Characterization of citrus sinensis pyrophosphate- dependent phosphofructokinase gene family and its responses to cold stress

VAZQUEZ, D.E.; BELLO, F.; MARGARIT, E.; PODESTÁ, F.E.

Capital Federal

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS

CHARACTERIZATION OF CITRUS SINENSIS PYROPHOSPHATE-DEPENDENT PHOSPHOFRUCTOKINASEGENE FAMILY AND ITS RESPONSES TO COLD STRESSEzequiel Margarit (1), Fernando Bello (2), Daniel Vazquez(2), Florencio Podestá (1)(1) CEFOBI-CONICET. (2) EEA INTA Concordia.Abstract: Phosphofructokinase catalyzes the glycolytic conversionof fructose-6-phosphate to fructose-1,6-bisphosphate, a central stepin sugar metabolism. In plants, two forms of the enzyme are known:PFK (EC 2.7.1.11), which is ATP-dependent, and PFP (EC 2.7.1.90),which is pyrophosphate-dependent. Most PFPs are heterotetramerscomposed of two subunits of 66 (PFPa) or 60 kDa (PFPb), encodedby a varying number of genes. PFP contributes to glycolysis in anumber of conditions that lead to a drop in nucleotide levels, suchas anoxia, Pi deprivation, and cold stress. Previous work from ourgroup evidenced higher PFP protein levels after frost events in C.sinensis juice sacs, thus indicating a role in the enhancement ofglycolysis in these tissues.To gain further insight, we searched C. sinensis genome for putativePFP subunits and bioinformatically characterized their sequencesand structures. Sequences were compared to those known forother species both by alignment and phylogentically. Expressionlevels of PFPs were studied in vegetative and reproductive tissuesof C. sinensis var. Valencia Late obtained from field-grown plants.To further characterize PFP responses to cold in vegetative tissues,PFP gene expression was studied in frost-exposed leaves, and alsoin leaves from cold-treated plantlets.We report the identification of four sequences coding for threecatalytic and one regulatory subunit in the C. sinensis genome. Expressionstudies showed that PFPa and PFPb1 were expressed atdifferent levels in all tissues assayed and, notably, with different a/bsubunit ratios. PFPb2 was almost exclusively detected in flowers,while PFPb3 was found in mature leaves, roots, and fruit tissues.Cold treatments changed the expression pattern of these proteins.This work provides cues to understand the role of PFP during normalconditions and through the energetic rescue of the cell understressful conditions in citrus.Keywords: citrus, metabolism, phosphofructokinases, cold, stress.