Induction of benzoic acid 2-hydroxylase in virus-inoculated tobacco

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Plant Physiology; (United States)

OSTI ID:5815140

Leon, J; Yalpani, N; Raskin, I; Lawton, M A ^[1]

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1. Rutgers Univ., New Brunswick, NJ (United States)

Salicylic acid (SA) plays an important role in the induction of plant resistance to pathogens. An accompanying article shows that SA is synthesized via the decarboxylation of cinnamic acid to benzoic acid (BA), which is, in turn, hydroxylated to SA. Leaf extracts of tobacco catalyze the 2-hydroxylation of Ba to SA. The monooxygenase catalyzing this reaction, benzoic acid 2-hydroxylase (BA2H), required NAD(P)H or reduced methyl viologen as an electron donor. BA2H activity was detected in healthy tobacco leaf extracts (1-2 nmol h[sup [minus]1] g[sup [minus]1] fresh weight) and was significantly increased upon inoculation with tobacco mosaic virus (TMV). This increase paralleled the levels of free SA in the leaves. Induction of BA2H activity was restricted to tissue expressing a hypersensitive response at 24[degrees]C. TMV induction of BA2H activity and Sa accumulation were inhibited when inoculated tobacco plants were incubated for 4 d at 32[degrees]C and then transferred to 24[degrees]C, they showed a 15-fold increase in BA2H activity and a 65-fold increase in free SA content compared with healthy plants incubated at 24[degrees]C. Treatment of leaf tissue with the protein synthesis inhibitor cycloheximide blocked the induction of BA2H activity by TMV. The effect of TMV inoculation on BA2H could be duplicated by infiltrating leaf discs of healthy plants with BA. This response was observed even when applied levels of BA were much lower than the levels observed in vivo after virus inoculation. Feeding tobacco leaves with phenylalanine, cinnamic acid, or o-coumaric acid (putative precursors of SA) failed to trigger the induction of BA2H activity. BA2H appears to be a pathogen-inducible protein with an important regulatory role in SA accumulation during the development of induced resistance to TMV in tobacco. 33 refs., 6 figs., 3 tabs.

• DOE Contract Number: FG05-91ER20049
• OSTI ID: 5815140
• Journal Information: Plant Physiology; (United States), Vol. 103:2; ISSN 0032-0889
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
DISEASE RESISTANCE
BIOLOGICAL PATHWAYS
HYDROXYLASES
ECOLOGICAL CONCENTRATION
SALICYLIC ACID
BIOSYNTHESIS
TOBACCO
BENZOIC ACID
CINNAMIC ACID
CYCLOHEXIMIDE
IN VIVO
LEAVES
PATHOGENS
PHENYLALANINE
TOBACCO MOSAIC VIRUS
AMINO ACIDS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
CARBOXYLIC ACIDS
DRUGS
ENZYMES
FUNGICIDES
HYDROXY ACIDS
MICROORGANISMS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PARASITES
PESTICIDES
PROTEINS
SYNTHESIS
VIRUSES
550200* - Biochemistry