Identification of an immediate-early salicylic acid-inducible tobacco gene and characterization of induction by other compounds

Tobacco genes that are induced in response to salicylic acid (SA) treatment with immediate-early kinetics were identified by differential mRNA display. Detailed analysis of IS10a, one cDNA clone identified by this method, revealed induction within 30 min of treatment, with a peak of expression at 3 h, that decayed rapidly thereafter. Treatment with the protein synthesis inhibitor, cycloheximide (CHX), also caused induction of IS10a mRNA to comparable levels, but the IS10a mRNA continued to accumulate after 3 h of induction. In combination, CHX and SA led to a superinduction of IS10a mRNA levels that was also sustained. Half-maximal induction was evident at ca. 100–150 M SA. In addition to SA, induction of IS10a occurred to varying degrees upon treatment with acetylsalicylic acid, benzoic acid, 2,4-dichlorophenoxyacetic acid, methyl jasmonate, and hydrogen peroxide, whereas treatment with other compounds had no effect. The proteins encoded by IS10a and a second highly homologous cDNA show sequence similarity to UDP-glucose: flavonoid glucosyltransferases.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - 4HBA 4-hydroxybenzoic acid - aa amino acid - bp base pair - nt nucleotide - ASA acetyl salicylic acid - BA benzoic acid - CHX Cycloheximide - MJ methyl jasmonate - PCR polymerase chain reaction - SA salicylic acid - TMV tobacco mosaic virus