A chemical-genetic approach for functional analysis of plant protein kinases.

Plant genomes encode hundreds of protein kinases, yet only for a small fraction of them precise functions and phosphorylation targets have been identified. Recently, we applied a chemical-genetic approach to sensitize the tomato serine/threonine kinase Pto to analogs of PP1, an ATP-competitive and cell-permeable small-molecule inhibitor. The Pto kinase confers resistance to Pst bacteria by activating immune responses upon specific recognition of bacterial effectors.

Bypassing kinase activity of the tomato Pto resistance protein with small molecule ligands.

The tomato (Solanum lycopersicum) protein kinase Pto confers resistance to Pseudomonas syringae pv. tomato bacteria expressing the AvrPto and AvrPtoB effector proteins. Pto specifically recognizes both effectors by direct physical interactions triggering activation of immune responses.

A second-site suppressor strategy for chemical genetic analysis of diverse protein kinases.

Chemical genetic analysis of protein kinases involves engineering kinases to be uniquely sensitive to inhibitors and ATP analogs that are not recognized by wild-type kinases. Despite the successful application of this approach to over two dozen kinases, several kinases do not tolerate the necessary modification to the ATP binding pocket, as they lose catalytic activity or cellular function upon mutation of the 'gatekeeper' residue that governs inhibitor and nucleotide substrate specificity. Here we describe the identification of second-site suppressor mutations to rescue the activity of 'intolerant' kinases.

Molecular properties of the Xanthomonas AvrRxv effector and global transcriptional changes determined by its expression in resistant tomato plants.

The Xanthomonas campestris pv. vesicatoria avirulence gene AvrRxv specifies resistance on the tomato line Hawaii 7998 by interacting with three nondominant plant resistance genes. AvrRxv molecular properties that impinge on its avirulence activity were characterized and transcriptional changes caused by AvrRxv expression in resistant tomato plants were extensively examined.

Identification and expression profiling of tomato genes differentially regulated during a resistance response to Xanthomonas campestris pv. vesicatoria.

The gram-negative bacterium Xanthomonas campestris pv. vesicatoria is the causal agent of spot disease in tomato and pepper. Plants of the tomato line Hawaii 7981 are resistant to race T3 of X.

LeMPK3 is a mitogen-activated protein kinase with dual specificity induced during tomato defense and wounding responses.

Mitogen-activated protein (MAP) kinase cascades are readily activated during the response of plants to avirulent pathogens or to pathogen-derived elicitors. Here we show that the tomato MAP kinase LeMPK3 is specifically induced at the mRNA level during elicitation of the hypersensitive response in resistant plants infected by avirulent strains of the phytopathogenic bacteria Xanthomonas campestris pv. vesicatoria and Pseudomonas syringae pv.