Trans‐dominant suppression of plant TGA factors reveals their negative and positive roles in plant defense responses

• Published in: The Plant journal : for cell and molecular biology 2001-09, Vol.27 (6), p.529-538
• Main Authors: Pontier, Dominique, Miao, Zhong‐He, Lam, Eric
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial plant pathogens; Basic-Leucine Zipper Transcription Factors; Biological and medical sciences; DNA-Binding Proteins - genetics; Fundamental and applied biological sciences. Psychology; GNT35 gene; GSTs; Immunity, Innate - genetics; Leucine Zippers - genetics; Models, Genetic; Molecular Sequence Data; Nicotiana - genetics; Nicotiana tabacum; NPR1 protein; Nuclear Proteins; Pathology. Damages, economic importance; Phytopathology. Animal pests. Plant and forest protection; Plant Diseases - genetics; Plant Proteins - genetics; Plants, Genetically Modified; Plants, Toxic; salicylic acid; Salicylic Acid - metabolism; Signal Transduction; STR246 gene; stress responses; Suppression, Genetic; systemic acquired resistance; TGA transcription factors; Transcription Factors - genetics; trans‐dominant negative mutant
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.2001.01086.x

Summary Salicylic acid (SA) is a key regulator for the induction of systemic acquired resistance (SAR), and NPR1 is a critical mediator for the biological effects of SA. Physical interactions between NPR1 and TGA factors, a conserved family of basic‐leucine‐zipper (bZip) proteins in plants, have suggested a role for these transcription factors in mediating SAR induction via the regulation of defense genes. To elucidate this function, we constructed a trans‐dominant mutant that specifically eliminates DNA‐binding activities of this class of bZip proteins in transgenic tobacco plants. Our results demonstrate that the loss of TGA DNA‐binding activities is correlated with suppression of two xenobiotic‐responsive genes, GNT35 and STR246, and enhanced induction of pathogenesis‐related (PR) genes by SA. In addition, these TGA‐suppressed plants exhibited higher levels of PR gene induction by pathogen challenge and an enhanced SAR. These results suggest that TGA transcription factors serve both negative and positive regulatory roles in mediating plant defense responses.