Intermediates of salicylic acid biosynthesis in tobacco

• Published in: Plant physiology (Bethesda) 1998-10, Vol.118 (2), p.565-572
• Main Authors: Ribnicky, D.M, Shulaev, V, Raskin, I
• Format: Article
• Language: English
• Subjects: Acetates; Agronomy. Soil science and plant productions; Alcohols; aldehydes; benzoic acid; benzylaldehyde; biochemical pathways; Biochemistry and Macromolecular Structure; Biological and medical sciences; Biosynthesis; cinnamic acid; disease resistance; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Generalities. Disease free stocks; Inoculation; Ions; Leaves; Lignin; Metabolism; metabolites; Nicotiana tabacum; Nitrogen metabolism and other ones (excepting carbon metabolism); Nutrition. Photosynthesis. Respiration. Metabolism; pathogenesis-related proteins; phenylpropanoid pathway; Phytopathology. Animal pests. Plant and forest protection; precursors; protein synthesis; RNA; Salicylates; salicylic acid; Tobacco mosaic virus; transcription (genetics); volatile compounds
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.118.2.565

Salicylic acid (SA) is an important component of systemic-acquired resistance in plants. It is synthesized from benzoic acid (BA) as part of the phenylpropanoid pathway. Benzaldehyde (BD), a potential intermediate of this pathway, was found in healthy and tobacco mosaic virus (TMV)-inoculated tobacco (Nicotiana tabacum L. cv Xanthi-nc) leaf tissue at 100 ng/g fresh weight concentrations as measured by gas chromatography-mass spectrometry. BD was also emitted as a volatile organic compound from tobacco tissues. Application of gaseous BD to plants enclosed in jars caused a 13-fold increase in SA concentration, induced the accumulation of the pathogenesis-related transcript PR-1, and increased the resistance of tobacco to TMV inoculation. [13C6]BD and [2H5]benzyl alcohol were converted to BA and SA. Labeling experiments using [13C1]Phe in temperature-shifted plants inoculated with the TMV showed high enrichment of cinnamic acids (72%), BA (34%), and SA (55%). The endogenous BD, however, contained nondetectable enrichment, suggesting that BD was not the intermediate between cinnamic acid and BA. These results show that BD and benzyl alcohol promote SA accumulation and expression of defense responses in tobacco, and provideinsight into the early steps of SA biosynthesis.