Universität zu Köln

López Ramos, José María (2023). Dissection of the signalling function of O-acetylserine in plants. PhD thesis, Universität zu Köln.

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Abstract

Sulfur is an essential element for plant growth, development, defense and many other physiological processes. It is taken up by the roots, reduced and incorporated into organic compounds. Sulfate assimilation is well described in plants, however the regulation and sensing are not yet fully understood. O-acetylserine (OAS) is the acceptor of the reduced sulfur and the precursor of cysteine. OAS has been extensively discussed as a signalling molecule in sulfur metabolism, as it accumulates during sulfur starvation and induces the expression of sulfur marker genes. A systems biology approach established a group of 6 genes whose expression correlated to OAS accumulation, the so-called OAS cluster genes. In this study, we recreated the experimental set-up that led to the discovery of the cluster in combination with gene expression and metabolite analyses with different Arabidopsis thaliana mutants in order to identify the mechanisms leading to OAS accumulation and dissect the regulation of the OAS cluster genes. Our study revealed that every SERAT isoform can contribute to the induction of the OAS cluster genes, with SERAT2;2 taking up a major role. Moreover, our deficiency experiments point towards OAS as a long term signal adjusting and coordinating the carbon, nitrogen and sulfur pathways. Regarding the OAS cluster genes, we identified SLIM1 (key transcription factor in sulfur deficiency response), RVE1 and RVE8 (circadian clock related transcription factors) as essential elements for their transcriptional activation. The 3 transcription factors were found to be involved in the control of OAS accumulation as well. Their binding to the promoters of the OAS cluster genes was confirmed and their role was tested in different conditions. SLIM1 emerged as the main regulator of the cluster, with RVE1 and RVE8 taking a more context-dependent function. Furthermore, our study directly and indirectly established new connections between the circadian clock and sulfur metabolism. We confirmed the circadian expression pattern of the OAS cluster genes and their transcriptional regulation by RVE1 and RVE8. We also demonstrated that the early sulfur deficiency response at different times of the day differs in its magnitude. Additionally, we provided new information about SLIM1, showing that it acts as a repressor of the OAS transcriptional signal and that it is not involved in the early response to sulfur starvation. These findings contribute to a better understanding of the regulation of sulfur homeostasis but also show that the regulation is more complex than initially believed.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code López Ramos, José María jmlopezramos18@gmail.com UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-721576
Date:	2023
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 Life sciences
Uncontrolled Keywords:	Keywords Language O-acetylserine English Sulfur deficiency English Arabidopsis English Circadian Clock English SLIM1 English OAS cluster English RVE1 English RVE8 English
Date of oral exam:	20 September 2023
Referee:	Name Academic Title Riemer, Jan Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/72157