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Title: Elemental concentrations in the seed of mutants and natural variants of Arabidopsis thaliana grown under varying soil conditions

Author
item MCDOWELL, STEPHEN - University Of Nevada
item AKMAKJIAN, GARO - University Of California
item SLADEK, CHRIS - University Of Nevada
item MENDOZA-COZATL, DAVID - University Of Missouri
item SAINI, NICK - University Of Nevada
item Baxter, Ivan
item GUERINOT, MARY LOU - Dartmouth College
item HARPER, JEFFREY - University Of Nevada

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2013
Publication Date: 5/6/2013
Publication URL: http://handle.nal.usda.gov/10113/56680
Citation: McDowell, S.C., Akmakjian, G., Sladek, C., Mendoza-Cozatl, D., Saini, N., Baxter, I.R., Guerinot, M., Harper, J.F. 2013. Elemental concentrations in the seed of mutants and natural variants of Arabidopsis thaliana grown under varying soil conditions. PLoS One. 8(5):e63014.

Interpretive Summary: Understanding how plants regulate element composition of tissues is critical for agriculture, the environment, and human health. Sustainably meeting the increasing food and biofuel demands of the planet will require growing crops with fewer inputs such as the primary macronutrients phosphorus (P) and potassium (K). Ionomics is the study of elemental accumulation in living systems using high-throughput elemental profiling. With this technique, we can rapidly generate large quantities of data on thousands of samples, allowing for the profiling of large genetic mapping populations and the discovery of hundreds of loci important for elemental accumulation. We have used this approach to study the seeds of a panel of mutants and to sample the natural diversity present in collections of a model plant, the wild mustard Arabidopsis. We find that the elemental composition of a plant is tightly controlled by its genes and by the soil conditions under which it is grown. This suggests that crop varieties developed for improved elemental uptake and accumulation will be highly environment specific. These findings contribute to a novel strategy to improve the productivity of all major crops thus impacting world food security in a positive fashion.

Technical Abstract: The concentrations of mineral nutrients in seeds are critical to both the life cycle of plants as well as human nutrition. These concentrations are strongly influenced by soil conditions, as shown here by quantifying the concentration of 14 elements in seeds from Arabidopsis thaliana plants grown under four different soil conditions: standard, or modified with NaCl, heavy metals, or alkali. Each of the modified soils resulted in a unique change to the seed ionome (the mineral nutrient content of the seeds). To help identify the genetic networks regulating the seed ionome, changes in elemental concentrations were evaluated using mutants corresponding to 760 genes as well as 10 naturally occurring accessions. The frequency of ionomic phenotypes supports an estimate that much as 11% of the A. thaliana genome encodes proteins of functional relevance to ion homeostasis in seeds. A subset of mutants were analyzed with two independent alleles, providing five examples of genes important for regulation of the seed ionome: SOS2, ABH1, CCC, At3g14280 and CNGC2. In a comparison of nine different accessions to a Col-0 reference, eight accessions were observed to have reproducible differences in elemental concentrations, seven of which were dependent on specific soil conditions. These results indicate that the A. thaliana seed ionome is distinct from the vegetative ionome, and that elemental analysis is a sensitive approach to identify genes controlling ion homeostasis, including those that regulate gene expression, phospho-regulation, and ion transport.