Auxin signaling modulates redox-status in Arabidopsis thaliana.

IGLESIAS, MARÍA JOSE; TERRILE, MARÍA CECILIA; BARTOLI, CARLOS GUILLERMO; CASALONGUE, CLAUDIA ANAHI

San Pablo

Congreso; VII Meeting of the SFRBM-South American Group; 2011

SFRBM-South American Group

The survival of plants to adverse conditions involves the accurate perception and transduction of environmental signals to switch on defense and adaptative responses. Key elements in the adaptative response to abiotic stress seem to be hormone induced changes in growth and morphology, as well as stress-affected gradients of reactive oxygen species (ROS) and antioxidants. Auxin is a plant hormone that plays a pivotal role in many processes throughout the plant life cycle. The aim of our work is to characterise the participation of auxin signaling in the antioxidant system regulation during the plant defense response against environmental stress. We have previously reported that Arabidopsis double mutant for auxin receptors, tir1 afb2 displays increased tolerance against salinity evidenced by increased germination rate, root elongation and chlorophyll content. We have also demonstrated that tir1 afb2 plants showed reduced ROS accumulation (H2O2, O2-) as well as high levels of ascorbic acid and antioxidant enzymatic activities (ascorbate peroxidase, catalase, glutathione-S-transferase) when grows under salinity. To deep in the auxin regulation of antioxidant metabolism, we analyze ascorbate and glutathione (GSH) synthesis in plants subjected to exogenous auxin, indole acetic acid (IAA) application. We study the pattern of expression of GSH1 gene, encoding the first enzyme in GSH biosynthesis by utilizing the Arabidopsis ProGSH1:GUS (for b-glucuronidase) transgenic line. IAA treatments significantly inhibit the activity of this reporter line in a dose-response manner. Similar results were obtained from RT-PCR analysis when ascorbic synthesis genes, vtc2 (AT4G26850) and gldh (AT3G47930) were evaluated. These data suggest that auxin could modulate redox status at least through down-regulation of antioxidant biosynthesis. The cross-talk between auxin and redox signalings is emerging as a new regulatory node by which plants control growth and developmental processes. Partially supported by CONICET; UNMDP; ANPCyT.