Vacuolar H+/Ca2+ transport: who's directing the traffic?

Physiological studies have established the role of plant high-capacity vacu olar H+/Ca2+ exchange activity in ion homeostasis and signal transduction. The molecular characterization and structure-Function analyses of these tra nsporters are just beginning to emerge. In yeast, Ca2+ signaling molecules regulate vacuolar H+/Ca2+ exchange. Recently, some of the Ca2+ dependent 'm olecular relay' molecules have been characterized in plants; however, the r egulation of pia nt vacuolar H+/Ca2+ exchange remains an open question.