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Roles of rhizobial symbionts in selenium hyperaccumulation in Astragalus (Fabaceae)
Author(s) -
Alford Élan R.,
Lindblom Stormy D.,
Pittarello Marco,
Freeman John L.,
Fakra Sirine C.,
Marcus Matthew A.,
Broeckling Corey,
PilonSmits Elizabeth A. H.,
Paschke Mark W.
Publication year - 2014
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.1400223
Subject(s) - biology , fabaceae , astragalus , botany , selenium , symbiosis , bacteria , genetics , medicine , alternative medicine , materials science , pathology , traditional chinese medicine , metallurgy
• Premise of the study: Are there dimensions of symbiotic root interactions that are overlooked because plant mineral nutrition is the foundation and, perhaps too often, the sole explanation through which we view these relationships? In this paper we investigate how the root nodule symbiosis in selenium (Se) hyperaccumulator and nonaccumulator Astragalus species influences plant selenium (Se) accumulation. • Methods: In greenhouse studies, Se was added to nodulated and nonnodulated hyperaccumulator and nonaccumulator Astragalus plants, followed by investigation of nitrogen (N)–Se relationships. Selenium speciation was also investigated, using x‐ray microprobe analysis and liquid chromatography–mass spectrometry (LC‐MS). • Key results: Nodulation enhanced biomass production and Se to S ratio in both hyperaccumulator and nonaccumulator plants. The hyperaccumulator contained more Se when nodulated, while the nonaccumulator contained less S when nodulated. Shoot [Se] was positively correlated with shoot N in Se‐hyperaccumulator species, but not in nonhyperaccumulator species. The x‐ray microprobe analysis showed that hyperaccumulators contain significantly higher amounts of organic Se than nonhyperaccumulators. LC‐MS of A. bisulcatus leaves revealed that nodulated plants contained more γ‐glutamyl‐methylselenocysteine (γ‐Glu‐MeSeCys) than nonnodulated plants, while MeSeCys levels were similar. • Conclusions: Root nodule mutualism positively affects Se hyperaccumulation in Astragalus . The microbial N supply particularly appears to contribute glutamate for the formation of γ‐Glu‐MeSeCys. Our results provide insight into the significance of symbiotic interactions in plant adaptation to edaphic conditions. Specifically, our findings illustrate that the importance of these relationships are not limited to alleviating macronutrient deficiencies.