Apoplastic expression of yeast-derived invertase in potato: effects on photosynthesis, leaf solute composition, water relations, and tuber composition

• Published in: Plant physiology (Bethesda) Vol. 100; no. 1; pp. 301 - 308
• Main Authors: Heineke, D, Sonnewald, U, Bussis, D, Gunter, G, Leidreiter, K, Wilke, I, Raschke, K, Willmitzer, L, Heldt, H.W
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.09.1992
• Subjects: ACIDE AMINE; Agronomy. Soil science and plant productions; Amino acids; AMINOACIDOS; ANATOMIA DE LA PLANTA; ANATOMIE VEGETALE; Biological and medical sciences; Biotechnology; FEUILLE; FLOEMA; FOTOSINTESIS; FRUCTOFURANOSIDASA; FRUCTOFURANOSIDASE; FRUCTOSA; FRUCTOSE; Fundamental and applied biological sciences. Psychology; GENE; GENES; GLUCOSA; GLUCOSE; HOJAS; Leaves; Metabolism; Metabolism and Enzymology; Metabolism. Physicochemical requirements; METABOLISME DES GLUCIDES; METABOLISMO DE CARBOHIDRATOS; Phloem; PHLOEME; PHOTOSYNTHESE; Photosynthesis; Plant physiology and development; Plants; PRESION OSMOTICA; PRESSION OSMOTIQUE; SACCHAROMYCES CEREVISIAE; SACCHAROSE; Sap; SAVIA; SEVE; SOLANUM TUBEROSUM; Starches; SUCROSA; TRANSFERENCIA DE GENES; TRANSFERT DE GENE; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE; Transgenic plants; TUBERCULE; TUBERCULO; Tubers; Yeasts; Yeast; Sap; Growth; Transpiration; Water regime; Dicotyledones; Angiospermae; Transgenic plant; Chemical composition; Carbohydrate; Solanaceae; Conductive tissue; Chlorophyll; Genetic transformation; Enzyme; Solanum tuberosum; β-D-Fructofuranosidase; Plant leaf; Apoplast; Gene expression; Metabolism; Phenotype; Phloem; Vegetable crop; Photosynthetic pigment; Aminoacid; Spermatophyta; Tuber plant; Chimerism; Photosynthesis
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.100.1.301

In potato plants (Solanum tuberosum), a chimeric yeast-derived invertase gene fused to a 35S cauliflower mosaic virus promoter has been expressed. The protein was targeted to the cell wall by using the signal peptide of proteinase inhibitor if fused to the amino terminus of the yeast invertase. The transformed plants had crinkled leaves, showed a reduced growth rate, and produced fewer tubers. Although in the apoplast of the leaves of the transformed plants the content of glucose and fructose rose by a factor of 20, and that of sucrose declined 20-fold, 98% of the carbohydrate in the phloem sap consisted of sucrose, demonstrating the strong specificity of phloem loading. In the leaf cells of the transformed plants, glucose, fructose, and amino acids, especially proline, were accumulated. Consequently, the osmolality of the cell sap rose from 250 to 350 mosmol/kg. Our results show that the observed 75% decrease of photosynthesis is not caused by a feedback regulation of sucrose synthesis and is accompanied by an increase in the osmotic pressure in the leaf cells. In the transformed plants, not only the amino acid to sucrose ratio in the phloem sap, but also the amino acid and protein contents in the tubers were found to be elevated. In the tubers of the transformed plants, the protein to starch ratioincreased