title: Low-temperature effect on enzyme activities involved in sucrose-starch partitioning in salt-stressed and salt-acclimated cotyledons of quinoa (Chenopodium quinoa Willd.) seedlings.
abstract: The effect of low temperature on growth, sucrose-starch partitioning and related enzymes in salt-stressed and salt-acclimated cotyledons of quinoa (Chenopodium quinoa Willd.) was studied. The growth of cotyledons and growing axes in seedlings grown at 25/20 degrees C (light/dark) and shifted to 5/5 degrees C was lower than in those only growing at 25/20 degrees C (unstressed). However, there were no significant differences between low-temperature control and salt-treated seedlings. The higher activities of sucrose phosphate synthase (SPS, EC 2.4.1.14) and soluble acid invertase (acid INV, EC 3.2.1.25) were observed in salt-stressed cotyledons; however, the highest acid INV activity was observed in unstressed cotyledons. ADP-glucose pyrophosphorylase (ADP-GPPase, EC 2.7.7.27) was higher in unstressed cotyledons than in stressed ones. However, between 0 and 4days the highest value was observed in salt-stressed cotyledons. The lowest value of ADP-GPPase was observed in salt-acclimated cotyledons. Low temperature also affected sucrose synthase (SuSy, EC 2.4.1.13) activity in salt-treated cotyledons. Sucrose and glucose were higher in salt-stressed cotyledons, but fructose was essentially higher in low-temperature control. Starch was higher in low-temperature control; however, the highest content was observed at 0day in salt-acclimated cotyledons. Results demonstrated that low temperature induces different responses on sucrose-starch partitioning in salt-stressed and salt-acclimated cotyledons. Data also suggest that in salt-treated cotyledons source-sink relations (SSR) are changed in order to supply soluble sugars and proline for the osmotic adjustment. Relationships between starch formation and SuSy activity are also discussed.
authors.affiliation: Cátedra de Fisiología Vegetal, Facultad de Ciencias Naturales e IML, Miguel Lillo 205, CP 4000, San Miguel de Tucumán, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Rosa
authors.forename: Mirna
authors.initials: M
authors.lastname: Hilal
authors.forename: Juan A
authors.initials: JA
authors.lastname: González
authors.forename: Fernando E
authors.initials: FE
authors.lastname: Prado
mesh_terms: D027465:Chenopodium quinoa / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D003080:Cold Temperature; D018548:Cotyledon / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000378:metabolism; D005964:Glucosyltransferases / Q000378:metabolism; D012492:Salts / Q000494:pharmacology; D013213:Starch / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism*
chemical_list: D012492:Salts; D013395:Sucrose; D013213:Starch; D005964:Glucosyltransferases; C022699:sucrose synthase; C022698:sucrose-phosphate synthase; D051599:Glucose-1-Phosphate Adenylyltransferase