Analysis of carbohydrate metabolism enzymes and cellular contents of sugars and proteins during spruce somatic embryogenesis suggests a regulatory role of exogenous sucrose in embryo development

• Published in: Journal of experimental botany Vol. 52; no. 365; pp. 2301 - 2311
• Main Authors: Iraqi, Driss, Tremblay, Francine M.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.12.2001; OXFORD UNIVERSITY PRESS
• Subjects: administration & dosage; analysis; beta-Fructofuranosidase; Biological and medical sciences; Biotechnology; Carbohydrate Metabolism; chemical constituents of plants; culture media; embryo (plant); Embryogenesis; Embryos; Enzymes; enzymology; Eukaryotic cell cultures; fructose; Fundamental and applied biological sciences. Psychology; glucose; Glucosyltransferases; Glucosyltransferases - metabolism; Glycoside Hydrolases; Glycoside Hydrolases - metabolism; growth & development; Hexoses; Hexoses - metabolism; In vitro propagation: entire plant regeneration from tissues and cell cultures; invertase; metabolism; Methods. Procedures. Technologies; Picea; Picea - enzymology; Picea - growth & development; Picea - metabolism; Picea glauca; Picea mariana; Plant cells and fungal cells; Plant physiology and development; plant proteins; Plants; Proteins; Proteins - metabolism; Regulation of Growth, Development and Whole Organism Physiology; Seeds; Seeds - enzymology; Seeds - growth & development; Seeds - metabolism; Somatic embryogenesis; Somatic embryos; Starch; Starch - metabolism; Starches; sucrose; Sucrose - administration & dosage; Sucrose - analysis; sucrose phosphate synthase; sucrose synthase; Sugars; tissue culture; Tissue cultures, protoplasts; β-Fructofuranosidase; Glycosyltransferases; Glucose; Sucrose-phosphate synthase; Somatic embryo; Regulation(control); Enzymatic activity; Softwood forest tree; Gymnospermae; Carbohydrate; Chemical concentration; Sucrose synthase; Picea mariana; Embryonic development; Picea glauca; Enzyme; Starch; Transferases; Metabolism; Fructose; Protein; Glycosidases; Hydrolases; Coniferales; Hexosyltransferases; Spermatophyta; O-Glycosidases
• DOI: 10.1093/jexbot/52.365.2301
• ISSN: 0022-0957

Carbohydrate metabolism was investigated during spruce somatic embryogenesis. During the period of maintenance corresponding to the active phase of embryogenic tissue growth, activities of soluble acid invertase and alkaline invertase increased together with cellular glucose and fructose levels. During the same time, sucrose phosphate synthase (SPS) activity increased while sucrose synthase (SuSy) activity stayed constant together with the cellular sucrose level. Therefore, during maintenance, invertases were thought to generate the hexoses necessary for embryogenic tissue growth while SuSy and SPS would allow cellular sucrose to be kept at a constant level. During maturation on sucrose‐containing medium, SuSy and SPS activities stayed constant whereas invertase activities were high during the early stage of maturation before declining markedly from the second to the fifth week. This decrease of invertase activities resulted in a decreased hexose:sucrose ratio accompanied by starch and protein deposition. Additionally, carbohydrate metabolism was strongly modified when sucrose in the maturation medium was replaced by equimolar concentrations of glucose and fructose. Essentially, during the first 2 weeks, invertase activities were low in tissues growing on hexose‐containing medium while cellular glucose and fructose levels increased. During the same period, SuSy activity increased while the SPS activity stayed constant together with the cellular sucrose level. This metabolism reorganization on hexose‐containing medium affected cellular protein and starch levels resulting in a decrease of embryo number and quality. These results provide new knowledge on carbohydrate metabolism during spruce somatic embryogenesis and suggest a regulatory role of exogenous sucrose in embryo development.