ROL OF FITNESS TRANSCRIPTION FACTOR IN ABIOTIC AND BIOTIC STRESS RELATED PROCESSES

VALLE, EM;; ZANOR, MI; MENGARELLI, DIEGO

Buenos Aires

Congreso; Reuniòn Conjunta de Sociedades de Biociencias; 2017

SAIB

The uncharacterized transcription factor FITNESS is highly repressed by oxidative stress. Knock-out lines (fitness) showed higher tolerance to oxidative stress generated in the chloroplast and to salt stress due to decreased levels of ROS. When analyzed at metabolic level fitness lines showed an increment of salicylic acid (SA). In plants, the major route of SA synthesis is the isochorismate (IC) synthase pathway. ICS1 transcripts were significantly increased in fitness mutants. SA accumulation is maintained through transcriptional regulation of EDS1 (ENHANCED DISEASE SUSCEPTIBILITY 1) and PAD4 (PHYTOALEXIN DEFICIENT 4) and also rise of endogenous SA correlates with pathogenesis-related genes induction. Transcriptional reprogramming is controlled mainly by NPR1 (non expressor of pathogenesis-related gene 1). Monomerization and nuclear accumulation of NPR1 in the presence of SA results in PR1 increased expression and is therefore considered a marker for activation of salicylate-signalling pathway. Consistent with the increased levels of SA measured in fitness mutants we observed an induction of both NPR1 and PR1 transcript levels. The finding that PAD4 and EDS1 transcripts are both up-regulated in fitness mutants confirms that the ROS perturbation leads to modification of hormonal homeostasis. Our data indicate that altered expression of FITNESS acts modulating SA-related processes: fitness lines show a high transcriptional up-regulation of the SA-responsive marker gene PR1, whose expression is NPR1-dependent. Also, fitness lines resulted less sensitive to Pseudomona syringae pv. tomato DC 3000 infection. Therefore, we postulate that FITNESS acts regulating signal transduction pathways in response to both abiotic and biotic stresses.