Knockout analysis of Arabidopsis transcription factors TGA2, TGA5, and TGA6 reveals their redundant and essential roles in systemic acquired resistance.
Arabidopsis nonexpresser of pathogenesis-related (PR) genes (NPR1) is the sole positive regulator that has been shown to be essential for the induction of systemic acquired resistance. In npr1 mutant plants, salicylic acid (SA)-mediated PR gene expression and pathogen resistance are abolished completely. NPR1 has been shown to interact with three closely related TGA transcription factors-TGA2, TGA5, and TGA6-in yeast two-hybrid assays. To elucidate the biological functions of these three TGA transcription factors, we analyzed single and combined deletion knockout mutants of TGA2, TGA5, and TGA6 for SA-induced PR gene expression and pathogen resistance. Induction of PR gene expression and pathogen resistance by the SA analog 2,6-dichloroisonicotinic acid (INA) was blocked in tga6-1 tga2-1 tga5-1 but not in tga6-1 or tga2-1 tga5-1 plants. Loss of INA-induced resistance to Peronospora parasitica Noco2 cosegregated with the tga6-1 mutation in progeny of multiple lines that were heterozygous for tga6-1 and homozygous for tga2-1 tga5-1 and could be complemented by genomic clones of wild-type TGA2 or TGA5, indicating that TGA2, TGA5, and TGA6 encode redundant and essential functions in the positive regulation of systemic acquired resistance. In addition, tga6-1 tga2-1 tga5-1 plants had reduced tolerance to high levels of SA and accumulated higher basal levels of PR-1 under noninducing conditions, suggesting that these TGA factors also are important for SA tolerance and the negative regulation of the basal expression of PR-1.
Zhang
Yuelin
Y
Biotechnology Laboratory, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada. yuelin@interchange.ubc.ca
Tessaro
Mark J
MJ
Lassner
Michael
M
Li
Xin
X
D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005658:Fungi / Q000254:growth & development; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007113:Immunity, Innate / Q000187:drug effects / Q000235:genetics; D007539:Isonicotinic Acids / Q000494:pharmacology; D009154:Mutation; D009687:Nuclear Proteins; D010935:Plant Diseases / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D020156:Salicylic Acid / Q000633:toxicity; D015398:Signal Transduction / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
C489413:AHBP-1b protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D007539:Isonicotinic Acids; D009687:Nuclear Proteins; D010940:Plant Proteins; C107090:TGA6 protein, Arabidopsis; D014157:Transcription Factors; C053376:pathogenesis-related proteins, plant; C068757:HBP-1b protein, plant; C077262:PR-1 protein, Arabidopsis; C077261:2,6-dichloroisonicotinic acid; D020156:Salicylic Acid