The alphabet soup of plant intracellular signalling: enter cyclic nucleotides.

Recent work reveals a role for cyclic nucleotides as secondary signalling molecules in a variety of signal transduction pathways in plants. Evidence is accumulating that cGMP is involved in signalling during photomorphogenesis and that cADP-ribose triggers the release of sequestered Ca2+ during the response of plant cells to abscisic acid. Though more tentative, cAMP has been proposed as playing an important role in ion channel activity and cell cycle progression. Taken together, a picture emerges of differing signalling pathways, possibility interacting with each other, acting on an array of developmental processes.