Enhanced Resistance of atbzip62 against Pseudomonas syringae pv. tomato Suggests Negative Regulation of Plant Basal Defense and Systemic Acquired Resistance by AtbZIP62 Transcription Factor

The intrinsic defense mechanisms of plants toward pathogenic bacteria have been widely investigated for years and are still at the center of interest in plant biosciences research. This study investigated the role of the gene encoding a transcription factor (TF) in the basal defense and systemic acquired resistance in Arabidopsis using the reverse genetics approach. To achieve that, the mutant line (lacking the gene) was challenged with pv. ( ) inoculated by infiltration into Arabidopsis leaves at the rosette stage. The results indicated that plants showed an enhanced resistance phenotype toward over time compared to Col-0 and the susceptible disease controls, and In addition, the transcript accumulation of pathogenesis-related genes, and , increased significantly in over time (0-72 h post-inoculation, hpi) compared to that of and (susceptible lines), with prevailing over . When coupled with the recorded pathogen growth (expressed as a colony-forming unit, CFU mL ), the induction of genes, associated with the salicylic acid (SA) defense signaling, in part explained the observed enhanced resistance of mutant plants in response to . Furthermore, when was inoculated, the expression of was upregulated in the systemic leaves of Col-0, while that of remained at a basal level in Col-0. Moreover, the expression of (a systemic acquired resistance -related) gene was significantly upregulated at all time points (0-24 h post-inoculation, hpi) in compared to Col-0 and and . Under the same conditions, exhibited a high transcript accumulation level 48 hpi in the background. Therefore, all data put together suggest that and coupled with and , with prevailing over , would contribute to the recorded enhanced resistance phenotype of the mutant line against . Thus, the TF is proposed as a negative regulator of basal defense and systemic acquired resistance in plants under infection.