Electrophysiological localization of blue light sensory sites in etiolated dicotyledon seedlings

Abstract

Changes induced by blue light (BL) in ion fluxes and pH in etiolated seedlings of dicotyledons ( Cucumis sativus L., Phaseolus lunatus L., Pisum sativum L.) were studied using a non-invasive ion-selective microelectrode technique (MIFE). BL induced significant Ca 2 + uptake within the first 5 min after onset in upper parts of the whole cucumber seedling. To locate the sites of the BL perception, studies on excised segments were performed. The data obtained demonstrated that the observed Ca 2 + uptake is associated with the very top of the hypocotyl hook of cucumber and butter bean, and with the whole epicotyl of pea, although the response was stronger for the upper parts of the epicotyl. Addition of Gd 3 + and La 3 + into the bathing solution completely prevented Ca 2 + influx, implicating the involvement of Ca 2 + channels in the regulation of Ca 2 + transport during BL exposure. BL-induced changes in H + and Ca 2 + fluxes were not likely to be linked to the one mechanism, as they were separated spatially and pharmacologically.

The Subcellular Localization and Blue-Light-Induced Movement of Phototropin 1-GFP in Etiolated Seedlings of Arabidopsis thalianaw

“…The overall changes lasted less than 100 s. However, a single blue-light pulse desensitized the system to subsequent pulses and recovery took place over 3-4 h, not unlike the dark recovery to a strict localization of PHOT1::GFP at the plasma membrane reported in the present study. Two groups have reported blue-light-induced increases in calcium uptake by etiolated tissues of Arabidopsis (Stoelzle et al, 2003) and several other dicot species (Babourina et al, 2003), respectively. Stoelzle et al (2003) found the response strongly reduced in a phot1-5 mutant and completely absent in a phot1-5 phot2-1 double mutant.…”

“…RPT2 (a member of the same protein family as NPH3) is required both for phototropism and stomatal opening, but not for chloroplast relocation (Inada et al, 2004). In addition, cytoplasmic concentrations of Ca 2+ , K + , Na + , Cl -, and H + can change during phototropinmediated blue-light signaling, indicating that changes in some ion channels and/or pumps are mediated by phototropins (Babourina et al, 2003;Baum et al, 1999;Fuchs et al, 2003;Harada et al, 2003;Stoelzle et al, 2003). Recent studies indicate that phot1 plays a role in drought tolerance in Arabidopsis (Galen et al, 2007).…”

Ion flux kinetics in blue light‐grown field dodder (Cuscuta campestris) seedlings

“…) and the localisation of BL receptors (Babourina et al . ) in a range of plant species, as well as for revealing the association between light‐induced transient ion fluxes and leaf growth and photosynthesis (Shabala & Newman ; Shabala & Hariadi ; Živanović et al . ).…”

A novel mutant with modified tropic responses in Pisum sativum L.

“…Ten-millimetre-long segments from the upper part of the epicotyl a few millimetres below the apical hook were then harvested. Harvested material was fixed vertically in plastic holders in measuring chambers as described previously (Babourina et al 2003). Chambers were filled with the measuring solution (0.2 mM KCl, 0.1 mM CaCl 2 , pH 5.5) to approximately 5 mm above the upper cut surface of the stem.…”