Cellular Basis of Electrical Potential Waves along the Phloem and Impact of Coincident Ca ²⁺ Fluxes

Involvement of the Sieve Element Cytoskeleton in Electrical Responses to Cold Shocks

“…(3) The extent to which the propagation of coldinduced electrical potential waves (Fromm and Lautner, 2007;Hafke and van Bel, 2013) has an impact on the cytoskeleton of remote SEs remains to be investigated.…”

“…therein). This Ca 2+ recruitment from internal stores, possibly by Ca 2+ -induced Ca 2+ release from smooth ER cisternae Hafke et al, 2009), may be required for the dispersion of forisomes, the ends of which seem to be in touch with the smooth ER Hafke and van Bel, 2013).…”

“…4, C and I). Such dose-dependent voltage transients may be accompanied by a transient rise in Ca 2+ permeability (Krol and Trebacz, 1999;Krol et al, 2003Krol et al, , 2004 but may not recruit sufficient Ca 2+ from internal stores to trigger a forisome response Hafke and van Bel, 2013).…”

“…For instance, K + fluxes are regulated by actin dynamics (Hwang et al, 1997;Liu and Luan, 1998;Chérel, 2004), while Ca 2+ influx into the cytoplasm appears to be mediated by voltage-dependent Ca 2+ -permeable channels associated with microtubules (Mazars et al, 1997;Thion et al, 1998) or by mechanosensitive channels possibly associated with microfilaments (Wang et al, 2004;Zhang et al, 2007). Both types of Ca 2+ -permeable channels probably reside in the SE plasma membrane (Knoblauch et al, 2001;Hafke et al, 2007Hafke et al, , 2009Furch et al, 2009), where they are likely involved in Ca 2+ -dependent systemic signaling Hafke et al, 2009;van Bel et al, 2011;Hafke and van Bel, 2013). These channels are also putative initiators of Ca 2+ -induced signal transduction in SEs, leading to sieve-plate occlusion in response to local cold shocks (Thorpe et al, 2010).…”

Signalomics: Diversity and Methods of Analysis of Systemic Signals in Plants

“…Nevertheless, they both seem to involve the same ions, being initiated by an infl ux of Ca 2+ and then an effl ux of Cl − and K + , but they differ in the magnitude and duration of these fl uxes (Davies 2006 ) and in some instances proton fl uxes are also involved in long-distance electrical signaling (Grams et al 2009 ). Although any cell with voltage-gated channels can generate and transmit signals from cell to cell (via plasmodesmata), long-distance transmission seems to be exclusive through the phloem, primarily the phloem SE (Van Bel et al 2011 ;Hafke and Van Bel 2013 ); thus, methods for "tapping" the phloem are important for electrical as well as chemical signals. APs can be evoked by any external stimulus (electrical, cold, heat, wound) or internal stimulus that can elicit a change in membrane potential suffi ciently large to activate voltage-gated channels (Davies 2006 ).…”