Forisome dispersion in Vicia faba is triggered by Ca2+ hotspots created by concerted action of diverse Ca2+ channels in sieve elements

Abstract

Remote-controlled Ca2+ influx, elicited by electropotential waves, triggers local signaling cascades in sieve elements and companion cells along the phloem of Vicia faba plants. The stimulus strength seems to be communicated by the rate and duration of Ca2+ influx into sieve elements (SEs). The cooperative recruitment of Ca2+ channels results in a graded response of forisome culminating in full sieve-tube occlusion. Several lines of evidence are integrated into a model that links the mode and strength of the electropotential waves (EPWs) with forisome dispersion, mediated by transiently enhanced levels of local Ca2+ release dependent on both plasma membrane and ER Ca2+ channels. © 2009 Landes Bioscience.