Rapid and Transient Activation of a Myelin Basic Protein Kinase in Tobacco Leaves Treated with Harpin from Erwinia amylovora

Abstract

85-88). Activity of a 49-kD Mg2+-dependent and Caz+-independent kinase in tobacco leaves increased 50-fold 15 min after infiltration of harpin from Erwinia amylovora (harpin,,).Much less pronounced and more transient activation was detected in water-infiltrated leaves. Biochemical characteristics of the harpin,,-activated protein kinase (HAPK) activity are consistent with those of the mitogenactivated protein kinase family. HAPK is cytosolic and phosphorylates myelin basic protein on serine/threonine residues. Treatment with a protein tyrosine phosphatase completely eliminated HAPK activity, suggesting that tyrosine phosphorylation is required for posttranslational activation. Sustained HAPK activation after cycloheximide treatment implies that HAPK may be negatively regulated by a translation-dependent mechanism. The extracellular Ca2+ chelator ECTA or the protein kinase inhibitor K252a, infiltrated in planta together with harpinEa, partially blocked HAPK activation. The Ca2+-channel blocker La3+ had no effect on HAPK activation, suggesting that phosphorylation events precede and/or do not depend on the entry of extracellular CaZ+ into the cell. These results suggest that early signal transduction events during harpin,,-induced hypersensitive response elicitation depend in part on the activation of HAPK.

Antagonistic action of harpin proteins: HrpWea from Erwinia amylovora suppresses HrpNea-induced cell death in Arabidopsis thaliana

“…The mechanisms by which harpins provoke HR cell death have been extensively studied. Harpins trigger closely related signal transduction mechanisms such as mitogen-activated protein kinase (MAPK) activation (Adam et al, 1997;Desikan et al, 1999), cytosolic [Ca 2+ ] elevation (He et al, 1994;Pike et al, 1998;Blume et al, 2000;Cessna et al, 2001), active oxygen species (AOS) production (Baker et al, 1993;Desikan et al, 1996;Reboutier et al, 2007) and ion flux modulations (Desikan et al, 1999;Popham et al, 1995;El-Maarouf et al, 2001;Reboutier et al, 2005;Reboutier et al, 2007). Particular harpins possess a C-terminal domain that is homologous to class III pectate lyases.…”

Partial purification of elicitors from Lentinula edodes basidiocarps protecting cucumber seedlings against Colletotrichum lagenarium

“…The harpin is synthesized by Erwinia amylovora, Pseudomonas syringae and others plant-pathogenic bacteria, and represents a pathogenicity factor for those microorganisms during the interaction with their hosts. On other hand, harpin causes a hypersensitive reaction (HR) when it is infiltrated into the intercellular space of non-host species (1,24). The foliar application of harpin does not cause a visible HR, but it activates plant defense responses, inducing systemic resistance in Arabidopsis thaliana against P. syringae pv.…”

“…Effect of pooled fractions (peaks), obtained from the fractionation of the precipitate p40-80 of Lentinula edodes by anion exchange chromatography (Fig. 1), on anthracnose severity in cucumber seedlings 1 The commercial use of a protein-elicitor started with the discovery of harpin, a 44 kDa protein rich in glicin and heatstable. The harpin is synthesized by Erwinia amylovora, Pseudomonas syringae and others plant-pathogenic bacteria, and represents a pathogenicity factor for those microorganisms during the interaction with their hosts.…”

Elicitor signal transduction that leads to hypersensitive reaction in cultured tobacco cells.

“…Based on such biochemical features, this kinase has been postulated to be a member of the mitogen -activated protein kinase (MAPK) family (Chasan, 1995;Suzuki and Shinshi, 1995;Hirt,1997;Mizoguchi et al, 1997;Suzuki et al, 1999). It has also been demonstrated that fungal and bacterial elicitors activate MAPKs and MAPK-like kinases in tobacco cells (Adam et al, 1997;Lebrun -Garcia et al, 1998;Zhang et al, 1998;Romeis, et al, 1999). In parsley, an elicitor -responsive MAPK is probably involved in the activation of transcription of genes since it is translocated to the nucleus upon treatment of cells with elicitor (Ligterink et al, 1997).…”

“…In contrast to TvX-induced slow and prolonged activation of p47 protein kinase (Suzuki et al, 1999), the immediate and transient nature of the activation that occurs in response to fungal elicitors appears to be a common feature of various myelin basic protein kinases including MAPKs (Suzuki and Shinshi, 1995;Adam et al, 1997;Ligterink et al, 1997;Zhang et al,1998). Both synthesis of protein de novo and protein phosphatase activity might be required for the attenuation of p47 kinase activity and other MAPKs (Suzuki andShinshi, 1995, Meskiene et al, 1998).…”