Signal Perception and
Transduction

Signal transduction is an actively expanding topic of research in plant biology. Signals, which include a wide array of external and internal stimuli, are amplified and communicated by complex signal transduction networks, most of which initiate with the activation of receptor proteins. Bacterial receptor and transduction systems provide models for plant receptors, including proteins that sense ethylene and phytochrome. Among plant signal transduction pathways that have been identified are other components common to many signal transduction networks in animals, such as GTPases and phospholipid derivatives. Investigations into the roles of GTPases in plant signal transduction are still in their infancy, but already a strong relationship is implicated between GTPase activity and phospholipid signaling. Phospholipases A, C, and D influence many aspects of plant development and signaling. Cyclic nucleotides also appear to act as second messengers in plant cells and most likely interact with another second messenger, cytosolic calcium. Calcium channels and other calcium transporters form the basis of a complex Ca²⁺ signaling network in plants. Protein kinases are the most common transduction components interpreting signals in plant cells. Various classes of protein kinase act in concert with protein phosphatases to mediate plant cell signaling and control metabolism. Plant hormones are important elements in controlling plant growth and development, and progress is being made in understanding how cells transduce these signals. Advances in signal transduction research are rapidly expanding our understanding of how plant cells communicate and cooperate.