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Abstract Detail


Heavy Metals and Phytoremediation

Freeman, John L. [1], Quinn, Colin F. [2], Galeas, Miriam L. [2], Pilon-Smits, Elizabeth A.H. [2].

Evolutionary and Ecological Aspects of Selenium Hyperaccumulation.

Certain plants accumulate selenium (Se) to 1% of dry weight. We aim to obtain insight into how Se hyperaccumulation evolved, and how Se influences hyperaccumulator ecology. Our combined results from field and laboratory experiments, support the elemental defense hypothesis. Field studies showed that Se protects plants from prairie dogs and grasshoppers. In hyperaccumulator plants seasonal Se fluxes were uncoupled from sulfur, and different from non-accumulators. In spring and summer, Se was transferred from root to shoot and from old to young leaves and seeds. The Se was stored in roots over winter. The high Se in young leaves and seeds may have a role in defense. Hyperaccumulators concentrated Se as methylselenocysteine (MeSeCys) in trichomes or epidermal cells. Nonaccumulators showed no compartmentation. Se accumulation in the leaf periphery may both improve Se tolerance and serve as an elemental defense. While deterring generalist herbivores, Se hyperaccumulation can lead to the evolution of specialist, Se-tolerant herbivores. A tolerant variety of diamondback moth (DBM, P. xylostella) was found to thrive on hyperaccumulator Stanleya pinnata. The moth was Se-tolerant and had no feeding or oviposition preference for plants with or without Se. In contrast, Se deterred feeding and oviposition and was lethal at low levels to a common population of DBM. A microgastrine wasp, D. insulare, was found to parasitize the Se-tolerant moth. The Se-tolerant DBM and its parasitic wasp accumulated MeSeCys, the less toxic form also found in S. pinnata, while the Se- sensitive moth accumulated selenocysteine. The latter is toxic due to its misincorporation in protein, offering insight into the Se tolerance mechanism in this moth.


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Related Links:
Elizabeth Pilon-Smits laboratory web page


1 - Colorado State University, Biology Department, Program in Molecular Plant Biology, 1878 Campus Delivery, Fort Collins, CO, 80523, USA
2 - Colorado State University, Biology Department, Program in Molecular Plant Biology

Keywords:
Selenium Hyperaccumulation
evolution
Phytotoxicity
Tolerance
Elemental Defense
Biotransformation
Se fluxes in troposheres.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P05009
Abstract ID:389


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