Regulation and Contribution of

**Regulation and contribution of homogalacturonan-type pectin metabolism during the temperature-induced growth**:

- Réf **ABG-126659**
- Stage master 2 / Ingénieur- Durée 6 mois- Salaire net mensuel 567 euros- 05/11/2024- UMR INRAe BioEcoAgro 1158- Université de Picardie Jules Verne- Lieu de travail- Amiens Les Hauts de France France- Champs scientifiques- Biologie- 15/12/2024**Établissement recruteur**:
**Site web**:
**Research Team and context of the Master 2 project***
- The UMRT 1158 BioEcoAgro - BIOPI « Plant Biology and Innovation » research unit is based in Amiens (1h15 from Paris by train) and has access to all the equipment from the University platforms (Analytical, Microscopy, Molecular Biology, Greenhouses, Phenotyping robot), with state-of-the-art facilities. Our research team has notably a strong expertise in functional genomics approaches, gene expression (high-throughput qRT-PCR), biochemistry and analytical chemistry of cell wall metabolism. Over the recent years, the team has pioneered approaches to express pectin-modifying enzymes from plants in yeast heterologous system (_Pichia pastoris_), thus characterizing their structural/biochemical specificities and their role in plant development. The team has thus developed a strong expertise in protein expression, production and purification.- The research team has recently obtained an ANR funding for the next 4 years, with the CROSSING project, aiming to investigate cross-talk between HG metabolism and hormonal signaling under the TIHE. Interestingly, the hired Master 2 trainee will have the opportunity to continue, after its internship, on a similar research topic, since a PhD contract is funded in CROSSING and should start in October 2025.**Description**:
**State of the art***
- Plants growing under elevated temperature establish fast growth of selective organs, but this response unfortunately occurs at the expense of storage organs and plant defenses, thus reducing crop yields. In Arabidopsis seedlings, elevated temperature induces fast hypocotyl growth and this notably involves the Phytochrome Interacting Factors (PIFs), transcription factors that modulate the expression of genes regulating growth. In particular, PIFs modulate auxin and brassinosteroids synthesis, thus involving hormonal signaling in the regulation of growth promoting genes, during the temperature-induced hypocotyl elongation (TIHE). Interestingly, a large number of genes encoding cell wall-related genes, appear as modulated through PIFs, auxin and brassinosteroids pathways, suggesting that cell wall metabolism contributes to this growth response.- In plants such as _Arabidopsis thaliana_, growth is notably dependent of the primary cell wall, which has apparent contradictory roles with mechanical properties required to determine cell shape and plasticity/elasticity needed to allow cell expansion. The primary cell wall is composed of structural proteins and various polysaccharides, leading to a complex but however dynamic architecture that allows plant growth. Pectin, one of the main cell wall polysaccharides, is constituted by 4 domains rich in Galacturonic Acids (Gal-A) including HomoGalacturonan (HG), the most simple and abundant pectic polymer. HG corresponds to a linear backbone of Gal-A that is highly methylesterified by HG MethylTransferases (HGMTs) in Golgi apparatus, before its secretion into the cell wall, where it can be selectively demethylesterified by Pectin MethylEsterases (PMEs), themselves regulated by inhibitors (PMEIs). This regulation of the degree/pattern of methylesterification can lead to the production of various substrates for HG degrading enzymes, leading to HG depolymerization in OligoGalacturonides (OGs, HG fragments) and cell wall loosening. OGs can have signaling functions, as they can bind some cell wall integrity receptors located at the plasma membrane. Thus, changes in HG metabolism might be sensed, enabling signal transduction from cell wall to cell for modulating expression of genes related to growth, notably through hormonal pathways. **The regulation and contribution of the degree and pattern of methylesterification thus appear as essential for modulating OG signaling and ultimately growth, however this remains an open question.**

**Research Program***
- The Master 2 project aims to target this main question using the TIHE as developmental model, notably since this will bring new fundamental aspect in the growth regulation in the context of temperature rise and because growth response can be easily controlled in lab by transferring seedlings from moderated to high temperature. This project will be implemented through multidisciplinary approaches following two research axes.**The first axis will be dedicated to functionally investigate (i) the regulation of HG metabolism by hormonal pathways during the TIHE, and (ii) the contribution of HG metabolism in the TIHE.**
- For this purpose, the host lab has already identified mutants i