title: Selenium accumulation protects plants from herbivory by Orthoptera via toxicity and deterrence.
abstract: To investigate whether selenium (Se) accumulation in plants provides a chemical defense against generalist insect herbivores, the feeding preference and performance of a mix of orthopteran species were investigated. The selenium hyperaccumulator Stanleya pinnata and accumulator Brassica juncea were used in herbivory studies in the laboratory, and S. pinnata was also used in a manipulative field experiment. In laboratory studies, both crickets and grasshoppers avoided plants pretreated with selenate, while those given no choice died after eating leaves with elevated Se (447 +/- 68 and 230 +/- 68 microg Se g(-1) DW, respectively). B. juncea has previously been shown to accumulate selenate, while S. pinnata hyperaccumulates methyl-selenocysteine. Thus, these findings demonstrate that both inorganic and organic forms of selenium protect plants from herbivory. Grasshoppers fed S. pinnata contained methylselenocysteine in their midgut and absorbed this form into surrounding tissues. In a manipulative field experiment, methylselenocysteine protected S. pinnata from invertebrate herbivory and increased its long-term survival rate over an entire growth season. * In native habitats of selenium hyperaccumulators, orthopterans represent a major group of insect herbivores. Protection offered by organic selenium accumulation against these herbivores may have promoted the evolution of selenium hyperaccumulation in plants.
authors.affiliation: Biology Department, Program in Molecular Plant Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: John L
authors.initials: JL
authors.lastname: Freeman
authors.affiliation: Biology Department, Program in Molecular Plant Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Stormy Dawn
authors.initials: SD
authors.lastname: Lindblom
authors.affiliation: Biology Department, Program in Molecular Plant Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Colin F
authors.initials: CF
authors.lastname: Quinn
authors.affiliation: Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA.
authors.forename: Sirine
authors.initials: S
authors.lastname: Fakra
authors.affiliation: Advanced Light Source, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Marcus
authors.affiliation: Biology Department, Program in Molecular Plant Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Elizabeth A H
authors.initials: EAH
authors.lastname: Pilon-Smits
mesh_terms: D000818:Animals; D027883:Astragalus Plant / Q000378:metabolism*; D019607:Brassicaceae / Q000378:metabolism*; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D017753:Ecosystem; D016566:Organoselenium Compounds / Q000378:metabolism* / Q000633:toxicity; D009987:Orthoptera / Q000187:drug effects; D018515:Plant Leaves; D012643:Selenium / Q000378:metabolism* / Q000633:toxicity; D017279:Selenocysteine / Q000031:analogs & derivatives
chemical_list: D016566:Organoselenium Compounds; D017279:Selenocysteine; D012643:Selenium; D003545:Cysteine; C002979:selenomethylselenocysteine