DNA repair capacity of a native plant of Tierra del Fuego, southern Argentina, in its natural environment

GIORDANO C. V.; ZIMA A. M.; HERRERA M. V.; ROUSSEAUX M. C.; SCOPEL A. L.; BALLARÉ C. L.; CALDWELL M. M.

Mar del Plata, Argentina

Workshop; SPARC 2000, Associated Workshop: Impacts of UV radiation on terrestrial and acquatic ecosystems; 2000

DNA molecules are modified by ultraviolet B radiation (UV-B), which produces two major forms of aberrant bases or photoproducts: cyclobutane pyrimidine dimers (CPDs), and pyrimidine (6-4) pyrimidone dimers. These photoproducts stop DNA replication and transcription, and they are repaired to permit the normal functioning of the cell, by two general mechanisms: excision repair and photorrepair (driven by blue and UV-A photons). We are studying the effects of solar UV-B on a native plant in Tierra del Fuego (55oS), Gunnera magellanica, which is subjected to seasonal increments of solar UV-B due to the passage of the “ozone hole” over this region during the spring. We found that leaf expansion rate in Gunnera magellanica is reduced by UV-B. This growth inhibition is accompanied by increased DNA damage, and the CPD load at noon correlates with pre-middday UV-B dose. We performed field and laboratory experiments  to asses the photorrepair capacity of Gunnera magellanica in its natural environment, to further understand the relationships between the UV climate and DNA damage dynamics. Our results show that Gunnera magellanica repairs its DNA in a light dependent manner. Preliminary results indicate that this photorrepair rate is in the lower end of the range of values reported for temperate species. This low repair rate can be one of the factors that explains the high correlation between UV-B doses and DNA damage in Gunnera magellanica. The combination of field and laboratory experiments will give valuable information  to understand the effects of enhanced solar UV-B radiation on the native flora of this region.