Cadmium Tolerance in Transgenic Arabidosis thaliana overexpressing Brassica napus Thioredoxin f

PINA JI; STOLOWICZ FABIANA; PAGANO E; WOLOSIUK RA

Mendoza

Congreso; http://www.saib.org.ar/paginas/2006/biocell,%20suplement%202005.pdf; 2005

SAIB

Thioredoxins (Trx) are ubiquitous small proteins (ca. 12 kDa) involved in the regulation of the thiol-disulphide status of target enzymes. In higher plants chloroplasts, two types of Trx (m and f) would participate not only in the modulation of chloroplast enzymes but also in the response to oxidative stress. Heavy metals are among the highly toxic compounds for cells whose action would rely on mechanisms of oxidative stress. In this context, the Cd regulation of Trx gene expression and the inhibition of Trxs activities by Cd was reported in Chlamydomonas reinhartii and E. coli but there was little information about the relationship bettween Trxs and heavy metals in higher plants. To analyze this alternative, we constructed, via Agrobacterium transformation, transgenic Arabidopsis thaliana plants overexpressing Brassica napus Trx-f and subsequently evaluated the action of Cd over germination, initial and mature growth. No differences were found between normal and transgenic seeds in the percentage of germination. At variance, the rate of radicule growth in transgenic lines was much higher than in the wild type counterpart. Notably, mature plants of the former (50d) accumulated in green tissues higher levels of Cd that the latter upon exposition for 5d to 1mM Cd in the hydroponic solution. The response of mature transgenic lines overexpressing Trx-f was phenotypically different from the normal counterpart. Although the underlying mechanisms are still unknown, these results are the first experimental indication of a link between the leaf Trx system and the oxidative stress elicited by heavy metals