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While the uptake, assimilation, and regulation of sulfate metabolism have been extensively studied in C3 plants, specifically in Arabidopsis, less is known in C4 plants. Here, we describe our efforts to identify key genes involved in sulfate metabolism in the model C4 monocot Setaria viridis. Setaria viridis is an emerging model C4 grass due to its rapid life cycle, short stature, high seed production, and rapidly expanding genetic and genomic resources. Its close phylogenetic relationship with economically important crops, including maize and sorghum, and its relatively small genome make S. viridis an ideal system for rapidly discovering and characterizing agronomically important genes. To identify genes important for seed sulfur content, we performed a genome-wide association study by measuring total seed sulfur in a diversity panel consisting of 250 resequenced S. viridis lines. Our preliminary results show significant natural variation in seed sulfur accumulation within S. viridis. The most significant polymorphism identified by our screen is associated with a decrease in seed sulfur content and candidate genes underlying this GWA peak were previously shown to be involved in heat and water stress tolerance. Subsequent GWA studies using bioclimatic data found that the same polymorphisms are associated with lines collected in warmer, drier climates. Taken together, our results suggest a link between seed sulfur content and adaptation to warmer, drier climates in S. viridis.
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