The chloroplast plays a central role in facilitating MAMP-Triggered
Immunity, pathogen suppression of immunity and crosstalk with abiotic
stress.
Abstract
Microbe associated molecular pattern (MAMP) triggered immunity research
has traditionally centred around signal transduction pathways
originating from activated membrane localised pattern recognition
receptors (PRRs), culminating in nuclear transcription and post
translational modifications. More recently, chloroplasts have emerged as
key immune signalling hubs. Chloroplasts play a central role in
integrating environmental signals. Notably MAMP recognition induces
chloroplastic ROS (cROS) which is suppressed by pathogens effectors,
which also modify the balance of defence hormone precursors, jasmonic
acid (JA), salicylic acid (SA) and abscisic acid (ABA), whose precursors
are chloroplast synthesised. This study focuses on how well
characterised PRRs and co-receptors modulate chloroplast physiology,
examining whether diverse signalling pathways converge to similarly
modulate chloroplast function. Pre-treatment of receptor mutant plants
with MAMP and D(Damage)AMP peptides usually protect against effector
modulation of chlorophyll fluorescence and prevent Pseudomonas
syringae effector mediated quenching of cROS and suppression of
Fv/Fm. The MAMP-triggered
immunity (MTI) co-receptor double mutant, bak1-5/bkk1-1, exhibits
a remarkable decrease in Fv/Fm
compared to control plants during infection, underlining the importance
of MTI mediated signalling in chloroplast immunity. Further probing the
role of the chloroplast in immunity we unexpectedly found that high
light uncouples plant immune signalling.