Nodule-enhanced expression of a sucrose phosphate synthase gene member (MsSPSA) has a role in carbon and nitrogen metabolism in the nodules of alfalfa (Medicago sativa L.)

Abstract

Sucrose phosphate synthase (SPS) catalyzes the first step in the synthesis of sucrose in photosynthetic tissues. We characterized the expression of three different isoforms of SPS belonging to two different SPS gene families in alfalfa (Medicago sativa L.), a previously identified SPS (MsSPSA) and two novel isoforms belonging to class B (MsSPSB and MsSPSB3). While MsSPSA showed nodule-enhanced expression, both MsSPSB genes exhibited leaf-enhanced expression. Alfalfa leaf and nodule SPS enzymes showed differences in chromatographic and electrophoretic migration and differences in Vmax and allosteric regulation. The root nodules in legume plants are a strong sink for photosynthates with its need for ATP, reducing power and carbon skeletons for dinitrogen fixation and ammonia assimilation. The expression of genes encoding SPS and other key enzymes in sucrose metabolism, sucrose phosphate phosphatase and sucrose synthase, was analyzed in the leaves and nodules of plants inoculated with Sinorhizobium meliloti. Based on the expression pattern of these genes, the properties of the SPS isoforms and the concentration of starch and soluble sugars in nodules induced by a wild type and a nitrogen fixation deficient strain, we propose that SPS has an important role in the control of carbon flux into different metabolic pathways in the symbiotic nodules.

GmEXPB2, a Cell Wall β-Expansin Gene, Affects Soybean Nodulation through Modifying Root Architecture and Promoting Nodule Formation and Development

“…host plants (Djordjevic, 2004;Aleman et al, 2010). Therefore, better root growth can facilitate nodulation and vice versa.…”

“…It has been documented that bacteria within nodules require an abundant supply of carbohydrates and related substances generated from host plants for nodule growth and N 2 fixation (Streeter, 1980;Reich et al, 2006;Aleman et al, 2010). The nodule vascular system is important for importing these compounds into nodules.…”

Improvement in nitrogen fixation capacity could be part of the domestication process in soybean

“…SPS catalyzes the formation of sucrose-6-phosphate from UDP-glucose and fructose-6-phosphate, and this enzyme has a putative role in nodule carbon partitioning to different metabolic pathways (Aleman et al, 2010).…”

Changes in the Activity of Carbon and Nitrogen Metabolising Enzymes in Nodules of Bold and Small Seeded Lentil Cultivars

“…Sucrose is the main carbohydrate transported through phloem to sink tissues like nodules, where it is metabolized by either sucrose synthase (SuSy) or alkaline invertase (AI) and the breakdown of sucrose into glucose and fructose, are essential proteins in plant life (Aleman et al, 2010;Mariana et al, 2013).The higher sucrose synthase activity observed in the nodules of bold seeded cultivars ensures hexose supply for meeting the energy and reducing power demands of nodules during the stage of active nitrogen fixation and probably may regulate carbon metabolism and nitrogen fixation (Chopra et al, 2003). In present investigation bold seeded cultivars showed higher status of PEP, MDH and IDH enzymes that indicate the utilization of glycolytic products for bacteroid respiration.…”

“…Legume nodules are primarily dependent on the import and metabolism of sucrose to provide the energy and carbon skeletons for biological nitrogen fixation (Gordon et al, 1999). Photosynthates predominantly in the form of sucrose are translocated to nodules and are metabolized by cytosolic invertase and/or sucrose synthase (Aleman et al, 2010). Chopra et al, (1998) reported that alkaline invertase to be the major enzyme of sucrose metabolism.…”