Graduate Student University of Georgia ATHENS, Georgia
Body of Abstract: Drought stress frequency and severity are predicted to increase due to the ongoing effects of climate change. This irregularity in water availability could impact ecosystem and agricultural productivity. Drought also affects mineral nutrient uptake which is critical to both plant growth and stress response. One such nutrient is sulfate which is taken up by the roots and transported via the vasculature to multiple tissues for assimilation. The transport of sulfate is mediated by a family of genes known as sulfate transporters (SULTR). It has been shown that sulfate concentration in the xylem sap of both crops and trees increases during drought and precedes the well-known drought stress hormone, ABA. This hints at sulfate as an early drought response signal. Whether SULTRs have an effect on the drought-sensitive increase of xylem sap sulfate and its overall regulation is not fully known. In poplar, subgroup 3 SULTRs (SULTR3) exhibit variable expression, with SULTR3;2 and SULTR3;4 showing preferential expression in the xylem tissue. Specifically, SULTR3;2 expression is induced during drought stress. This study aims to characterize the role of SULTR3s in poplar growth and drought stress. CRISPR-Cas9 was used to generate double and quadruple knockout mutants of xylem preferential SULTR3s. Plant growth was unaffected in the mutants relative to the control under either well-watered or chronic drought stress conditions in a greenhouse study. Under the chronic drought, xylem tissue of sultr3 mutants had altered secondary metabolite abundance in comparison to its well-watered counterpart. Ongoing experiments are investigating the xylem sap response of sultr3 mutants to acute drought. Results so far suggest that SULTR3;2 and SULTR3;4 are not critical for growth and primary metabolism but may influence secondary metabolism pathways for defense compound production in the xylem of poplar.