Studies on ion channel antagonist‐binding sites in sunflower protoplasts

Vallée, Nicolas; Brière, Christian; Barthou, Henri; Souvré, A.; Alibert, Gilbert

doi:10.1016/s0014-5793(97)00675-3

Cited by 21 publications

(22 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The K d is significantly lower than binding of nifedipine to outward K + channels that are present on the PM of SE , which show K d values in the range 5 to 90 mM (Terry et al, 1992;Thomine et al, 1994). We infer that binding of fl-DHP is specific to Ca 2+ channels in Vicia SE/CCs, as suggested for other plant tissues (Vallé e et al, 1997;Volk and Franceschi, 2000). Maps of fl-DHP binding showed substantial concentration of putative Ca 2+ channels at pore plasmodesma units and SE-CC junctions ( Figures 4L and 4M) and colocalized with fluorescent ER markers.…”

Section: Ca 2+ Channels Act As Relay Stations Between Remote Stimuli mentioning

confidence: 55%

“…Moreover, preincubation of intact phloem tissue in 500 mM of unlabeled nifedipine strongly reduced the fluorescence of fl-DHP, suggesting that nifedipine and the fl-DHP compete for the same binding site and does not simply reflect partitioning into a lipid environment. This has been taken to indicate that DHP is specifically binding to Ca 2+ channels in other systems (Vallé e et al, 1997). Nevertheless, nifedipine also inhibits outward K + channels in patch-clamp studies at higher micromolar concentrations (e.g., Terry et al, 1992;Thomine et al, 1994).…”

Section: Cellular and Subcellular Localization Of Ca 2+ Channels In Sesmentioning

confidence: 99%

See 1 more Smart Citation

Sieve Element Ca2+ Channels as Relay Stations between Remote Stimuli and Sieve Tube Occlusion inVicia faba

et al. 2009

View full text Add to dashboard Cite

Damage induces remote occlusion of sieve tubes in Vicia faba by forisome dispersion, triggered during the passage of an electropotential wave (EPW). This study addresses the role of Ca 2+ channels and cytosolic Ca 2+ elevation as a link between EPWs and forisome dispersion. Ca 2+ channel antagonists affect the initial phase of the EPW as well as the prolonged plateau phase. Resting levels of sieve tube Ca 2+ of ;50 nM were independently estimated using Ca 2+ -selective electrodes and a Ca 2+ -sensitive dye. Transient changes in cytosolic Ca 2+ were observed in phloem tissue in response to remote stimuli and showed profiles similar to those of EPWs. The measured elevation of Ca 2+ in sieve tubes was below the threshold necessary for forisome dispersion. Therefore, forisomes need to be associated with Ca 2+ release sites. We found an association between forisomes and endoplasmic reticulum (ER) at sieve plates and pore-plasmodesma units where highaffinity binding of a fluorescent Ca 2+ channel blocker mapped an increased density of Ca 2+ channels. In conclusion, propagation of EPWs in response to remote stimuli is linked to forisome dispersion through transiently high levels of parietal Ca 2+ , release of which depends on both plasma membrane and ER Ca 2+ channels.

show abstract

Section: Ca 2+ Channels Act As Relay Stations Between Remote Stimuli mentioning

confidence: 55%

Section: Cellular and Subcellular Localization Of Ca 2+ Channels In Sesmentioning

confidence: 99%

Sieve Element Ca2+ Channels as Relay Stations between Remote Stimuli and Sieve Tube Occlusion inVicia faba

et al. 2009

View full text Add to dashboard Cite

show abstract

“…14 Fluorescently-tagged phenylalkylamines and dihydropyridines have earlier been used to localize putative L-type calcium channel activity sites in animal cells 15,16 and some plant cells. [17][18][19][20] Present findings provide first report on the existence of and development-associated preferential expression of PAA-binding putative calcium channel proteins on/around oil bodies in protoplasts from dark-grown seedling cotyledons of sunflower. This has been achieved by co-localization studies using epifluorescence microscopy and further confirmed by confocal laser scanning microscopy.…”

Section: Introductionmentioning

confidence: 57%

“…Phenylakylamines (PAA) and dihydropyridines (DHP) are pharmacological drugs that have routinely been used to localize calcium channels in plants [18][19][20] and animal cells. 15,16 Sufficient evidence is now available to indicate that phenylalkylamines (PAA) are specific antagonists for L-type calcium channels and they bind with α1 subunit of calcium channels.…”

Section: Resultsmentioning

confidence: 99%

Co-localization of putative calcium channels (phenylalkylamine-binding sites) on oil bodies in protoplasts from dark-grown sunflower seedling cotyledons

Vandana

Bhatla

2009

Plant Signaling & Behavior

View full text Add to dashboard Cite

IntroductionOilseeds store oil in the form of triacylglycerols (TAGs) in the organelles known as oil bodies. TAGs are rapidly converted to soluble metabolites via specialized metabolic pathways upon initiation of seed germination. 1 The protein constituents of oil bodies belong to the three major groups, comprising of structural proteins (oleosins and caleosins), enzymes (steroleosins and lipases) and minor proteins, like aquaporins. 2 The sequence of events prior to TAG hydrolysis by lipases to produce free fatty acids and glycerol, involves degradation of oleosins by a 65 kDa thiol protease 3,4 and phospholipid degradation by phospholipases. 5 This renders TAG matrix susceptible to lipase action. Oleosins are known to provide stability to oil bodies while caleosins play an important role in the biogenesis and degradation of oil bodies. 6,7 Calcium binding capacity of caleosins has been demonstrated in Arabidopsis and Sesamum indicum. 8,9 Recently, calcium concentrations as low as 100 nM have been shown to strongly modify the shape and aggregation state of purified oil bodies, thereby establishing the role of caleosins not only as a target for calcium-binding in artificial and purified oil bodies, but also as an effecter of oil body stability. 2 During seed germination, caleosins are involved in the interaction of lipid bodies with vacuoles and, thus, they play a role in the mobilization of storage lipids. 10 Based on these findings and observations from the author's laboratory on calcium-dependent proteolysis, the possibility of cation channels on/around the oil body surface for facilitating calcium availability could not be ruled out.In plant cells, ion channels permeable to Ca 2+ are so far known to exist on the plasma membrane, endoplasmic reticulum, tonoplast, nuclear and plastid membranes. 11 Electrophysiological studies have elucidated that plants possess Ca 2+ channels with different types of gating mechanisms, namely ligand-, voltageand stretch-activated. 12 Ca 2+ channels in plant cells are similar to the L-type channels characterized in animal systems. 13

show abstract

“…1992). Recently, this probe was used to label PAA binding sites in sunflower protoplasts (Vall6e et al 1997). Although Ca2+-channel-active drugs may not be highly specific in plant cells (Terry et al 1992, Thomine et al 1994, PAA has been shown to block calcium to enter into plant cells (Andrejauskas et al 1985, Graziana et al 1988, Harvey et al 1989, Thuleau et al 1990).…”

Section: Introductionmentioning

confidence: 99%

In vivo labeling of sunflower embryonic tissues by fluorescently labeled phenylalkylamine

et al. 1999

View full text Add to dashboard Cite

Summary. A fluorescently labeled phenylalkylamine, DM-Bodipy PAA, was used as a probe for the in vivo detection of ion channels in embryonic and nonembryonic tissues of sunflower. Zygotic embryos, somatic embryos, callus, leaves, roots, and shoots were analysed. Fluorescence intensity in the tissues was determined with cytofluorometry and confoeal microscopy. DM-Bodipy PAA intensively labeled the protoderm and epidermis cells in both zygotic and somatic embryos. Callus cultures exhibited labeling on sites where somatic embryos developed. Labeling was, however, very weak in leaves, shoots, and roots, except in the root cap and in the epidermis of the root. Considering that the location of phenylalkylamine binding sites is related to the distribution of ion channels in both animal and plant cells, the high intensity of labeling observed in the protoderm and epidermis of zygotic and somatic embryos as well as in protoderm, epidermis, and caps of root tips, is consistent with the role these tissues may play in ion exchange with the environment.

show abstract

Studies on ion channel antagonist‐binding sites in sunflower protoplasts

Cited by 21 publications

References 31 publications

Sieve Element Ca2+ Channels as Relay Stations between Remote Stimuli and Sieve Tube Occlusion inVicia faba

Sieve Element Ca2+ Channels as Relay Stations between Remote Stimuli and Sieve Tube Occlusion inVicia faba

Co-localization of putative calcium channels (phenylalkylamine-binding sites) on oil bodies in protoplasts from dark-grown sunflower seedling cotyledons

In vivo labeling of sunflower embryonic tissues by fluorescently labeled phenylalkylamine

Contact Info

Product

Resources

About