Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 5.06

PHENOTYPIC AND MOLECULAR CHARACTERIZATION OF ARABIDOPSIS DOUBLE MUTANT nia1, nia2 IN RESPONSE TO PATHOGEN ATTACK

F. ZANINOTTO, M.C. ROMERO-PUERTAS, M. DE STEFANO, M. DELLEDONNE

Università degli Studi di Verona, Dipartimento Scientifico e Tecnologico, Strada Le Grazie 15, 37134 Verona

nitrate reductase, nitric oxide, hypersensitive response

Nitric oxide (NO) is an inorganic free radical that act as a signaling molecule with multiple biological functions in vertebrates and in higher plants. NO acts as a key signal in plants resistant to incompatible pathogens by triggering resistance-associated cell death. Two enzymatic sources of NO in plants has been reported, NO synthase (NOS) and nitrate reductase (NR). NR is a central enzyme of nitrogen assimilation catalyzing the transfer of two electrons from NAD(P)H to nitrate to produce nitrite. It may also catalyze a one electron transfer from NAD(P)H to O₂ to produce superoxide anion and from NAD(P)H to nitrite to produce NO.

It has been shown that NR double mutants nia1,nia2 have greatly diminished NR activity and display very poor growth on media with nitrate as the only source of nitrogen.

Arabidopsis plants, both wild type and double mutants nia1, nia2, were grown in a grown chamber in short day conditions for 6-8 weeks. Ammonium sulfate 1 mM was added to mutants as source of nitrate. The response of double mutants against virulent and avirulent pathogen has been studied and compared to that of wild type. DAB and trypan blue staining have been used to measure oxidative burst and cell death, respectively. No difference were found in terms of hypersensitive response (HR) to avirulent pathogen between mutants and wild type plants. Moreover, defense-related genes induction after infection has been studied (gst, pal, pr1). From the analysis of the data obtained results, NR does not appear to be a necessary component of the HR.