Activation of a diverse set of genes during the tobacco resistance response to TMV is independent of salicylic acid; induction of a subset is also ethylene independent

• Published in: The Plant journal : for cell and molecular biology Vol. 21; no. 5; pp. 409 - 418
• Main Authors: Guo, Ailan, Salih, Gaza, Klessig, Daniel F.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.03.2000; Blackwell Science
• Subjects: Biological and medical sciences; Ethylenes - pharmacology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - drug effects; Gene Expression Regulation, Plant - physiology; Gene Expression Regulation, Viral - drug effects; Gene Expression Regulation, Viral - physiology; Genes, sis; Nicotiana - genetics; Nicotiana - virology; Nicotiana tabacum; PAL gene; Pathology. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Plant viruses and viroids; Plants, Genetically Modified; Plants, Toxic; PR-1 gene; salicylic acid; Salicylic Acid - pharmacology; SIS gene; Tobacco mosaic virus; Tobacco Mosaic Virus - physiology; Salicylic acid; Plant pathogen; Hypersensitivity; Ethylene; Stimulant plant; Activation; Gene expression; Nicotiana tabacum; Host virus relation; Virus; Infection; Disease resistance; Regulation(control); Sensitivity resistance; Dicotyledones; Angiospermae; Plant growth substance; Defense mechanism; Spermatophyta; Solanaceae
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313x.2000.00692.x

Summary Through differential screening of a cDNA library, we cloned six groups of genes that are expressed relatively early in the inoculated leaves of tobacco resisting infection by tobacco mosaic virus (TMV). Induction of all these genes was subsequently detected in the uninoculated leaves; thus, their expression is associated with the development of both local and systemic acquired resistance. Exogenously applied salicylic acid (SA) was observed to induce these genes transiently. However, analyses with transgenic NahG plants, which are unable to accumulate SA, demonstrated that expression of these genes in TMV‐inoculated leaves is mediated via an SA‐independent pathway. Because the expression kinetics of these genes differ from those associated with the well‐characterized pathogenesis‐related protein (PR‐1) and phenylalanine ammonia‐lyase (PAL) genes, we propose that they belong to a group which we designate SIS, for SA‐independent, systemically induced genes. Interestingly, the expression of several SIS genes in the uninoculated leaves of TMV‐infected NahG plants was delayed and/or reduced, raising the possibility that SA is involved in activating some of these genes in systemic tissue. Most of the SIS genes were induced by exogenous ethylene. However, analyses of infected NahG plants treated with ethylene action and/or synthesis inhibitors indicated that the TMV‐induced expression of several SIS genes is independent of ethylene as well as SA.