Selenium Hyperaccumulator Plants Stanleya pinnata and Astragalus bisulcatus Are Colonized by Se-Resistant, Se-Excluding Wasp and Beetle Seed Herbivores
- California State Univ. (CalState), Fresno, CA (United States). Dept. of Biology; NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States). Intrinsyx Technologies Corporation and Space Biosciences
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
- Rothamsted Research, Harpenden, Hertfordshire (United Kingdom)
- Colorado State Univ., Fort Collins, CO (United States). Biology Dept.
Selenium (Se) hyperaccumulator plants can concentrate the toxic element Se up to 1% of shoot (DW) which is known to protect hyperaccumulator plants from generalist herbivores. There is evidence for Se-resistant insect herbivores capable of feeding upon hyperaccumulators. In this study, resistance to Se was investigated in seed chalcids and seed beetles found consuming seeds inside pods of Se-hyperaccumulator species Astragalus bisulcatus and Stanleya pinnata. Selenium accumulation, localization and speciation were determined in seeds collected from hyperaccumulators in a seleniferous habitat and in seed herbivores. Astragalus bisulcatus seeds were consumed by seed beetle larvae (Acanthoscelides fraterculus Horn, Coleoptera: Bruchidae) and seed chalcid larvae (Bruchophagus mexicanus, Hymenoptera: Eurytomidae). Stanleya pinnata seeds were consumed by an unidentified seed chalcid larva. Micro X-ray absorption near-edge structure (mXANES) and micro-X-Ray Fluorescence mapping (mXRF) demonstrated Se was mostly organic C-Se-C forms in seeds of both hyperaccumulators, and S. pinnata seeds contained ,24% elemental Se. Liquid chromatography–mass spectrometry of Secompounds in S. pinnata seeds detected the C-Se-C compound seleno-cystathionine while previous studies of A. bisulcatus seeds detected the C-Se-C compounds methyl-selenocysteine and c-glutamyl-methyl-selenocysteine. Micro-XRF and mXANES revealed Se ingested from hyperaccumulator seeds redistributed throughout seed herbivore tissues, and portions of seed C-Se-C were biotransformed into selenocysteine, selenocystine, selenodiglutathione, selenate and selenite. Astragalus bisulcatus seeds contained on average 5,750 mg Se g21 , however adult beetles and adult chalcid wasps emerging from A. bisulcatus seed pods contained 4–6 mg Se g21 . Stanleya pinnata seeds contained 1,329 mg Se g21 on average; however chalcid wasp larvae and adults emerging from S. pinnata seed pods contained 9 and 47 mg Se g21 . The results suggest Se resistant seed herbivores exclude Se, greatly reducing tissue accumulation; this explains their ability to consume high-Se seeds without suffering toxicity, allowing them to occupy the unique niche offered by Se hyperaccumulator plants.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER). Earth and Environmental Systems Science Division
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1627564
- Journal Information:
- PLoS ONE, Vol. 7, Issue 12; ISSN 1932-6203
- Publisher:
- Public Library of ScienceCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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