title: Role of extracytoplasmic leucine rich repeat proteins in plant defence mechanisms.
abstract: Plant-pathogen interactions involve highly complex series of reactions in disease development. Plants are endowed with both, resistance and defence genes. The activation of defence genes after contact with avirulence gene products of pathogens depends on signals transduced by leucine-rich repeats (LRRs) contained in resistance genes. Additionally, LRRs play roles for various actions following ligand recognition. Polygalacturonase inhibiting proteins (PGIPs), the only plant LRR protein with known ligands, are pectinase inhibitors, bound by ionic interactions to the extracellular matrix (ECM) of plant cells. They have a high affinity for fungal endopolygalacturonases (endoPGs). PGIP genes are organised in families encoding proteins with similar physical characteristics but different specificities. They are induced by infection and stress related signals. The molecular basis of PG-PGIP interaction serves as a model to understand the evolution of plant LRR proteins in recognising non-self-molecules. Extensins form a different class of structural proteins with repetitive sequences. They are also regulated by wounding and pathogen infection. Linkage of extensins with LRR motifs is highly significant in defending host tissues against pathogen invasion. Overexpression of PGIPs or expression of several PGIPs in a plant tissue, and perhaps manipulation of extensin expression could be possible strategies for disease management.
authors.affiliation: Hill Area Tea Science Division, Institute of Himalayan Bioresource Technology, Palampur 176 061, Himachal Pradesh, India. shanpatho@yahoo.com
authors.forename: V
authors.initials: V
authors.lastname: Shanmugam
mesh_terms: D005109:Extracellular Matrix / Q000378:metabolism; D005786:Gene Expression Regulation; D017343:Genes, Plant; D000090263:Leucine-Rich Repeat Proteins; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011096:Polygalacturonase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics / Q000502:physiology
chemical_list: D000090263:Leucine-Rich Repeat Proteins; C081479:PGIP protein, plant; D010940:Plant Proteins; D011506:Proteins; D011096:Polygalacturonase