Energizing the plasmalemma of marine photosynthetic organisms: the role of primary active transport

Abstract

Generation of ion electrochemical potential differences by primary active transport can involve energy inputs from light, from exergonic redox reactions and from exergonic ATP hydrolysis. These electrochemical potential differences are important for homoeostasis, for signalling, and for energizing nutrient influx. The three main ions involved are H+, Na+ (efflux) and Cl− (influx). In prokaryotes, fluxes of all three of these ions are energized by ion-pumping rhodopsins, with one archaeal rhodopsin pumping H+into the cells; among eukaryotes there is also an H+ influx rhodopsin in Acetabularia and (probably) H+ efflux in diatoms. Bacteriochlorophyll-based photoreactions export H+ from the cytosol in some anoxygenic photosynthetic bacteria, but chlorophyll-based photoreactions in marine cyanobacteria do not lead to export of H+. Exergonic redox reactions export H+ and Na+ in photosynthetic bacteria, and possibly H+ in eukaryotic algae. P-type H+- and/or Na+-ATPases occur in almost all of the photosynthetic marine organisms examined. P-type H+-efflux ATPases occur in charophycean marine algae and flowering plants whereas P-type Na+-ATPases predominate in other marine green algae and non-green algae, possibly with H+-ATPases in some cases. An F-type Cl−-ATPase is known to occur in Acetabularia. Some assignments, on the basis of genomic evidence, of P-type ATPases to H+ or Na+ as the pumped ion are inconclusive.

Inorganic carbon concentrating mechanisms in free‐living and symbiotic dinoflagellates and chromerids

“…SLC4 HCO 3 À transporters are known from the genomes of a species of the (present) Symbiodiniaceae (Aranda et al 2016), Alexandrium monilatum and Prorocentrum minimum (Hennon et al 2017) and Thoracosphaera heimii (Van de Waal et al 2013e Waal et al 2013; presumably these are expressed in the plasmalemma. The various SLC4 HCO 3 À transporters can be Na + :HCO 3 À symporters or HCO 3 À :Clantiporters; work on the dinoflagellate SLC4 is needed to determine the co-or counter-ions, and their stoichiometry (Liu et al 2015, Raven 2020, Raven and Beardall 2020, and hence the possibility that this transporter brings about active HCO 3 À influx with corresponding accumulation of HCO 3 À in the cytosol. For the organisms in which CO 2 is a major inorganic C species entering the cell, and possibly when HCO 3 À enters the cell, active HCO 3 À influx into the plastid is needed.…”

“…The various SLC4 HCO 3 − transporters can be Na + :HCO 3 − symporters or HCO 3 − :Cl ‐ antiporters; work on the dinoflagellate SLC4 is needed to determine the co‐ or counter‐ions, and their stoichiometry (Liu et al. 2015, Raven 2020, Raven and Beardall 2020), and hence the possibility that this transporter brings about active HCO 3 − influx with corresponding accumulation of HCO 3 − in the cytosol. For the organisms in which CO 2 is a major inorganic C species entering the cell, and possibly when HCO 3 − enters the cell, active HCO 3 − influx into the plastid is needed.…”

Origin of the roles of potassium in biology

“…[1] Work on ionpumping rhodopsins shows a relatively facile evolutionary interconversion among protons, sodium and chloride as the actively transported ion. [3,4] Korolev [1] focused on high osmolarity cellular environments, cells in seawater and in metazoans; the same principles apply to organisms in freshwater bacteria, e.g. the cyanobacterium Gloeobacter, with photosynthetic, respiratory and proton-pumping rhodopsin-based chemiosmotic coupling at the plasma membrane.…”

“…[ 1 ] Work on ion‐pumping rhodopsins shows a relatively facile evolutionary interconversion among protons, sodium and chloride as the actively transported ion. [ 3,4 ]…”

Research for Ocean Sustainability

“…As part of our celebration of our 100 th volume we have published a series of reviews (Dando & Southward, 2020, Rainbow, 2020, Raven & Beardall, 2020, Langstone, 2020, Hawkins et al, 2020) reflecting on subjects typical of the Journal for more than one hundred years. We encourage authors to submit review articles and will continue to welcome such reviews and the insights they provide in the future.…”