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Investigating the role of the Wall Associated Kinase Like 7 in sensing the activity of the Pectin Methyl Esterase 17

ABG-99826 Master internship 6 months 587 EUR
2021-09-02
IJPB INRAE Versailles
Versailles Ile-de-France France
  • Biology
  • Biochemistry

Employer organisation

The ‘Institut Jean-Pierre Bourgin’ is one of the largest research centers in Plant Sciences in Europe. It gathers a unique ensemble of experimental resources and pluridisciplinary expertise in biology, chemistry and mathematics. The IJPB is a joint research unit under the supervision of INRAE and AgroParisTech, consequently belonging to University Paris-Saclay. IJPB is also a founding member of the EUR Saclay Plant Sciences (SPS).

The Jean-Pierre Bourgin Institute explores multidisciplinary concepts and tools, in order to develop new approaches in plant biology and agronomy, and face new questions from the society.

Dedicated from its origins to research in agronomy and plant biology, following a long local tradition predating INRA, the Versailles INRAE Research Centre hosts the Jean-Pierre Bourgin Institute (IJPB). The laboratories that predate IJPB have pioneered several research fields. Georges Morel and his students made several important discoveries in plant cell biology (meristem culture) and pathology (Agrobacterium). Thereafter, Jean-Pierre Bourgin, whose seminal research on haploidization in plants had a tremendous impact in the field, headed this laboratory, with dedication, for several years. He notably favoured the emergence of molecular genetics, genomics and the use of model species like Arabidopsis in plant biology, together with scientists like Yves Chupeau, Michel Caboche, Georges Pelletier, Alain Deshayes, Francine Casse-Delbart and many others since then... In a working climate based on trust, solidarity and respect, they have shaped a world-renowned institute in plant cell and molecular genetics. 

Description

Pectocellulosic cell walls surround every plant cell. They provide a structural framework to support environmental constraints and act as the first line of defense against pathogens. They are made up of cellulose organized as individual microfibrils that interacts with matrix polysaccharides: the hemicelluloses and pectins. Pectins are highly enriched in galacturonic acid residues and three main blocks can be distinguished: the rhamnogalacturonan I, the rhamnogalacturonan II and the homogalacturonans (HGs). The latter are the most abundant pectic polysaccharides. They are highly dynamic polymers of 1,4-α-linked GalA synthesized in a highly methylesterified form in the Golgi apparatus. HGs are next partially de‐methylesterified in muro by pectin methylesterases (PMEs). This HG demethylesterification plays a key role in the control of cell wall rheology underlying plant growth but also exposes the polymer to degradation by pectinases.

Among the 66 PMEs expressed in Arabidopsis thaliana, we focused our research AtPME17 which is highly induced on upon Botrytis cinerea-Arabidopsis thaliana interaction and senescence, two physiological processes that activate plant defense and lead to cell death. We worked on mutants generated in Wassilewskija and Colombia ecotypes (Ws-pme17 and Col-pme17). We first investigated the effect of PME17 activity on pectin structure in planta and observed that this PME promotes homogalacturonan and more surprisingly xylogalacturonan demethylesterification. Xylogalacturonan is made up of a homogalacturonan backbone substituted by xylosyl residues. Although the role of this polymer has been poorly investigated, it is likely involved in cell detachment. We next investigated the role of PME17 in plant defense and observed that Ws-pme17 was highly resistant to B. cinerea and Colletotrichum higginsianum, and displays late senescence in comparison with the Ws parental ecotype and the Col-pme17 mutants. Ws-pme17 mutants also accumulate very specific oligosaccharides compared to Ws and Col-pme17.

In order to better understand these ecotype-dependent differences, we performed a transcriptomic analysis which revealed WALL ASSOCIATED KINASE LIKE 7 (WAKL7), encoding a putative pectin receptor, was overexpressed in Ws-pme17 compared to Ws and that Col-WAKL7 encodes a truncated WAK-like kinase compared to Ws-WAKL7. We therefore investigated the role of Ws-WAKL7 in plant physiology. We observed that Ws-wakl7, similarly to Ws-pme17, is resistant to B. cinerea and displays a late senescence. At the molecular level, we also observed that Ws-walk7 and Ws-pme17 accumulate similar endogenous oligosaccharides although wakl7 does not display any cell wall defects. The student recruted will investigate the role of Ws-WAKL7 in sensing the cell wall integrity in presence or absence of PME17 as well as the WAKL7-dependant signaling cascade. 

METHODOLOGIES :

Phenotypic characterization of Col-pme17 mutants and Col- PME17 overexpressor lines that express Ws-WAKL7.

Characterization of oligosaccharides produced by these different lines by mass spectrometry

WAKL7 pull down experiment.

Analysis of the transcriptomic data generated from wakl7 mutant

REFERENCES

Voxeur, A.; Habrylo, O.; Guénin, S.; Miart, F.; Soulié, M.-C.; Rihouey, C.; Pau-Roblot, C.; Domon, J.-M.; Gutierrez, L.; Pelloux, J.; Mouille, G.; Fagard, M.; Höfte, H.; Vernhettes, S. Oligogalacturonide Production upon Arabidopsis thaliana/Botrytis cinerea Interaction. Proc Natl Acad Sci USA 2019, 116 (39), 19743. 

Voxeur, A.; Séchet, J.; Vernhettes, S. Plant Inositol-Phosphate-Glycans and Fucosylated Xyloglucan Oligosaccharide Are Accumulated upon Arabidopsis Thaliana/ Botrytis Cinerea Infection; preprint; Plant Biology, 2021.

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Master 2 student in Plant Sciences

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