Decreased inositol 1,4,5-trisphosphate content in pathogen-challenged soybean cells

Phosphoinositide-specific phospholipase C (PI-PLC) has been shown to be tra nsiently activated when plant cells were treated with elicitors. We thus in vestigated the activity of PI-PLC when soybean cells were infected with the bacterial pathogen Pseudomonas syringae pv, glycinea, by measuring cellula r cytosolic inositol 1,4,5-trisphosphate (IP3) levels. We observed that IP3 content decreased in both compatible and incompatible interactions. In vit ro phosphatase activities were similar in both water control and infected c ells with slightly lower IP3 degradation observed for infected cells, indic ating that the reduced IP3 content in infected cells most likely results fr om reduced PI-PLC activity. We hypothesize that reduced IP3 content followi ng infection may lead to suppression of various housekeeping activities of the cells, thus diverting the cellular resources either to the synthesis of defense-related compounds against pathogens, and/or to the growth of patho gens.