Cell wall integrity signaling and innate immunity in plants

Thomas S Nühse

doi:10.3389/fpls.2012.00280

Abstract

All plant pathogens and parasites have had to develop strategies to overcome cell walls in order to access the host’s cytoplasm. As a mechanically strong, multi-layered composite exoskeleton, the cell wall not only enables plants to grow tall but also protects them from such attacks. Many plant pathogens employ an arsenal of cell wall degrading enzymes, and it has long been thought that the detection of breaches in wall integrity contributes to the induction of defense. Cell wall fragments are danger-associated molecular patterns or DAMPs that can trigger defense signaling pathways comparable to microbial signals, but the picture is likely to be more complicated. A wide range of defects in cell wall biosynthesis leads to enhanced pathogen resistance. We are beginning to understand the essential role of cell wall integrity surveillance for plant growth, and the connection of processes like cell expansion, plasma membrane–cell wall contact and secondary wall biosynthesis with plant immunity is emerging.

Highlights

All plant pathogens and parasites have had to develop strategies to overcome cell walls in order to access the host’s cytoplasm
It is unclear how cell wall composition is controlled by these signaling proteins, but the positive correlation of increased uronic acid and decreased xylose with susceptibility to P. cucumerina has been confirmed in additional mutants (Sanchez-Rodriguez et al, 2009; Delgado-Cerezo et al, 2011)
Several of the powdery mildew resistant mutants may fall into this category (Vogel et al, 2002, 2004). Both pmr5, mapped to one member of a large plant-specific gene family related to TRICHOME BIREFRINGENT (Bischoff et al, 2010) and pmr6, a pectate lyase mutant, have increased levels of unesterified pectin and activate resistance via an unknown pathway that is independent of the well-studied salicylic acid (SA), ethylene (ET), or jasmonic acid (JA)-responsive paths

Summary

Introduction

All plant pathogens and parasites have had to develop strategies to overcome cell walls in order to access the host’s cytoplasm. It is unclear how cell wall composition is controlled by these signaling proteins, but the positive correlation of increased uronic acid and decreased xylose with susceptibility to P. cucumerina has been confirmed in additional mutants (Sanchez-Rodriguez et al, 2009; Delgado-Cerezo et al, 2011).

Results

Conclusion