Crosstalk in cellular signaling: background noise or the real thing?

During the past two decades, molecular biologists and geneticists have deconstructed intracellular signaling pathways in individual cells, revealing a great deal of crosstalk among key signaling pathways in the animal kingdom. Fewer examples have been reported in plants, which appear to integrate multiple signals on the promoters of target genes or to use gene family members to convey signal-specific output. For both plants and animals, the question now is whether the "crosstalk" is biologically relevant or simply noise in the experimental system. To minimize such noise, we suggest studying signaling pathways in the context of intact organisms with minimal perturbation from the experimenter.