Properties of ion channels in the protoplasts of the Mediterranean seagrass Posidonia oceanica

Abstract

Posidonia oceanica (L) Delile, a seagrass endemic of the Mediterranean sea, provides food and shelter to marine organisms. As environment contamination and variation in physico-chemical parameters may compromise the survival of the few Posidonia genotypes living in the Mediterranean, comprehending the molecular mechanisms controlling Posidonia growth and development is increasingly important. In the present study the properties of ion channels in P. oceanica plasma membranes studied by the patch-clamp technique in protoplasts obtained from the young non-photosynthetic leaves were investigated. In protoplasts that were presumably originated from sheath cells surrounding the vascular bundles of the leaves, an outwardrectifying time-dependent channel with a single channel conductance of 58 ± ± ± ± 2 pS which did not inactivate, was selective for potassium and impermeable to monovalent cations such as Na + , Li + and Cs + was identified. In the same protoplasts, an inward-rectifying channel that has a timedependent component with single channel conductance of the order of 10 pS, a marked selectivity for potassium and no permeation to sodium was also identified, as was a third type of channel that did not display any ionic selectivity and was reversibly inhibited by tetraethylammonium and lanthanum. A comparison of Posidonia channel characteristics with channels identified in terrestrial plants and other halophytic plants is included.

Isolation and Expression of Two Aquaporin-Encoding Genes from the Marine Phanerogam Posidonia oceanica

“…In seagrasses, which tolerate very high Na + concentrations, this would imply very high salt concentrations within the cell, especially in the vacuole, in which high salinity is more compatible with metabolism than in the cytoplasm (Tyerman 1980). Strong Na + accumulation in the vacuoles of leaf parenchyma cells is probably related to the activity of Na + -permeable ion channels (Carpaneto et al 1997). In this respect, it is conceivable that the occurrence of tonoplast aquaporins contributes to adjust the osmotic gradient in seagrasses, as it does in terrestrial plants.…”

“…At cellular level, the main role in determining osmotic gradient is related to ion channels (Carpaneto et al 2004); however, adjustment of such gradient can be related also to water transport through aquaporins, whose efficiency can be modulated either by post-translational modifications or by modulation of aquaporin gene transcription and translation (Maurel et al 1997).…”

“…Unfortunately, only a few studies have contributed to the molecular characterization of seagrass vacuoles and their function (Pak et al 1995, Carpaneto et al 1997). Plant cells must have turgor pressure, i.e.…”

Eco-physiological responses and symbiotic nitrogen fixation capacity of salt-exposed Hedysarum carnosum plants

“…Indeed, Na + accumulation in shoots was accompanied by a significant decrease in K + concentrations. It has been suggested that Na + and K + compete for uptake at the plasma membrane level (Carpaneto et al, 2004). Hence, limited absorption of potassium impairs plant growth and development as this cation functions as a cofactor of various reactions.…”

Isolation of protoplasts and ion channel recording of plasma membrane patches and whole-cell recordings of the marine alga, Ulva pertusa (Chlorophyta)

“…Patchclamp research on higher plant species was first reported in 1984 (Schroeder et al 1984). However, the application to marine algae and plants is limited to Valonia utricularis (Heidecker et al 1999;Binder et al 2003), Coccolithus pelagicus (Taylor and Brownlee 2003) and Posidonia oceanica (Carpaneto et al 2004).…”