Cytosolic phosphofructokinases are important for sugar homeostasis in leaves of Arabidopsis thaliana

Abstract

Background and Aims ATP-dependent phosphofructokinases (PFKs) catalyse phosphorylation of the carbon-1 position of fructose-6-phosphate, to form fructose-1,6-bisphosphate. In the cytosol, this is considered a key step in channelling carbon into glycolysis. Arabidopsis thaliana has seven genes encoding PFK isoforms, two chloroplastic and five cytosolic. This study focusses on the four major cytosolic isoforms of PFK in vegetative tissues of A. thaliana. Methods We have isolated homozygous knock-out individual mutants (pfk1, pfk3, pfk6, pfk7) and two double mutants (pfk1/7 and pfk3/6) and characterized their growth and metabolic phenotypes. Key Results In contrast to single mutants and the double mutant pfk3/6 for the hypoxia-responsive isoforms, the double mutant pfk1/7 had reduced PFK activity and shows a clear visual and metabolic phenotype with reduced shoot growth, early flowering, and elevated hexose levels. This mutant also has an altered ratio of short/long aliphatic glucosinolates and an altered root-shoot distribution. Surprisingly, this mutant does not show any major changes in short-term carbon flux and in levels of hexose-phosphates. Conclusions We conclude that the two isoforms PFK1 and PFK7 are important for sugar homeostasis in leaf metabolism and apparently source/sink relations in Arabidopsis, while PFK3 and PFK6 only play a minor role under normal growth conditions.

Mild Intermittent Cold Stimulation Affects Cardiac Substance Metabolism via the Neuroendocrine Pathway in Broilers

“…Glucose transporter 1 (GLUT1) facilitates the transfer of glucose across the cell membrane of mammalian cells, even during cold stress, thereby providing essential energy for the body [15]. Hexokinase1 (HK1), the initial irreversible rate-limiting enzyme in glycolysis, catalyzes the formation of glucose-6-phosphate (G6P) and the phosphorylation of other hexoses, while phosphofructokinase (PFK), a critical regulatory enzyme in the glycolytic pathway, catalyzes the conversion of fructose-6-phosphate (F-6-P) to fructose-1,6bisphosphate (F-1,6-P) [16,17]. Lactate dehydrogenase (LDH) B, a glycolytic enzyme, has been identified as a potential marker for evaluating environmental stress, and exposure to low temperatures increases the expression of LDHB, thus promoting the conversion of pyruvate to lactic acid, thereby promoting energy metabolism [18].…”

Plant sugar metabolism, transport and signalling in challenging environments

“…For instance, the emerging role of the ERDL/ESL vacuolar sugar transporters' family members in response to drought stress would deserve further attention (Slawinski et al, 2021). Recent works also highlight an essential role in maintaining fructose homeostasis in the plant response to abiotic stress (Cai et al, 2018; Keller et al, 2021; Mukherjee et al, 2021; Perby et al, 2022; Stein & Granot, 2018; Valifard et al, 2021). However, whether fructose plays a role as a metabolic intermediate and signal molecule still needs to be addressed.…”

Deciphering acclimation strategies to combined abiotic stresses in Arabidopsis thaliana

“…Chapter 3 PFK1 and AT5G16990. PFK1 is important for sugar homeostasis in leaf metabolism and in source-sink relationships in Arabidopsis (Perby et al, 2022), while AT5G16990 participates in the responses to oxidative stresses (Mano et al, 2005). Both of the two DEGs were upregulated after 5-day D, HT and HTD treatments, suggesting that these triple-stress responsive genes might be involved in early responses to individual (D and HT) and combined stresses (HTD) in young leaves.…”