Routes of pyruvate synthesis in phosphorus‐deficient lupin roots and nodules

Abstract

Summary• Here, nodulated lupins ( Lupinus angustifolius (cv Wonga)) were hydroponically grown at low phosphate (LP) or adequate phosphate (HP).• Routes of pyruvate synthesis were assessed in phosphorus (P)-starved roots and nodules, because P-starvation can enhance metabolism of phospho enol pyruvate (PEP) via the nonadenylate-requiring PEP carboxylase (PEPc) route. Since nodules and roots may not experience the same degree of P stress, it was postulated that decreases in metabolic inorganic phosphorus (P i ) of either organ, should favour more pyruvate being synthesized from PEPc-derived malate.• Compared with HP roots, the LP roots had a 50% decline in P i concentrations and 55% higher ADP : ATP ratios. However, LP nodules maintained constant P i levels and unchanged ADP : ATP ratios, relative to HP nodules. The LP roots had greater PEP metabolism via PEPc and synthesized more pyruvate from PEPc-derived malate. In nodules, P supply did not influence PEPc activities or levels of malate-derived pyruvate.• These results indicate that nodules were more efficient than roots in maintaining optimal metabolic P i and adenylate levels during LP supply. This caused an increase in PEPc-derived pyruvate synthesis in LP roots, but not in LP nodules.

Variable P supply affects N metabolism in a legume tree, Virgilia divaricata, from nutrient-poor Mediterranean-type ecosystems

“…Furthermore the decline in plant P concentration and Pi during P deficiency concurs with previous studies in legumes, also grown under P-deficient conditions (Hernandez et al 2007;Le Roux et al 2006). However, the observation at the whole plant level may not reflect the organ-specific responses of roots and nodules to P deficiency.…”

Legume nodules from nutrient-poor soils exhibit high plasticity of cellular phosphorus recycling and conservation during variable phosphorus supply

“…alternative glycolytic reactions can bypass Pi-or ATP-requiring steps of glycolysis under Pi starvation (Theodorou and Plaxton 1996). While ATP and ADP-levels often decline under P deficiency as observed in this study and others (Duff et al 1989, Le Roux et al 2006) pyrophosphate (PPi) concentrations appear to be elevated during Pi stress (Duff et al 1989), thereby suggesting that PPi can act as an energy donor and aid in conserving limited ATP. An alternate glycolytic pathway catalysed by PPi-dependent phosphofructokinase (PFP) under P deficiency has been documented, in which PPidependant PFP bypasses the ATP-dependent phosphofructokinase (PFK), generating fructose 1,6-biphosphate (Theodorou and Plaxton 1996;Plaxton and Carswell 1999).…”

“…A reduction in nodule nucleotide-P levels has been reported in response to Pdeprivation in Glycine max (Duff et al 1989) and Lupinus angustifolius (Le Roux et al 2006). According to Theodorou and Plaxton (1993), these reductions in Pi and adenylate pools, which accompany Pi-starvation are functionally important.…”

“…The decreased nodule biomass, in of the spite higher below ground investment in relative root biomass during P stress, appears to be a typical response to Pdeficiency in legumes (Vadez et al 1997, Le Roux et al 2006). This may be attributed to the lower P utilisation efficiency for biomass production, which was evident in the P deficient and P resupply nodules.…”

“…In addition, many of the legume studies examining the effect of P deficiency on BNF focuses on model legumes (Tang et al 2001, Le Roux et al 2006, Schulze et al 2006Sulieman et al 2013, Thuynsma et al 2014. The P poor soils of the Cape Floristic Region (CFR) in South Africa has a high legume diversity (Goldblatt and Manning 2002), yet not much is known about the functional adaptations they elicit with nutrient fluctuations.…”