Plant Innate Immunity 2020

Dear Colleagues,

Plants are sessile organisms that are under constant attack from microbes. They rely on both preformed defences and their innate immune system to ward off pathogens. Preformed defences include, for example, the cell wall, which acts as a physical barrier to microbial invasion. The plant’s induced immune system is composed of a two-branched surveillance system, where the first branch is a relatively fast acting system comprising several general microbe elicitors, which allows plants to switch from growth and development into defence mode, thus rejecting most potentially harmful microbes. The general microbe elicitors, also called microbe-associated molecular patterns (MAMPs), are recognized via plasma membrane localized pattern recognition receptors (PRRs), and they lead to pattern-triggered immunity (PTI). MAMPs are essential structures for microbe survival and are conserved among microbes. General elicitors like flagellin (Flg), elongation factor Tu (EF-Tu), peptidoglycan (PGN), lipopolysaccharides (LPS), and Ax21 (Activator of XA21-mediated immunity in rice) from bacteria, fungal chitin, and β-glucans from oomycetes are recognized by plant surface localized PRRs. However, pathogens and other microbes (such as endophytes) have developed specialized effectors, which interfere with PTI, causing effector-triggered susceptibility (ETS), where the pathogen proliferates in the plant and causes full blown disease. As a consequence of this selection pressure, some plants have developed resistance (R) genes that encode for intracellular receptors that recognize these effectors, either directly or indirectly. This leads to the second branch of plant immunity, effector-triggered immunity (ETI), and full resistance. This response is typically faster and stronger than PTI and often includes the hypersensitive response (HR).

This Special Issue focuses on the current knowledge on important MAMPs from bacteria, fungi, and oomycetes, their structures, the plant PRRs that recognize them, and how they induce MAMP-triggered immunity (MTI or PTI) in plants. Until recently, the focus on plant–microbe interactions has been reaction, namely defence responses to pathogenic organisms. More recent research has focused on mutual signalling in symbiotic and neutral interactions, for instance, mycorrhizal and endophytic fungi, and these will also be included here.

Dr. Mari-Anne Newman
Prof. Dr. David B. Collinge
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• plant immunity
• Arabidopsis thaliana
• Hordeum vulgare
• Xanthomonas campestris
• Pseudomonas syringae
• Fusarium head blight
• Blumeria graminis
• Fusarium graminearum
• endophytic fungi
• zig-zag model
• pattern-triggered immunity (PTI) or MAMP-triggered immunity (MTI)
• effector-triggered susceptibility (ETS)
• effector-triggered immunity (ETI)
• microbe-associated molecular patterns (MAMPs)
• lipopolysaccharide (LPS)
• peptidoglycan (PGN)
• pattern recognition receptors (PRRs)
• bacterial and fungal effectors
• receptor-like protein kinases
• NAC transcription factors
• mechanisms of biological control