Theses 2025–2026

Theses defended in late 2025 or early 2026

Michel HEIDECKER

Long non-coding RNAs in the regulation of alternative splicing

Keywords: Long non-coding RNAs, alternative splicing regulation, protein-RNA interaction

To regulate developmental processes, plants dynamically change their transcriptome, including alternative splicing (AS) of mRNAs and long non-coding RNAs (lncRNAs) expression. We used a bioinformatic and transient expression screen in the model plant Arabidopsis thaliana to identify lncRNAs that regulate AS. We characterized one lncRNA named ACHLYS, which is involved in root development. ACHLYS directly interacts with the splicing factor NSRa, which binding is also enriched in ACHLYS dependent AS events. High ACHLYS levels increase NSRa concentrations in nuclear speckles, a biomolecular condensate involved in splicing. This work contributed to further establish that AS regulates eukaryotic development and that lncRNAs are common regulators of AS regulatory networks.

PhD defense date: October 6, 2025

PhD co-supervisors: M. Crespi and J. Bazin

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Azhin MORTEZAZADEH

The role of photorespiration in stomatal movements of Arabidopsis thaliana

Keywords: Photorespiration, Stomata, Guard cells, Mesophyll cells, Gas exchange, Carbon assimilation, Water use efficiency, Crop improvement

During my thesis, I investigated the impact of the photorespiratory cycle activity on light-dependent stomatal opening, with a particular focus on the cell-type-specific nature of this phenomenon between guard cells and mesophyll cells. While stomata have long been recognized as key players in the trade-off between CO₂ uptake and water loss, the control of stomatal pore size has traditionally been attributed to complex signalling networks responding to environmental cues including water vapour pressure, light, temperature, and CO₂. A major conclusion of my thesis was that photorespiration, once considered a costly metabolic pathway arising from the oxygenase activity of Rubisco, is perhaps a metabolic hub influencing stomatal movements by modulating signalling networks and / or the plant metabolism involved in the production of osmolytes and ATP.

PhD defense date: December 9, 2025

PhD co-supervisor: M. Jossier

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Tao CHEN

Functional analyses of interaction between salicylic acid and thioredoxin m1 in Arabidopsis thaliana

Key words: Thioredoxin, salicylic acid, redox regulation, plant immunity

Salicylic acid (SA) is a key plant hormone regulating immunity and growth. The chloroplast thioredoxin m1 (TRX m1) was previously identified as an SA-binding protein, yet its functional significance remained unexplored. My PhD work investigated the mechanism underlying this interaction and its role. Biochemical analyses with purified recombinant proteins reveal that SA inhibits both TRX m1 reduction and its regulatory activity toward target enzymes. Active site residue Lys41 proved essential for SA binding and these effects. Furthermore, SA quantification and expression profiling of ROS- and SA-related genes in Arabidopsis suggest that the TRX m plays a critical role in modulating photoperiod-dependent defence responses driven by intracellular oxidative stress.

PhD defense date: January 28, 2026

PhD co-supervisors: E. Issakidis-Bourguet and G. Noctor

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24/07/2026