Transcriptomic analysis of early responses to salicylic acid in Arabidopsis
Holuigue, Loreto (A) Blanco, Francisca (A) Herrera, Ariel (A) Cecchini, Nicolas M (B) Salinas, Paula (A) Alvarez, Maria Elena (B) (A): Facultad de Ciencias Biologicas, Universidad Catolica de Chile, Santiago, Chile. (B): CIQUIBIC-CONICET, Universidad Nacional de Cordoba,
Salicylic acid (SA) is a key hormone of stress defenses responses induced by biotrophic pathogens and some abiotic stress in plants. Although important knowledge concerning SA mechanism has been obtained in the last years, the essential role that this hormone plays in stress defense is not well understood. To identify early SA-induced genes (SAIGs), expression profiles of wild type and npr1-1 mutant Arabidopsis seedlings in response to short treatments with SA were studied by using the Complete Arabidopsis Transcriptome MicroArray chip. We identified 217 early SAIGs; only a small proportion of them (24; 11%) use the NPR1-independent pathway. Analysis of the functional categories of these genes support the idea that SA is involved in the recovery of the cell redox balance, in intracellular stress signaling, in improving pathogen recognition, and in promoting metabolic changes. Expression analysis in response to an avirulent bacterial pathogen, performed for a selection of these genes, support involvement of early SAIGs in the pathogen-induced defense reaction. Search for over-represented promoter elements in all SAIGs identified and mechanistic analysis performed for a selection of these genes give us important clues concerning SA mechanism. Functional promoter analysis for glutaredoxin GRXC9 gene, one of the early SAIGs identified, allowed us to identify an as-1 element as the main SA-responsive element in this promoter. Supported by grants 1060494 from Fondecyt-CONICYT and 2005-7-186 from CONICYT/SECyT Cooperation Program.
