INVESTIGADORES
GIORDANO Carla Valeria
congresos y reuniones científicas
Título:
Impact of solar UV-B on DNA integrity in Gunnera magellanica, a native plant of Tierra del Fuego, southern Argentina
Autor/es:
GIORDANO C. V.; ZIMA A. M.; HERRERA M. V.; ROUSSEAUX M. C.; SCOPEL A. L.; BALLARÉ C. L.; CALDWELL M. M.
Lugar:
Snowbird, USA
Reunión:
Congreso; 85th Annual Meeting of the Ecological Society of America; 2000
Resumen:
The natural ecosystems of Tierra del Fuego (55oS) are seasonaly subjected to elevated UV-B (280-315 nm) fluxes due to the passage of the Antarctic ozone “hole” during the spring. We are studing the effects of the enhanced UV-B doses on native plants communities of the Tierra del Fuego National Park. Gunnera magellanica is a perennial herb that restarts its growth during the early spring, and occupies open areas in shrub-dominated plant communities. These two features make this plant potentially susceptible to springtime increments in solar UV-B. Recent findings of our group show that the expansion of Gunnera magellanica leaves is reduced by solar UV-B. The growth inhibition is accompanied by increased DNA damage (measured as cyclobutane pyrimidine dimers, CPD). Analysis of field samples shows that the steady state level of DNA damage at midday correlates with the pre-midday UV-B dose, which varies in response to ozone fluctuations. In 1998 and 1999, we carried out field and laboratory experiments to estimate the DNA repair capacity of Gunnera magellanica. Our results show that leaves of this plant are capable of  repairing in a light-dependent manner c. 50% of the initial content of CPD in one hour, at 25 oC. This photorepair rate is in the lower end of the range of values reported for plants of temperate species such as soybean, alfalfa, cucumber, rice, sorghum and wheat. A low photorepair rate might be one of the factors that explains why there is a high correlation between UV-B doses and DNA damage in Gunnera magellanica, in spite of the fact that the leaves of this plant are loaded with high quantities of UV-absorbing phenolic sunscreens. The combination of molecular techniques with ecophysiological experiments in the field will allow us to better understand the biological impact of enhanced UV-B on the native flora of this region.