Micro-analytical and molecular approaches for understanding the distribution, biochemistry, and molecular biology of selenium in (hyperaccumulator) plants

Main conclusion: Micro-analytical techniques to untangle Se distribution and chemical speciation in plants coupled with molecular biology analysis enable the deciphering of metabolic pathways responsible for Se tolerance and accumulation. Abstract: Selenium (Se) is not essential for plants and is toxic at high concentrations. However, Se hyperaccumulator plants have evolved strategies to both tolerate and accumulate > 1000 µg Se g⁻¹ DW in their living above-ground tissues. Given the complexity of the biochemistry of Se, various approaches have been adopted to study Se metabolism in plants. These include X-ray-based techniques for assessing distribution and chemical speciation of Se, and molecular biology techniques to identify genes implicated in Se uptake, transport, and assimilation. This review presents these techniques, synthesises the current state of knowledge on Se metabolism in plants, and highlights future directions for research into Se (hyper)accumulation and tolerance. We conclude that powerful insights may be gained from coupling information on the distribution and chemical speciation of Se to genome-scale studies to identify gene functions and molecular mechanisms that underpin Se tolerance and accumulation in these ecologically and biotechnologically important plants species. The study of Se metabolism is challenging and is a useful testbed for developing novel analytical approaches that are potentially more widely applicable to the study of the regulation of a wide range of metal(loid)s in hyperaccumulator plants. Graphical Abstract: [Figure not available: see fulltext.]