T11 AM Aquatic Plants: Methods, Mechanisms and Markers
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 343-344

(GRE-1117-737934) Molecular and physiological responses of the aquatic plant Lemna gibba to metals and PAHs.

Akhtar, Tariq ¹, Lees, Hazel¹, Lampi, Mark¹, Greenberg, Bruce ¹, ¹ Department of Biology, University of Waterloo, Waterloo, ON, Canada

ABSTRACT- Lemna gibba can assimilate contaminants from the aquatic phases of the environment in which it resides. We have examined the mechanisms of how metals and polycyclic aromatic hydrocarbons exert their toxicity on this higher aquatic plant. It was found that copper, cadmium and 1,2-dihydroxyanthraquinone (1,2-dhATQ) negatively impact Lemna gibba, at relatively low levels. Further, they are synergistically toxic via a reactive oxygen species mechanism. We have now examined how Lemna gibba responds to these contaminants at a molecular and physiological level. Specifically, both copper and 1,2-dhATQ appeared to disrupt photosynthetic electron transport causing an overall reduced plastoquionone pool. We further demonstrate that the redox state of the plastoquinone pool can effectively trigger a variety of stress responses. In particular, copper and 1,2-dhATQ causes numerous changes in gene expression as well as accumulation of flavonoids, which could both be traced back to a reduced plastoquinone pool. Interestingly, by oxidizing the plastoquinone pool many of these responses were reversed. Other environmental stresses such as temperature fluctuations and UV-B radiation effectively caused similar stress responses in concert with a reduced plastoquinone pool. We therefore conclude that the redox balance of the cell (possibly via the plastoquinone pool) acts as a general sensor for environmental stress in Lemna gibba.

Key words: Redox balance, Electron transport, Flavonoids, Gene expression