The fascinating facets of plant selenium accumulation – biochemistry, physiology, evolution and ecology

Abstract

Contents 1582 I. 1582 II. 1583 III. 1588 IV. 1590 V. 1592 1592 References 1592 SUMMARY: The importance of selenium (Se) for medicine, industry and the environment is increasingly apparent. Se is essential for many species, including humans, but toxic at elevated concentrations. Plant Se accumulation and volatilization may be applied in crop biofortification and phytoremediation. Topics covered here include beneficial and toxic effects of Se on plants, mechanisms of Se accumulation and tolerance in plants and algae, Se hyperaccumulation, and ecological and evolutionary aspects of these processes. Plant species differ in the concentration and forms of Se accumulated, Se partitioning at the whole-plant and tissue levels, and the capacity to distinguish Se from sulfur. Mechanisms of Se hyperaccumulation and its adaptive significance appear to involve constitutive up-regulation of sulfate/selenate uptake and assimilation, associated with elevated concentrations of defense-related hormones. Hyperaccumulation has evolved independently in at least three plant families, probably as an elemental defense mechanism and perhaps mediating elemental allelopathy. Elevated plant Se protects plants from generalist herbivores and pathogens, but also gives rise to the evolution of Se-resistant specialists. Plant Se accumulation affects ecological interactions with herbivores, pollinators, neighboring plants, and microbes. Hyperaccumulation tends to negatively affect Se-sensitive ecological partners while facilitating Se-resistant partners, potentially affecting species composition and Se cycling in seleniferous ecosystems.

Agronomic biofortification with selenium impacts storage proteins in grains of upland rice

“…), which suggests an antagonism between S and Se. This is also consistent with the reduction in the concentration of S with Se fertilization reported in other plant species …”

“…No evidence exists for the essentiality of Se in higher plants but a number of beneficial effects of Se on plant physiology have been recognized in several plant species . Selenium can be acquired by plant roots as selenate or selenite, and from organic forms such as selenocysteine (SeCys) and selenomethionine (SeMet) .…”

“…Selenium (Se) is an essential micronutrient for humans and animals . However, the concentration of Se in soils and foods varies greatly .…”

“…Selenium (Se) is an essential micronutrient for humans and animals . However, the concentration of Se in soils and foods varies greatly . The recommended daily intake of Se is 55 μg kg −1 for human adults .…”

Cytokinin at the Crossroads of Abiotic Stress Signalling Pathways

“…Selenate and selenite, the two major forms of selenium that are found in the environment, are readily absorbed by plants via sulphate and phosphate transporters, respectively [73]. In this respect, cytokinin-regulated sulphate and Pi pathways might form a point of cross-talk between selenium and cytokinin signalling.…”