Getting to the Root of Selenium Hyperaccumulation—Localization and Speciation of Root Selenium and Its Effects on Nematodes

Abstract

Elemental hyperaccumulation protects plants from many aboveground herbivores. Little is known about effects of hyperaccumulation on belowground herbivores or their ecological interactions. To examine effects of plant selenium (Se) hyperaccumulation on nematode root herbivory, we investigated spatial distribution and speciation of Se in hyperaccumulator roots using X-ray microprobe analysis, and effects of root Se concentration on root-associated nematode communities. Perennial hyperaccumulators Stanleya pinnata and Astragalus bisulcatus, collected from a natural seleniferous grassland contained 100–1500 mg Se kg−1 root dry weight (DW). Selenium was concentrated in the cortex and epidermis of hyperaccumulator roots, with lower levels in the stele. The accumulated Se consisted of organic (C-Se-C) compounds, indistinguishable from methyl-selenocysteine. The field-collected roots yielded 5–400 nematodes g−1 DW in Baermann funnel extraction, with no correlation between root Se concentration and nematode densities. Even roots containing > 1000 mg Se kg−1 DW yielded herbivorous nematodes. However, greenhouse-grown S. pinnata plants treated with Se had fewer total nematodes than those without Se. Thus, while root Se hyperaccumulation may protect plants from non-specialist herbivorous nematodes, Se-resistant nematode taxa appear to associate with hyperaccumulators in seleniferous habitats, and may utilize high-Se hyperaccumulator roots as food source. These findings give new insight into the ecological implications of plant Se (hyper)accumulation.

Selenium Effect Threshold for Soil Nematodes Under Rice Biofortification

“…Se-induced changes in soil nematodes were attributed to omnivorous and predatory nematodes, which could respond quickly to the high-Se stress. In another study (Prins et al, 2019 ), selenate treatment (80 μM, twice a week) significantly decreased nematode abundance in the rhizosphere soil of the Se-hyperaccumulator plant Stanleya pinnata . However, Se was only regarded as a pollutant in the above studies.…”

Keep and promote biodiversity at polluted sites under phytomanagement

“…Nonetheless, for a biodiversity assessment with more ecological relevance, it is desirable to include taxonomic groups from the different levels of the trophic chain. As a matter of fact, we should study as many taxonomic groups from the food web as possible (Garrouj et al 2018;Ali et al 2019;Prins et al 2019).…”

Transcriptomic analysis of selenium accumulation in Puccinellia distans (Jacq.) Parl., a boron hyperaccumulator

“…However, Se is beneficial for plant growth and is associated with increased antioxidant activity at low tissue levels (10 mg kg À1 ) (Mora et al, 2015). Plants also use Se as an elemental defense against certain herbivores, fungal pathogens and nematodes (Hanson et al, 2003(Hanson et al, , 2004Freeman et al, 2007Freeman et al, , 2009Quinn et al, 2010;Prins et al, 2019). Thus, Se provides ecological advantages to plants.…”