Selenium hyperaccumulation offers protection from cell disruptor herbivores

Area of Science:

• Plant Science
• Ecology
• Biochemistry

Background:

• Hyperaccumulation of toxic trace elements is a plant defense mechanism.
• Selenium (Se) hyperaccumulation protects plants against herbivores and pathogens.
• Se sequestering in leaf periphery may influence herbivore susceptibility.

Purpose of the Study:

• Investigate Se's protective role in Stanleya pinnata and Astragalus bisulcatus.
• Assess defense against cell-disrupting herbivores: western flower thrips and two-spotted spider mites.

Main Methods:

• Comparative herbivory assays on high-Se vs. low-Se plants.
• Spider mite population studies on Se-treated plants.
• Selenium distribution and speciation using μXRF and X-ray absorption spectroscopy.

Main Results:

• Plants with high Se concentrations ( > 650 mg/kg) showed less thrips herbivory than low-Se plants ( < 150 mg/kg).
• Spider mites preferred low-Se plants and avoided high-Se plants; populations decreased on Se-treated plants.
• Spider mites accumulated methylselenocysteine, a non-toxic Se form, even at high plant Se levels (up to 200 mg/kg).

Conclusions:

• First study showing Se protects against cell-disrupting herbivores.
• Results support the elemental defense hypothesis for Se.
• Findings have implications for agriculture and management of Se-rich crops against economically important pests.