IP3 production in the hypersensitive response of lemon seedlings against Alternaria alternata involves active protein tyrosine kinases but not a G-protein

Abstract

IP 3 increase and de novo synthesis of scoparone are produced in the hypersensitive response (HR) of lemon seedlings against the fungus Alternaria alternata. To elucidate whether a G-protein and/or a protein tyrosine kinase (PTK) are involved in signal transduction leading to the production of such a defensive response, we studied the HR in this plant system after treatment with G-protein activators alone and PTK inhibitors in the presence of fungal conidia. No changes in the level of IP 3 were detected in response to the treatment with the G-protein activators cholera toxin or mastoparan, although the HR was observed in response to these compounds as determined by the scoparone synthesis. On the contrary, the PTK inhibitors lavendustin A and 2,5-dihidroxy methyl cinnamate (DHMC) not only prevented the IP 3 changes observed in response to the fungal inoculation of lemon seedlings but also blocked the development of the HR. These results suggest that the IP 3 changes observed in response to A. alternata require a PTK activity and are the result of a G-protein independent Phospholipase C activity, even though the activation of a G-protein can also lead to the development of a HR. Therefore, it appears that more than one signaling pathway may be activated for the development of HR in lemon seedlings: one involving a G-protein and the other involving a PTK-dependent PLC.

Effect of LiCl on phosphoenolpyruvate carboxylase kinase and the phosphorylation of phosphoenolpyruvate carboxylase in leaf disks and leaves of Sorghum vulgare

“…against Alternaria alternata (Ortega et al 2005). In addition, changes in the amplitude of the signal may be of signiWcance apart from its absolute value, and this is of particular relevance in calcium-related signaling (Malho et al 1998;Plieth et al 2000;Coelho et al 2002).…”

Protein Tyrosine Kinases and Protein Tyrosine Phosphatases Are Involved in Abscisic Acid-Dependent Processes in Arabidopsis Seeds and Suspension Cells

“…trisphosphate production in lemon seedlings (Ortega et al, 2005). The differences in the inhibition of RAB18 could be due to the selectivity of each inhibitor toward the PTK involved in the transduction pathway.…”

“…In maize (Zea mays), lavendustin A inhibited a DsPTK activity (Trojanek et al, 2004). In lemon (Citrus limon) seedlings, production of inositol-1,4,5-trisphosphate induced by Alternaria alternata is blocked by lavendustin A (Ortega et al, 2005). More selective inhibitors have been used to characterize the PTK activities involved in ABA signaling.…”

Evidence for the presence of non-receptor protein tyrosine kinases in algal cells

“…The past few years have seen the mechanisms used by plants to transmit extracellular signals into the cytoplasm begin to be uncovered (Kohorn 1999;Heck 2000;Chitcholtan and Garrill 2005;Ortega et al 2005). Protein phosphorylation has been demonstrated to be a prerequisite for plant cell signaling (Sokolovski et al 2005).…”

“…Inhibitors of tyrosine kinase activity slowed tip growth and affected the organization of the actin cytoskeleton, suggestive of a role of tyrosine kinases in the process of tip growth by providing a means of bidirectional signaling between the cell wall and the cytoplasm. Another recent study suggests that the changes in inositol trisphosphate level observed during the hypersensitive response of lemon seedlings against the fungus Alternaria alternata require a tyrosine kinase activity (Ortega et al 2005). Such considerations raise the expectation that plants have tyrosine kinases similar to their animal counterparts.…”