Choline synthesis in spinach in relation to salt stress

• Published in: Plant physiology (Bethesda) Vol. 103; no. 4; pp. 1269 - 1276
• Main Authors: Summers, P.S, Weretilnyk, E.A
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-12-1993
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; Agronomy. Soil science and plant productions; Aldehydes; BETAINA; BETAINE; Betaines; Biological and medical sciences; BIOSINTESIS; BIOSYNTHESE; Biosynthesis; CHOLINE; COLINA; Environmental and Stress Physiology; Enzymes; ESTRES; FEUILLE; Fundamental and applied biological sciences. Psychology; HOJAS; Leaves; Peas; Phosphatases; Physiological regulation; Plant physiology and development; SALINIDAD; SALINITE; Spinach; SPINACIA OLERACEA; STRESS; VIA BIOQUIMICA DEL METABOLISMO; VOIE BIOCHIMIQUE DU METABOLISME; Water and solutes. Absorption, translocation and permeability; Water salinization; Radiolabelling; Enzyme; Transferases; Phosphoric monoester hydrolases; Esterases; Biosynthesis; Plant leaf; Spinacia oleracea; Metabolism; Stress; Chenopodiaceae; Salinity; Vegetable crop; Enzymatic activity; Betaine; Dicotyledones; Choline; Angiospermae; Plant tissue disc; Hydrolases; Spermatophyta; Choline kinase; Ethanolamine kinase
• DOI: 10.1104/pp.103.4.1269
• EISSN: 1532-2548
• ISSN: 0032-0889

Choline metabolism was examined in spinach (Spinacia oleracea L.) plants growing under nonsaline and saline conditions. In spinach, choline is required for phosphatidylcholine synthesis and as a precursor for the compatible osmolyte glycine betaine (betaine). When control (nonsalinized) leaf discs were incubated for up to 2 h with [1,2-14C]ethanolamine, label appeared in the N-methylated derivatives of phosphoethanolamine including phosphomono-, phosphodi-, and phosphotri- (i.e. phosphocholine) methylethanolamine, as well as in choline and betaine, whereas no radioactivity could be detected in the mono- and dimethylated derivatives of the free base ethanolamine. Leaf discs from salinized plants showed the same pattern of labeling, although the proportion of label that accumulated in betaine was almost 3-fold higher in the salinized leaf discs. Enzymes involved in choline metabolism were assayed in crude leaf extracts of plants. The activities of ethanolamine kinase and of the three S-adenosylmethionine:phospho-base N-methyltransferase enzymes responsible for N-methylating phosphoethanolamine to phosphocholine were all higher in extracts of plants salinized step-wise to 100, 200, or 300 mM NaCl compared with controls. In contrast, choline kinase, phosphocholine phosphatase, and cytidine, 5'-triphosphate: phosphocholine cytidylyltransferase activities showed little variation with salt stress. Thus, the increased diversion of choline to betaine in salt-stressed spinach appears to be mediated by the increased activity of several key enzymes involved in choline biosynthesis