Characterization of the Arabidopsis iss1 and trp5 mutants reveals a link between tryptophan metabolism and sulfur availability
Embargo Date
2026-05-08
OA Version
Citation
Abstract
As agriculture practices intensify in response to a growing world population, the depletion of essential soil nutrients has created a need for sustainable solutions. One such nutrient is sulfur. Sulfur deficiency can have a series of cascading reactions negatively impacting plant health and overall fitness, including but not limited to decreased hormone and defense compound levels. This research investigates the effects of sulfur deficiency on the plant tryptophan (Trp) metabolic pathway, which is studied for its specialized metabolites including indole-3-acetic acid (IAA) and indole glucosinolates (IGs). IAA, a plant growth hormone found universally across plant species, and IGs are sulfur-rich anti-herbivory compounds limited to the Brassicaceae including Arabidopsis thaliana, the species used for these studies. In this thesis, RNA sequencing (RNA-seq) and differential gene expression (DGE) analysis of the iss1, trp5, and iss1trp5 mutants suggested potential genetic links between photosynthesis regulation, sulfur metabolism pathways, and Trp biosynthesis and catabolism. These findings prompted further investigation into the underlying regulatory mechanisms of the Trp pathway. To gain a deeper understanding of potential regulatory mechanisms of Trp metabolism, chlorophyll production was quantified and analyzed via UV-Vis spectrophotometry in wild-type, iss1, trp5, and iss1trp5 mutant plants in response to sulfur starvation conditions in comparison to a normal growth condition. Reverse-phase HPLC quantification of glucosinolates was also completed to gain insight into the large effects of sulfur starvation on the Trp pathway. Under control conditions, both the iss1 and trp5 mutants showed increased chlorophyll production compared to wild-type (WT). Additionally, and in response to sulfur starvation, iss1 and iss1trp5 showed an increase in chlorophyll production compared to control conditions while the trp5 mutant expressed a decrease in chlorophyll production with sulfur starvation. Taken together, these results suggested that iss1trp5 may use the tryptophan independent (Trp-I) branch as a compensatory pathway to regulate Trp metabolism in response to sulfur starvation. These studies offer greater insight into how plants’ metabolic regulation in response to nutrient deficiencies.
Description
2024
License
Attribution 4.0 International