Chloroplasts play a central role in facilitating MAMP‐triggered immunity, pathogen suppression of immunity and crosstalk with abiotic stress. (5th August 2022)

• Record Type: Journal Article
• Authors: Breen, Susan; Hussain, Rana; Breeze, Emily; Brown, Hannah; Alzwiy, Ibrahim; Abdelsayed, Sara; Gaikwad, Trupti; Grant, Murray
• Is Part Of: Plant, cell and environment. Volume 45:Number 10(2022)
• Page Start: 3001
• Page End: 3017
• Publication Date: 2022-08-05
• Subjects: chlorophyll fluorescence -- chloroplast reactive oxygen -- pattern recognition receptors -- plant immunity; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.14408
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: Microbe‐associated molecular pattern (MAMP)‐triggered immunity (MTI) research has traditionally centred around signal transduction pathways originating from activated membrane‐localized pattern recognition receptors (PRRs), culminating in nuclear transcription and posttranslational modifications. More recently, chloroplasts have emerged as key immune signalling hubs, playing a central role in integrating environmental signals. Notably, MAMP recognition induces chloroplastic reactive oxygen species (cROS) that is suppressed by pathogen effectors, which also modify the balance of chloroplast‐synthesized precursors of the defence hormones, jasmonic acid, salicylic acid (SA) and abscisic acid. This study focuses on how well‐characterized PRRs and coreceptors modulate chloroplast physiology, examining whether diverse signalling pathways converge to similarly modulate chloroplast function. Pretreatment 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 maximum dark‐adapted quantum efficiency (the ratio of variable/maximum fluorescence [ F v / F m ]). The MTI coreceptor double mutant, bak1‐5/bkk1‐1, exhibits a remarkable decrease in F v / F m 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 even moderate changes in light intensity can uncouple plant immune signalling.