADP-glucose pyrophosphorylase

“…Recent studies show that the precursor of trehalose, T6P, is an indispensable regulator of sugar utilization in eukaryotic organisms as different as yeasts and plants (18,20,22). However, apart from regulating glycolysis by inhibiting hexokinase in some yeast species, other sites of T6P action have until now not been known (20,(25)(26)(27). No target of T6P has been found in plants, where hexokinases are insensitive to T6P (19).…”

The trehalose pathway and intracellular glucose phosphates as modulators of potassium transport and general cation homeostasis in yeast

“…As TPS1 is a key regulator of glucose metabolism (Neves et al, 1995), we further investigated whether this phenotype was glucose-dependent, finding that the same tolerance could be acquired in galactose medium ( Figure 1B). The tolerance to toxic cations conferred by overexpression of TPS1 was also observed in liquid cultures growing in exponential phase (data not shown).…”