Title: Selenium Hyperaccumulator Plants Stanleya pinnata and Astragalus bisulcatus Are Colonized by Se-Resistant, Se-Excluding Wasp and Beetle Seed Herbivores

Abstract

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,more » 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.« less

Authors:

Freeman, John L. ^[1]; Marcus, Matthew A. ^[2]; Fakra, Sirine C. ^[2]; Devonshire, Jean ^[3]; McGrath, Steve P. ^[3]; Quinn, Colin F. ^[4]; Pilon-Smits, Elizabeth A. H. ^[4]

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+ Show Author Affiliations

1. 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
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
3. Rothamsted Research, Harpenden, Hertfordshire (United Kingdom)
4. Colorado State Univ., Fort Collins, CO (United States). Biology Dept.

Publication Date:

Mon Dec 03 00:00:00 EST 2012

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER). Earth and Environmental Systems Science Division

OSTI Identifier:

1627564

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

PLoS ONE

Additional Journal Information:

Journal Volume: 7; Journal Issue: 12; Journal ID: ISSN 1932-6203

Publisher:

Public Library of Science

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; Science & Technology - Other Topics