Universität zu Köln

Shukla, Varsa ORCID: 0009-0008-7785-2320 (2026). Adaptive potential of sulfate content in Arabidopsis thaliana. PhD thesis, Universität zu Köln.

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Abstract

Sulfur (S) is an essential macronutrient required for plant growth, metabolism, redox homeostasis, and defense, and its availability strongly constrains plant performance in both natural and agricultural systems. Plants exhibit substantial natural variation in sulfur content, for instance, Arabidopsis thaliana accessions show up to a six-fold difference in foliar sulfur (Baxter et al., 2007; Campos et al., 2021). Several genes, such as APR2, ATPS1, and OASC, were found to contribute to this variation; however, they explain only part of it, suggesting additional regulatory layers. Importantly, the functional significance of this variation and adaptive responses to sulfur limitation remain poorly understood. To address this gap, we analyzed Arabidopsis accessions grouped into low-, mid-, and high-foliar sulfur content using an integrated multi-omics and phenotyping framework under varying sulfate supply. Our study revealed that despite higher basal sulfate levels, high-S accessions experienced pronounced depletion of sulfur pools and incurred significant fitness costs under sulfur deficiency. The observed decline in foliar sulfate, total sulfur, and glutathione (GSH) was associated with reduced sulfate uptake and translocation to the shoots, as well as limited flux into GSH. These physiological changes were accompanied by a strong induction of sulfur-starvation marker genes and increased oxidative stress. Besides, high-S accessions also showed restricted growth, accelerated flowering, and altered sulfur nitrogen coordination, including repression of nitrate assimilation and broad metabolic reprogramming. In contrast, low-S accessions maintained sulfur pools and reproductive fitness under sulfur deficiency through enhanced sulfate uptake and translocation. Unlike the high-S group, low-S accessions prioritized redox homeostasis by channeling sulfur into glutathione synthesis, achieved through coordinated induction of genes involved in nitrate and cysteine assimilation. Coordinated induction of nitrate and cysteine assimilation pathways in the low-S group reflects increased utilization of nitrate and cysteine under sulfur deficiency. Mid-S accessions exhibited intermediate, context-dependent responses. We further explored transgenerational effects of sulfur deficiency and found that flowering time is sensitive to parental sulfur status, alongside other metabolic and developmental traits. Transcriptome profiling further supported these phenotypes, with high-S accessions showing substantially more differentially expressed genes under S-deficiency. Although core sulfur starvation responses were conserved, with 55 core DEGs shared across the group, most DEGs and enriched gene ontology terms were unique to groups, indicating divergent regulatory strategies. Together, these findings demonstrate that high basal sulfur content does not confer protection against sulfur limitation but instead reflects increased vulnerability under prolonged S-deficiency. Also, with our data, we can deduce that effective sulfur stress tolerance is achieved through coordinated regulation of sulfur acquisition, metabolic fluxes, redox balance, and development, as exemplified by low-S accessions.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Shukla, Varsa vshukla@uni-koeln.de https://orcid.org/0009-0008-7785-2320 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-805171
Date:	2026
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Biology > Botanical Institute
Subjects:	Natural sciences and mathematics Agriculture
Uncontrolled Keywords:	Keywords Language Adaptive potential English Natural variation English Sulfur content English
Date of oral exam:	15 June 2026
Referee:	Name Academic Title Kopriva, Stanislav Prof. Dr. Hildebrandt, Tatjana Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/80517