CYANOBACTERIAL FLAVODOXIN GENE EXPRESSED IN TRANSPLASTOMIC PLANTS ALLOWS THE RECOVERY OF NORMAL PHENOTYPE IN A FERREDOXIN SILENCED BACKGROUND

NICOLÁS BLANCO, M. EUGENIA SEGRETIN, ROMINA CECCOLI, MOHAMMAD REZA HAJIREZAEI, NÉSTOR CARRILLO, FERNANDO BRAVO ALMONACID

Rosario, Santa Fe, Argentina

Congreso; XIII Reunión Latinoamericana y XXVII Reunión Argentina de Fisiología Vegetal; 2008

Sociedad Argentina de Fisiología Vegetal (SAFV)

In previous work it was demostrated that the Anabaena protein flavodoxin (Fld) expressed in transgenic plants was able to confer increased tolerance to multiple sources of biotic and abiotic stress. Endogenous levels of ferredoxin (Fd) decrease during the exposure of plants to those stress circumstances, and together with previous findings showing that Fld is able to mediate plant Fd-dependent reactions in vitro, these results indicate that Fld could compensate Fd decline. To further investigate this hypothesis, transgenic tobacco plants in which Fd levels were decreased as consequence of post transcriptional gene silencing (AV plants), were subjected to chloroplast genome transformation with Fld coding sequence. Chloroplast transformation was chosen because of the origin of Fld gene sequence (phylogenetically related to chloroplast genome) and the potentially higher levels of protein expression that can be obtained by this kind of transformation technique relative to nuclear transformation. To achieve this goal a vector named pBSWUTR was used. This vector targets the integration to the intergenic region between the genes 16S and trnI, both belonging to the rrn operon. Several independent lines of AV plants were subjected to transformation with pBSWUTR-Fld. After 2 - 3 regeneration rounds to reach the homoplasmic state, transplastomic plants expressing Anabaena Fld in their chloroplasts with very low expression of Fd were characterized at molecular, biochemical and physiological level (AV/UTRFld plants). As expected, Fld accumulated in the chloroplast of AV/UTRFld plants to higher levels than those observed in nuclear transformants. When compared to AV plants (with a strong chlorotic phenotype and a decreased photosynthetic perfomance), AV/UTRFld plants exhibited an almost total recovery of wild type phenotype. Results obtained as part of the characterization of these plants allow us to confirm that cyanobacterial Fld is able to substitute endogenous Fd in planta.