Contribution of Root Hair Development to Sulfate Uptake in Arabidopsis

Abstract

Root hairs often contribute to nutrient uptake from environments, but the contribution varies among nutrients. In <i>Arabidopsis</i>, two high-affinity sulfate transporters, SULTR1;1 and SULTR1;2, are responsible for sulfate uptake by roots. Their increased expression under sulfur deficiency (-S) stimulates sulfate uptake. Inspired by the higher and lower expression, respectively, of <i>SULTR1;1</i> in mutants with more (<i>werwolf</i> [<i>wer</i>]) and fewer (<i>caprice</i> [<i>cpc</i>]) root hairs, we examined the contribution of root hairs to sulfate uptake. Sulfate uptake rates were similar among plant lines under both sulfur sufficiency (+S) and -S. Under -S, the expression of <i>SULTR1;1</i> and <i>SULTR1;2</i> was negatively correlated with the number of root hairs. These results suggest that both -S-induced <i>SULTR</i> expression and sulfate uptake rates were independent of the number of root hairs. In addition, we observed (1) a negative correlation between primary root lengths and number of root hairs and (2) a greater number of root hairs under -S than under +S. These observations suggested that under both +S and -S, sulfate uptake was influenced by the root biomass rather than the number of root hairs.