BRASSINOSTEROIDS-ETHYLENE INTERACTION FOR THE REGULATION OF ASCORBIC ACID SYNTHESIS IN TOMATO LEAVES

MAZORRA, LUIS MIGUEL; SENN, MARÍA EUGENIA; GERGOFF GROZEFF, G.E.; FANELLO, DIEGO D.; CARRIÓN, CRISTIAN; NÚÑEZ, MIRIAM; BARTOLI, CARLOS G.; BISHOP, GERARD

Mar del Plata

Congreso; XXIX Reunión Argentina de Fisiología Vegetal; 2012

Sociedad Argentina de Fisiología Vegetal

The aim of our research is to gain better understanding of the hormonal control of ascorbic acid synthesis and accumulation in plants. We focused our analysis on the effect of plant steroid hormones (Brassinosteroids-BRs) on tomato (Solanum lycopersicum L. cv Ailsa Craig) leaves by utilising BRs deficient mutants (dx) and lines over-accumulating BRs (35S:D). Plants were grown at 300 µmol m-2 s-1 (PPFD) at 23 ºC for two weeks (16/8hr light/dark, respectively). Leaves from the dx plants showed lower ascorbic acid content and reduced capacity to synthesise ascorbic acid than non-modified tomato plants. 35S:D leaves have similar amount of ascorbic acid content to wild type but have a higher capacity to synthesise this metabolite. Ethylene production rates and its capacity of synthesis (i.e. ethylene production after incubation leaves with its precursor aminocyclopropane-1-carboxylic acid) was higher in dx but not in the 35S:D leaves compared with those that have normal BRs content. To study the participation of BRs in the ethylene-mediated antioxidant accumulation, plants were treated with the ethylene action inhibitor 1-methyl cyclopropene (1-MCP). This treatment was performed by placing plants in 40 L chambers containing 1µL L-1 1-MCP overnight. When ethylene signalling was blocked, ascorbic acid content and synthesis capacity enhanced twice in dx plants but decreased in 35S:D leaves. These results demonstrate that BRs and ethylene signalling pathways interact for the control of the level and synthesis capacity of ascorbic acid in leaves of tomato plants. Further analysis will be focused on the involvement of BRs regulation on photosynthesis and respiration metabolism including antioxidant accumulation.