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

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 5.13

ATCYS FROM ARABIDOPSIS THALIANA ENCODES A CYSTEINE-PROTEASE INHIBITOR THAT FUNCTIONS AS A NEGATIVE REGULATOR OF HYPERSENSITIVE CELL DEATH

BELENGHI B., PERAZZOLLI M., DELLEDONNE M.

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

massimo.delledonne@univr.it

cysteine protease inhibitors, nitric oxide, hypersensitive cell death, plant-pathogen interaction

In plants, cysteine protease inhibitors (cystatins) are involved in the regulation of protein turnover and play an important role in resistance against insects and pathogens. The genome of Arabidopsis most likely contains no more than two cystatins. We have identified and characterized one member of this family (Atcys) which encodes a protein of 102 amino acids and contains the conserved motif of the cystatin superfamily (gln-val-val-ala-gly). Atcys was constitutively expressed in roots and in developing siliques. In leaves, it was strongly induced by wounding, by challenge with avirulent pathogens and by nitric oxide (NO). Overexpression of Atcys blocked cell death activated by either avirulent pathogens or by oxidative and nitrosative stress in both Arabidopsis suspension cultured cells and in transgenic tobacco plants. However, the drastic inhibition of hypersensitive cell death following infection with the avirulent pathogen did not reduce the host capacity to control the spread of pathogenic infection, suggesting that Atcys has a role in plant defense. Furthermore, the observed inhibition of NO-mediated cell death in Atcys overexpressors indicated that NO is not cytotoxic for the plant and functions as cell death trigger through the stimulation of an active process, in which cysteine proteases appear to play a crucial role.