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Plant immune receptors of the class of nucleotide-binding and leucine-rich repeat domain ( NLR) proteins can contain additional domains besides canonical NB-ARC (nucleotide-binding adaptor shared by APAF-1, R proteins, and CED-4 (NB-ARC)) and leucine-rich repeat ( LRR) domains. Recent research suggests that these additional domains act as integrated decoys recognizing effectors from pathogens. Proteins homologous to integrated decoys are suspected to be effector targets and involved in disease or resistance., Here, we scrutinized 31 entire plant genomes to identify putative integrated decoy domains in NLR proteins using the Interpro search. The involvement of the Zinc Finger-BED type (ZBED) protein containing a putative decoy domain, called BED, in rice ( Oryza sativa) resistance was investigated by evaluating susceptibility to the blast fungus Magnaporthe oryzae in rice over-expression and knock-out mutants., This analysis showed that all plants tested had integrated various atypical protein domains into their NLR proteins (on average 3.5% of all NLR proteins). We also demonstrated that modifying the expression of the ZBED gene modified disease susceptibility., This study suggests that integration of decoy domains in NLR immune receptors is widespread and frequent in plants. The integrated decoy model is therefore a powerful concept to identify new proteins involved in disease resistance. Further in-depth examination of additional domains in NLR proteins promises to unravel many new proteins of the plant immune system. [ABSTRACT FROM AUTHOR]

Elevated constitutive expression of components of the defence arsenal is associated with quantitative resistance to the rice blast fungus, a phenomenon called preformed defence. While the role of many disease regulators in inducible defence systems has been extensively studied, little attention has been paid so far to genes that regulate preformed defence. In this study, we show by microarray analysis across rice diversity that the preformed defence phenomenon impacts on a large number of defence-related genes without apparently affecting other biological processes. Using a guilt-by-association strategy, we identified two positive regulators that promote constitutive expression of known defence markers and partial resistance to rice blast. The HSF23 gene encodes for a putative member of the heat shock transcription factor family, while CaMBP encodes for a putative Calmodulin-binding protein. Both HSF23 and CaMBP strongly affect preformed defence and also plant growth. Additionally, we identified the OB-fold gene as a negative regulator of blast resistance, which could be involved in RNA stabilization. The OB-fold mutants do not suffer from obvious developmental defects. Taken together, our results prove that our strategy of combining analysis of gene expression diversity with guilt-by-association is a powerful way to identify disease resistance regulators in rice. [ABSTRACT FROM AUTHOR]