Innate immunity in plants and animals: striking similarities and obvious differences

Abstract

Innate immunity constitutes the first line of defense against attempted microbial invasion, and it is a well-described phenomenon in vertebrates and insects. Recent pioneering work has revealed striking similarities between the molecular organization of animal and plant systems for nonself recognition and anti-microbial defense. Like animals, plants have acquired the ability to recognize invariant pathogen-associated molecular patterns (PAMPs) that are characteristic of microbial organisms but which are not found in potential host plants. Such structures, also termed general elicitors of plant defense, are often indispensable for the microbial lifestyle and, upon receptor-mediated perception, inevitably betray the invader to the plant's surveillance system. Remarkable similarities have been uncovered in the molecular mode of PAMP perception in animals and plants, including the discovery of plant receptors resembling mammalian Toll-like receptors or cytoplasmic nucleotide-binding oligomerization domain leucine-rich repeat proteins. Moreover, molecular building blocks of PAMP-induced signaling cascades leading to the transcriptional activation of immune response genes are shared among the two kingdoms. In particular, nitric oxide as well as mitogen-activated protein kinase cascades have been implicated in triggering innate immune responses, part of which is the production of antimicrobial compounds. In addition to PAMP-mediated pathogen defense, disease resistance programs are often initiated upon plant-cultivar-specific recognition of microbial race-specific virulence factors, a recognition specificity that is not known from animals.

Ubiquitination-mediated protein degradation and modification: an emerging theme in plant-microbe interactions

“…Such pathogen recognition and subsequent induction of defense responses is critical to the protection of plants if preformed barriers are overcome by an evolutionarily active population of pathogens, which is frequently the case in nature. Based on whether the attacked plants are natural hosts of the pathogen or not, resistance to pathogens can be divided at 'species' and 'cultivar' levels, respectively [3]. The species-level resistance, also known as non-host resistance, refers to the fact that any given pathogen can only cause disease on a limited range of plant species.…”

The Fractionated Orthology of Bs2 and Rx/Gpa2 Supports Shared Synteny of Disease Resistance in the Solanaceae

“…Comparative studies of sequence similarity between plant R proteins and proteins of innate immunity in animals have made important contributions toward understanding R-protein structure, the role of individual protein domains, and the mechanism by which R proteins identify and respond to foreign proteins (Nurnberger et al 2004;Takken et al 2006;Rairdan and Moffett 2007). Both share a central nucleotidebinding (NB) site and a region of homology termed the ''ARC'' domain (collectively referred to as the NB-ARC) (van der Biezen and Jones 1998; Rairdan and Moffett 2007).…”

Mucosal immunity: aliment and ailments

“…Innate immunity is the main anti-microbial defense mechanism in plants and invertebrates, and is triggered by various microbial ligands that are recognized in the host by pattern recognition receptors (PRRs). 5 Th e signature eff ector molecules of this defense system in invertebrates are antimicrobial molecules such as lysozyme, complement factors, lectins, and antimicrobial peptides. In contrast to innate immunity, adaptive immunity evolved only in vertebrates and functions as an important part of their defense system.…”