Plant MAMPs

In this chapter, we will review the current knowledge of the role of LPS as a M AMP in plant innate immunity. We will give an overview of the range of responses induced by LPS, the sub-structures within LPS that are recognized by plants and variations within the LPS structure that can alter its activity as a MAMP. We will go on to discuss new work that suggests a role for the plasma-membrane resident syntaxin PEN1 in transduction of the LPS signal. 

The body of work outlined above demonstrates conclusively that LPS from diverse bacteria can act as a MAMP to either directly induce a range of plant defense responses or prime induction of those responses in both a local and systemic fashion. Differences between the activities of LPS in different plants are however seen. These may relate in part to the plant experimental systems used, the isolation procedures and purity of LPS preparations and to differences in LPS structure. For example global transcriptional profiling of Arabidopsis cells treated with Burkholderia cepacia LPS revealed, surprisingly, that very few PR transcripts... 

Structural analysis of LOS from a mutant of Xcc defective in core completion revealed that this mutant had modifications in the lipid A moiety, which had reduced acylation and was further derivatised with phosphoryl ethanolamine residues (Dow et al., 1995 Silipo et al., 2008). These changes in lipid A structure abolished the ability to trigger innate immune responses in Arabidopsis (Silipo et al., 2008). Importantly these findings indicate that Xcc has the capacity to modify the structure of its lipid A to reduce its activity as a MAMP in plants (Silipo et al., 2008). It is not known whether these (or other) modifications to lipid A occur when bacteria are within plants. 

Bittel P, Robatzek S (2007) Miciobe-assoeiated moleeular patterns (MAMPs) probe plant immunity. Curr Opin Plant Biol 10 335-341... 

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