title: Enhancing sucrose synthase activity in transgenic potato (Solanum tuberosum L.) tubers results in increased levels of starch, ADPglucose and UDPglucose and total yield.
abstract: Sucrose synthase (SuSy) is a highly regulated cytosolic enzyme that catalyzes the conversion of sucrose and a nucleoside diphosphate into the corresponding nucleoside diphosphate glucose and fructose. To determine the impact of SuSy activity in starch metabolism and yield in potato (Solanum tuberosum L.) tubers we measured sugar levels and enzyme activities in tubers of SuSy-overexpressing potato plants grown in greenhouse and open field conditions. We also transcriptionally characterized tubers of SuSy-overexpressing and -antisensed potato plants. SuSy-overexpressing tubers exhibited a substantial increase in starch, UDPglucose and ADPglucose content when compared with controls. Tuber dry weight, starch content per plant and total yield of SuSy-overexpressing tubers increased significantly over those of control plants. In contrast, activities of enzymes directly involved in starch metabolism in SuSy-overexpressing tubers were normal when compared with controls. Transcriptomic analyses using POCI arrays and the MapMan software revealed that changes in SuSy activity affect the expression of genes involved in multiple biological processes, but not that of genes directly involved in starch metabolism. These analyses also revealed a reverse correlation between the expressions of acid invertase and SuSy-encoding genes, indicating that the balance between SuSy- and acid invertase-mediated sucrolytic pathways is a major determinant of starch accumulation in potato tubers. Results presented in this work show that SuSy strongly determines the intracellular levels of UDPglucose, ADPglucose and starch, and total yield in potato tubers. We also show that enhancement of SuSy activity represents a useful strategy for increasing starch accumulation and yield in potato tubers.
authors.affiliation: Instituto de Agrobiotecnología (CSIC/UPNA/Gobierno de Navarra), Mutiloako etorbidea z/g, Nafarroa, Spain.
authors.forename: Edurne
authors.initials: E
authors.lastname: Baroja-Fernández
authors.forename: Francisco José
authors.initials: FJ
authors.lastname: Muñoz
authors.forename: Manuel
authors.initials: M
authors.lastname: Montero
authors.forename: Ed
authors.initials: E
authors.lastname: Etxeberria
authors.forename: María Teresa
authors.initials: MT
authors.lastname: Sesma
authors.forename: Miroslav
authors.initials: M
authors.lastname: Ovecka
authors.forename: Abdellatif
authors.initials: A
authors.lastname: Bahaji
authors.forename: Ignacio
authors.initials: I
authors.lastname: Ezquer
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Salomé
authors.initials: S
authors.lastname: Prat
authors.forename: Javier
authors.initials: J
authors.lastname: Pozueta-Romero
mesh_terms: D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000032:analysis / Q000096:biosynthesis*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D035281:Plant Tubers / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics; D013213:Starch / Q000032:analysis / Q000096:biosynthesis*
chemical_list: D010940:Plant Proteins; D018749:RNA, Plant; D013213:Starch; D005964:Glucosyltransferases; C022699:sucrose synthase; D005947:Glucose