Two new isoforms of soybean thioredoxin-h and the response to oxidative stress

CRELIER, A., PAGANO, E. AND WOLOSIUK, R.A.

Mar del Plata

Congreso; XLIII Reunión Nacional de la SAIB; 2007

Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular

Thioredoxins (Trx) are ubiquitous small (ca. 12 KDa) proteins characterized by the conserved motif –WCGPC– that participates actively in thiol-disulfide exchange with other proteins. Among the plethora of plant Trx (20 isoforms in Arabidopsis), cytosol Trx-h (9 isoforms) play an important role in the tolerance to oxidative stress even though the contribution of individual isoforms is barely known. On the basis of known nucleotide sequences of plant orthologues, we designed oligonucleotides that were employed in the amplification by RT-PCR of mRNA prepared from mature soybean leaves. We isolated two open reading frames that were 87 % and 98 % identical to pea Trx-h1 and Trx-h4, respectively, but only 75 % and 71 % identical to Arabidopsis Trx-h1 and Trx-h2, respectively. Subsequently, we constructed specific oligonucleotides that matched the internal region of mature Trx-h for using in the RT-PCR analysis of gene differential expression. When different tissues were subjected to oxidants (e.g. H2O2, methyl viologen), the expression of Trx-h4 relative to soybean Trx-h1 not only was higher in non-photosynthetic tissues (seeds, roots) but also exhibited a different response. These results are in line with the view that soybean has developed mechanisms to tolerate the oxidative stress wherein isoforms of cytosol Trx-h play specific roles.