Innate Immunity in Plants

In an environment that is rich in harmful microbes, the survival of higher eukaryotic organisms depends on efficient pathogen sensing and rapidly mounted defence responses. Such protective mechanisms are found in all multicellular organisms and are collectively referred to as innate immunity. General elicitors, or microbe‐associated molecular patterns (MAMPs), are conserved structures typical of whole classes of microbes that are sensed by a broad spectrum of host species. Recognition of MAMPs in both insects and mammals are often mediated by Leucine Rich Repeat (LRR) proteins such as Toll in Drosophila and the Toll‐like receptors (TLRs) in mammals. Remarkable similarities have been found between the MAMP perception in plants and animals.

Plants respond to MAMPs with induction of defence responses such as the oxidative burst, nitric oxide generation, cell-wall alterations and pathogenesis-related (PR) protein accumulation, leading to basal or non-host resistance, or MAMP triggered innate immunity. MAMPs perceived by plants include structures characteristic for oomycetes like the cell-wall β-glycan, the pep13 epitope conserved in cell-wall transglutaminases and secreted lipotransfer proteins termed elicitin. Plants also recognize structures made by true fungi like the cell-wall polysaccharide chitin and the fungal sterol ergosterol.  MAMPs from bacteria include cold-shock protein (CSP), flagellin, the elongation factor Tu (EF-Tu), lipopolysaccharides (LPS) and peptidoglycan (PGN)

 

 

Figure1. Known animal and plant receptors involved in recognition of bacterial MAMPs and other elicitors/effectors.

 

There are still many unanswered questions as to how surface receptors are connected to signaling molecules and how signaling events eventually are translated into changes in gene expression in the host.

 

There are several MSc and BSc projects within the area of innate immunity in plants.