Metabolic transduction and amplification of light signals

Abstract

Any photomorphogenic response is made up of the processes of signal perception, signal transduction and amplification, and expression of morphogenic change. Transduction involves transformation of the environmental signal into a molecular or metabolic message, and may consist of a catenary sequence of events - a transduction chain during which there is substantial amplification of the message. For example, there can be a several thousand-fold increase between the number of quanta which elicit a response, and the final number of biological molecules ‘altered’ in the response; the apparent quantum yield of photomorphogenic change is considerably greater than one. Potential amplifying devices might well include regulators of metabolism and cellular activity, such as enzymes and plant growth regulators. Cell membranes, too, being both involved in the regulation of ion and metabolite transport and possible sites for photoreceptor localization, might be expected to have major roles in the transduction and amplification of light signals.