Microbe-associated molecular patterns (MAMPs) are molecular signatures typical of whole classes of microbes, and their recognition plays a key role in innate immunity. Endogenous elicitors are similarly recognized as damage-associated molecular patterns (DAMPs). This review focuses on the diversity of MAMPs/DAMPs and on progress to identify the corresponding pattern recognition receptors (PRRs) in plants. The two best-characterized MAMP/PRR pairs, flagellin/FLS2 and EF-Tu/EFR, are discussed in detail and put into a phylogenetic perspective. Both FLS2 and EFR are leucine-rich repeat receptor kinases (LRR-RKs). Upon treatment with flagellin, FLS2 forms a heteromeric complex with BAK1, an LRR-RK that also acts as coreceptor for the brassinolide receptor BRI1. The importance of MAMP/PRR signaling for plant immunity is highlighted by the finding that plant pathogens use effectors to inhibit PRR complexes or downstream signaling events. Current evidence indicates that MAMPs, DAMPs, and effectors are all perceived as danger signals and induce a stereotypic defense response.

A Renaissance of Elicitors: Perception of Microbe-Associated Molecular Patterns and Danger Signals by Pattern-Recognition Receptors

Plant hormones have pivotal roles in the regulation of plant growth, development, and reproduction. Additionally, they emerged as cellular signal molecules with key functions in the regulation of immune responses to microbial pathogens, insect herbivores, and beneficial microbes. Their signaling pathways are interconnected in a complex network, which provides plants with an enormous regulatory potential to rapidly adapt to their biotic environment and to utilize their limited resources for growth and survival in a cost-efficient manner. Plants activate their immune system to counteract attack by pathogens or herbivorous insects. Intriguingly, successful plant enemies evolved ingenious mechanisms to rewire the plant’s hormone signaling circuitry to suppress or evade host immunity. Evidence is emerging that beneficial root-inhabiting microbes also hijack the hormone-regulated immune signaling network to establish a prolonged mutualistic association, highlighting the central role of plant hormones in the regulation of plant growth and survival.

/pdf/hormonal-modulation-of-plant-immunity-na0dumzzdp.pdf

Hormonal Modulation of Plant Immunity

Jasmonates: biosynthesis, perception, signal transduction and action in plant stress response, growth and development. An update to the 2007 review in Annals of Botany

Elicitor signal transduction leading to production of plant secondary metabolites.

Infection of plants by necrotizing pathogens or colonization of plant roots with certain beneficial microbes causes the induction of a unique physiological state called "priming." The primed state can also be induced by treatment of plants with various natural and synthetic compounds. Primed plants display either faster, stronger, or both activation of the various cellular defense responses that are induced following attack by either pathogens or insects or in response to abiotic stress. Although the phenomenon has been known for decades, most progress in our understanding of priming has been made over the past few years. Here, we summarize the current knowledge of priming in various induced-resistance phenomena in plants.

/pdf/priming-getting-ready-for-battle-3b7z2rs6lg.pdf

Priming: Getting Ready for Battle

Arabidopsis thaliana nicotianamine synthase 4 is required for proper response to iron deficiency and to cadmium exposure.

https://hal.archives-ouvertes.fr/hal-01696272/document

Editorial: Plant Responses to Biotic and Abiotic Stresses: Lessons from Cell Signaling.

Anion effluxes are amongst the earliest reactions of plant cells to elicitors of defence responses. However, their properties and their role in disease resistance remain almost unknown. We previously demonstrated that cryptogein, an elicitor of tobacco defence responses, induces a nitrate (NO3−) efflux. This efflux is an early prerequisite to the cryptogein-triggered hypersensitive response (HR). Here, we analyzed the electrophysiological properties of the elicitor-mediated NO3−− efflux and clarified the mechanisms through which it contributes to cell death. Application of the discontinuous single electrode voltage-clamp technique in tobacco cells elicited with cryptogein enabled us to record the activation of slow-type deactivating anion channel currents. Cryptogein-induced plasma membrane depolarization and Ca2+ influx, an essential component of elicitor signalling for HR cell death, were prevented by inhibiting the NO3−− efflux. Similarly, pharmacological blocking of the anion efflux suppressed vacuola...

https://www.tandfonline.com/doi/pdf/10.4161/psb.2.2.4015

Cryptogein-induced anion effluxes: electrophysiological properties and analysis of the mechanisms through which they contribute to the elicitor-triggered cell death.

Mechanisms of Defence to Pathogens: Biochemistry and Physiology

Over the past two decades, it has been recognized that nitric oxide (NO) plays an important role in diverse mammalian physiological processes NO regulates physiological processes by modulating the activity of proteins principally by nitrosylation, a process referring to the binding of NO to a transition metal centre or cysteine residues [1] An important class of proteins that constitutes key targets of NO is that of the Ca2+ channels including plasma membranes as well intracellular Ca2+ channels NO modulates these channels directly by nitrosylation, but also indirectly via the second messenger cyclic GMP (cGMP) and/or cyclic ADP ribose (cADPR) Therefore, NO emerges as a key messenger governing the overall control of Ca2+ homeostasis [2]

In the late 1990s, NO also became an increasingly popular target for investigation in plants As in mammals, NO fulfils a broad spectrum of signaling functions in (patho)physiological processes in plants [3] Here, we summarise studies published in recent years that provide novel insights into the signaling functions of NO produced by plant cells exposed to abiotic stresses and biotic stress (pathogen-derived elicitors) It focuses particularly on the cross-talk operating between NO and Ca2+

/pdf/no-signaling-functions-in-the-biotic-and-abiotic-stress-3eolvus4rd.pdf

Olivier Lamotte

Papers

Arabidopsis thaliana nicotianamine synthase 4 is required for proper response to iron deficiency and to cadmium exposure.

Editorial: Plant Responses to Biotic and Abiotic Stresses: Lessons from Cell Signaling.

Cryptogein-induced anion effluxes: electrophysiological properties and analysis of the mechanisms through which they contribute to the elicitor-triggered cell death.

Mechanisms of Defence to Pathogens: Biochemistry and Physiology

NO signaling functions in the biotic and abiotic stress responses