Universität zu Köln

Günal, Süleyman ORCID: 0009-0005-3160-9374 (2025). Partitioning of sulfur between primary and secondary metabolism in Arabidopsis thaliana. PhD thesis, Universität zu Köln.

PDF Süleyman_Günal_Ph.D._Thesis_2025.pdf - Published Version Download (5MB)

Abstract

Sulfur is a fundemental element for all living organisms. It is essential for plant development and defense against biotic and abiotic stresses. The partitioning of sulfur between primary and secondary sulfur metabolism is controlled with delicate balance in Arabidopsis thaliana. An increased drought endurance of secondary sulfur metabolism mutants gave rise to a question about the importance of the distribution of sulfur metabolites under stress. Decreasing the secondary sulfur metabolism caused accumulation of primary sulfur metabolites cysteine and glutathione. The secondary sulfur mutant apk1apk2 (APS kinase) possessed an enhanced primary sulfur reservoir. This observation and crosses we created in the sulfur metabolism gave us a great opportunity to investigate role of sulfur compounds under stress conditions. To understand underlying mechanism better we crossed apk1apk2 mutant with previously well characterized Arabidopsis mutants from primary sulfur metabolism, apr2 (APS reductase), cad2 (γ-glutamylcysteine synthetase), and des1 (L-cysteine desulfhydrase). The apk1apk2apr2, apk1apk2cad2 triple mutants, as well as cad2apr2 and cad2des1 double mutants were analyzed for alterations in key processes of sulfur metabolism. We observed increased drought tolerance and ability to contain photosynthetic efficiency in GSH accumulating mutants and decrease of stomata density and enhanced water retention abilities in cysteine accumulating mutants. We also showed higher concentrations of cysteine alone is not sufficient for drought endurance, cysteine degradation is also needed for the resistance mechanism. The mutants with alternating sulfur metabolite profiles gave us a comparative advantage for understanding the different roles of cysteine and glutathione. For the second part of this thesis we investigated the role of PAP in mitochondria. PAP is a phosphorylated nucleotide which is well characterized as a retrograde signaling molecule from chloroplasts to nucleus. In plants SAL1 enzyme recycles PAP. However, neither the connections between metabolic reactions producing PAP in mitochondria as a by-product nor the role of PAP as a counter-transport molecule of Coenzyme A or its inhibitory effect on mitochondrial iron transport have been investigated in plants yet. PAP is formed primarily, after consumption of PAPS for sulfation of secondary sulfur metabolites in animals and plants. Effects of in vivo PAP accumulation to mtFAS, CoA transport into the mitochondria and downstream mtFe-S assembly are still open questions. We investigated the possible effect of PAP accumulation on lipolylation of GDC and lipolylated TCA cycle enzymes with metabolomics approach. We used loss of function mutant, fou8, of PAP degradation enzyme SAL1 which has PAP accumulation and as a contrasting genotype we used apk1apk2 double mutant which has decreased concentrations of PAP. We observed, strongly and oppositely affected TCA cycle intermediates for both mutants. Our findings and reanalysis of existing expression data open the way for possible and intriguing connection of PAP and mitochondria.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Günal, Süleyman suleymangunall@gmail.com orcid.org/0009-0005-3160-9374 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-784937
Date:	2025
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Biology > Botanical Institute
Subjects:	Life sciences
Uncontrolled Keywords:	Keywords Language Sulfur metabolism UNSPECIFIED Sulfation UNSPECIFIED Drought UNSPECIFIED APS Kinase UNSPECIFIED Cysteine accumulation UNSPECIFIED Glutathione UNSPECIFIED 3′-Phosphoadenosine 5′-phosphate(PAP) UNSPECIFIED Phosphopantetheinylation UNSPECIFIED mitochondrial fatty acid synthesis UNSPECIFIED TCA cycle UNSPECIFIED mitochondrial CoA transport UNSPECIFIED mitochondrial Fe-S assembly UNSPECIFIED
Date of oral exam:	2025
Referee:	Name Academic Title Kopriva, Stanislav Prof.Dr Hildebrandt, Tatjana Prof.Dr Schwarz, Günter Prof.Dr
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/78493