N-Glycosylation mediation of Plant Immunity in Arabidopsis

Matt Borchardt and Jessica Allen

Max-Planck Society for the Advancement of Science

• Originally created as the Kaiser Wilhelm Society in 1911, changed in 1948

• Boasts 32 Nobel Prizes awarded to their scientists• Top Non-University Institution in Science by Times

Higher Education• Albert Einstein, Fritz Haber, and Peter Debye were

named directors at some point in its history

http://en.wikipedia.org/wiki/Max-Planck-Gesellschaft

• Arabidopsis– Brassicaceae family– model organism• ABC Plant Model

– First plant to have entire genome sequenced

http://en.wikipedia.org/wiki/Arabidopsis

Signaling in Cells

• Cells are constantly being introduced to various signals inside and outside of the cell– Signal receptors are signal-specific– Causes a cellular response

Example of Cell Signaling

219.221.200.61/ywwy/zbsw(E)/edetail6.htm

Cell Signaling and Plants

• Cell signaling is important for Plant Immunity• Provides feedback systems to promote

cellular defense– Growth inhibition– Production of Reactive Oxygen Species (ROS)• “oxidative burst”

– Apoptosis

Plant Receptors

• Pattern Recognition Receptors (PRRs)– membrane-bound protein of the innate immune

system– recognize microbe-associated molecular patterns

(MAMPs) on pathogens– Contain membrane-bound polysaccharides

• Arabidopsis has approximately 56 known RLPs– EFR recognizes and responds to elf18– FLS2 recognizes and responds to flg22

• MAMPs are recognized by N-glycans on PRRs

• N-Glycans– Attach to asparagine residues of

plasma membrane– Initial contact between plant cells

and pathogens

N-glycosylation

• Occurs in eukaryotes during/after translation• Linking of 14-sugar precursor to the

asparagine in the polypeptide chain

12-52.Molecular Biology of the Cell, 4th Edition

Oligosaccharyltransferase Complex

• Transfers the 14-sugar oligosaccharide from dolichol to the protein

• The central step in N-linked glycosylation• Located in the ER• Post-translational modification

http://www.ier.tokushima-u.ac.jp/bunshi-seiri/physiol/images/PfSTT3.jpg

N-Glycosylation Intermediates

Altered/Prevention of N-Glycosylation

• Creates unfolding of proteins • Only correctly folded proteins are exported

from the ER• Causes a reduction in receptor accumulation– Causes lack of receptor-signal induced pathways– Leads to decreased immune response

In this study

– Mutated genes produce plants with modifications in the N-glycosylation steps• stt3a

• Genes present in ER which encode for oligosaccharyltransferase complex

Tunicamycin

- Antibiotic- Blocks glycoprotein synthesis in first step of

glycosylation- Causes arrest of cell cycle in G1- Produced by bacterium Streptomyces

http://fermentek.co.il/tunicamycin.htm

PRR-EFR

PRR-FLS2Plasma Membrane

Golgi Apparatus

Endoplasmic Reticulum

Seedling GrowthROS

BacteriaMAMP

BacteriaMAMP