Salt stress enhances xylem development and expression of S-adenosyl-L-methionine synthase in lignifying tissues of tomato plants

• Published in: Planta 2004-12, Vol.220 (2), p.278-285
• Main Authors: Sanchez-Aguayo, I, Rodriguez-Galan, J.M, Garcia, R, Torreblanca, J, Pardo, J.M
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biosynthesis; Cell walls; Environment; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Plant; Leaves; lignification; Lignin; Lignin - metabolism; Lycopersicon esculentum - cytology; Lycopersicon esculentum - drug effects; Lycopersicon esculentum - enzymology; Lycopersicon esculentum - growth & development; messenger RNA; methionine adenosyltransferase; Methionine Adenosyltransferase - biosynthesis; Methionine Adenosyltransferase - genetics; plant biochemistry; plant genetics; Plant Leaves - enzymology; Plant physiology and development; Plant roots; Plant Roots - enzymology; Plant Shoots - enzymology; Plant tissues; Plants; RNA; Roots; S-Adenosylmethionine - metabolism; Salinity; salt stress; Salts; Sodium Chloride - pharmacology; Solanum lycopersicum var. lycopersicum; Solutes; Stems; Tissue Distribution; Tomatoes; Up-Regulation; vegetable crops; Water and solutes. Absorption, translocation and permeability; Water transport; Xylem
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-004-1350-2

S-Adenosyl-L-methionine synthase (SAM; ATP:L-methionine adenosyltransferase, EC 2.5.1.6) catalyzes the biosynthesis of S-adenosyl-L-methionine (AdoMet), a universal methyl-group donor. This enzyme is induced by salinity stress in tomato (Lycopersicon esculentum Mill.). To elucidate the role of SAM and AdoMet in the adaptation of plants to a saline environment, the expression pattern and histological distribution of SAM was investigated in control and salt-stressed tomato plants. Immunohistochemical analysis showed that SAM proteins were expressed in all cell types and plant organs, albeit with preferential accumulation in lignified tissues. Lignin deposition was estimated by histochemical tests and the extent of tissue lignification in response to salinity was quantified by image analysis. The average number of lignified cells in vascular bundles was significantly greater in plants under salt stress, with a maximal expansion of the lignified area found in the root vasculature. Accordingly, the greatest abundance of SAM gene transcripts and proteins occurred in roots. These results indicate that increased SAM activity correlated with a greater deposition of lignin in the vascular tissues of plants under salinity stress. A model is proposed in which an increased number of lignified tracheary elements in tomato roots under salt stress may enhance the cell-to-cell pathway for water transport, which would impart greater selectivity and reduced ion uptake, and compensate for diminished bulk flow of water and solutes along the apoplastic pathway.