ABA INCREASES TOTAL IRON CONTENT IN ARABIDOPSIS PLANTS GROWING UNDER IRON DEFICIENT CONDITIONS.

RAMÍREZ, LEONOR; LAMATTINA LORENZO

Rosario, Santa Fe

Congreso; Reunión Argentina de Fisiología Vegetal; 2008

Sociedad Argentina de Fisiología Vegetal

Iron is a transition metal and, its ability to gain and lose one electron confers it important properties for redox reactions. Iron takes part in proteins that are essential for photosynthesis, respiration, DNA synthesis and hormone production. It is mainly present as ferric ion, which is poorly soluble in neutral to alkaline soils. In these conditions, plants (except the grasses) sense low iron availability and induce a set of responses named strategy I: (i) ATPase-mediated acidification of the rhizosphere, (ii) enhanced activity and expression of a plasma membrane-bound reductase (FRO2), (iii) increased expression of a Fe2+ transporter (IRT1) and (iv) root hair proliferation. It is well known that the responses to different stresses are often mediated by transduction pathways which involve the plant hormone abscisic acid (ABA). The purpose of this research was to study the role of ABA during iron deficiency in Arabidopsis thaliana. Plants were grown for 10 days, and then were transferred for 3 days to iron-sufficient (50 M FeEDTA) or iron-deficient (0 M FeEDTA) medium, with or without exogenous ABA treatment. We found that iron content increases in plants treated with ABA, irrespective of the plant iron nutritional status. We also found that mRNA accumulation of FRO2, IRT1 and the transcription factor FIT1 and root ferric-chelate reductase activity were repressed in response to ABA. These results lead us to hypothesize that ABA-treated plants could be sensing a normal iron status and then blocking the expression of iron uptake-associated genes. In parallel, ABA treatment increased root hair density, indicating no correlation between root hair proliferation and expression of iron uptake genes. Finally, experiments are in progress to know: i) how is the iron uptake influenced by ABA and ii) how the levels of ABA change in plants growing under deficient iron conditions. Supported by CONICET, ANPCyT, UNMdP.