Lea-Franziska Reekers (Münster University)
Lea-Franziska Reekers's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Westfälische Wilhelms-University Münster in the year 2021.
Title: A detailed localization analysis of the enzymes involved in Lewis a-epitope formation in Arabidopsis thaliana
The study shows a way to visualize the full-length version of Arabidopsis Galactosyltransferase 1 (GalT1) for the first time, which – besides studying its own localization – also allowed to investigate a possible interaction with the follow-up enzyme Fucosytransferase c (FucTc).
N-glycans are attached co-translationally to nascent glycoproteins in the ER lumen (Abeijon & Hirschberg, 1992; Helenius & Aebi, 2002), and become further modified during travelling through the Golgi apparatus (Faye et al., 1989). The last modifications in plant cells are synthesized by the membrane-anchored enzymes GalT1 and FucTc, which results in complex-type N-glycans with terminal Lewis-a epitopes (Fitchette-Laine et al., 1997; Leonard et al., 2002). These epitopes on plant secretory glycoproteins were immunologically detected only at the TGN and the plasma membrane/cell wall. However, Arabidopsis FucTc localized as C-terminal reporter fusion not only in the Golgi apparatus, but preferentially at the perinuclear ER (Rips et al., 2017).
In my thesis I have investigated a possible cause for this phenomenon by analyzing multiple reporter fusions via CLSM microscopy upon transient expression in protoplasts. The protoplasts were either prepared from A. thaliana wildtype or knock-out mutants that I had obtained by the CRISPR/Cas9 system for the FUCTc and GALT1 genes. Thereby I could show that GalT1 (Strasser et al. 2007), which could not be visualized as full-length version so far, is a factor involved in releasing FucTc from the perinuclear ER to the Golgi. Moreover, also FucTc seems to influence the localization of GalT1, which further supports an interaction of the two enzymes in the secretory system. My work has therefore contributed to solving a puzzle in plant cell biology.
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Lea-Franziska Reekers conducted this work at the Institute of Plant Biology & Biotechnology (IBBP, WWU Münster) in the group of Prof. Dr. Antje von Schaewen.
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Referenzen
Abeijon, C., & Hirschberg, C. B. (1992). Topography of glycosylation reactions in the endoplasmic reticulum. Trends in Biochemical Sciences, 17(1), 32–36. doi.org/10.1016/0968-0004(92)90424-8
Faye, L., Johnson, K. D., Sturm, A., & Chrispeels, M. J. (1989). Structure, biosynthesis, and function of asparagine‐linked glycans on plant glycoproteins. Physiologia Plantarum, 75(2), 309–314. doi.org/10.1111/j.1399-3054.1989.tb06187.x
Fitchette-Laine, A.-C., Gomord, V., Cabanes, M., Michalski, J.-C., Saint Macary, M., Foucher, B., Cavelier, B., Hawes, C., Lerouge, P., & Faye, L. (1997). N-glycans harboring the Lewis a epitope are expressed at the surface of plant cells. The Plant Journal, 12(6), 1411–1417. doi.org/10.1046/j.1365-313x.1997.12061411.x
Helenius, J., & Aebi, M. (2002). Transmembrane movement of dolichol linked carbohydrates during N-glycoprotein biosynthesis in the endoplasmic reticulum. Seminars in Cell and Developmental Biology, 13(3), 171–178. doi.org/10.1016/S1084-9521(02)00045-9
Leonard, R., Costa, G., Darrambide, E., Lhernould, S., Fleurat-Lessard, P., Carlue, M., Gomord, V., Faye, L., & Maftah, A. (2002). The presence of Lewis a epitopes in Arabidopsis thaliana glycoconjugates depends on an active 4-fucosyltransferase gene. Glycobiology, 12(5), 299–306. doi.org/10.1093/glycob/12.5.299
Rips, S., Frank, M., Elting, A., Offenborn, J. N., & von Schaewen, A. (2017). Golgi α1,4-fucosyltransferase of Arabidopsis thaliana partially localizes at the nuclear envelope. Traffic, 18(10), 646–657. doi.org/10.1111/tra.12506
Strasser, R., Bondili, J. S., Vavra, U., Schoberer, J., Svoboda, B., Glössl, J., Léonard, R., Stadlmann, J., Altmann, F., Steinkellner, H., & Mach, L. (2007). A unique β1,3-galactosyltransferase is indispensable for the biosynthesis of N-glycans containing Lewis a structures in Arabidopsis thaliana. Plant Cell, 19(7), 2278–2292. doi.org/10.1105/tpc.107.052985