The chloride channels: Silently serving the plants

Abstract

Chloride channels (CLCs), member of anion transporting proteins, are present ubiquitously in all life forms. Diverging from its name, the CLC family includes both channel and exchanger (proton‐coupled) proteins; nevertheless, they share conserved structural organization. They are engaged in diverse indispensable functions such as acid and fluoride tolerance in prokaryotes to muscle stabilization, transepithelial transport, and neuronal development in mammals. Mutations in genes encoding CLCs lead to several physiological disorders in different organisms, including severe diseases in humans. Even in plants, loss of CLC protein function severely impairs various cellular processes critical for normal growth and development. These proteins sequester Cl− into the vacuole, thus, making them an attractive target for improving salinity tolerance in plants caused by high abundance of salts, primarily NaCl. Besides, some CLCs are involved in NO3− transport and storage function in plants, thus, influencing their nitrogen use efficiency. However, despite their high significance, not many studies have been carried out in plants. Here, we have attempted to concisely highlight the basic structure of CLC proteins and critical residues essential for their function and classification. We also present the diverse functions of CLCs in plants from their first cloning back in 1996 to the knowledge acquired as of now. We stress the need for carrying out more in‐depth studies on CLCs in plants, for they may have future applications towards crop improvement.

Understanding the potential of root microbiome influencing salt‐tolerance in plants and mechanisms involved at the transcriptional and translational level

“…SLAC1, together with the other homologs, are also known to regulate the transport of Cl − in guard cells along with the acquisition by the roots (Hedrich & Geiger, 2017). Several genes encoding CLC channels have been found in Arabidopsis and rice, and almost all have been characterized for their Cl − transport inside the vacuoles and other organelles; however, none of them is known to be present in the plasma membrane (Subba et al, 2021; Teakle & Tyerman, 2010). However, Cl − efflux from the cells is facilitated by the function of several aquaporins and ABC transporters present in the plasma membrane (Teakle & Tyerman, 2010).…”

Genome and Transcriptome Sequencing of Populus × sibirica Identified Sex-Associated Allele-Specific Expression of the CLC Gene

“…CLC genes participate in Cl – and NO 3 – transport, are involved in response to salt stress, and are related to the efficiency of nitrogen use in plants ( Liao et al, 2018 ; Liu et al, 2020 ; Subba et al, 2020 ). Therefore, differences in CLC expression in vegetative tissues of P. × sibirica could be of interest in terms of determination of the possible role of sex in adaptation to particular environments.…”

Plant Proton Pumps and Cytosolic pH-Homeostasis

“…to the tonoplast and the plasma membrane (Isner et al, 2018;van Kleeff et al, 2018;Subba et al, 2020) or the SOS2/SOS3 complex, which activates cation-proton-antiporters (NHX, CAX), V-ATPase, and PPase (Shabala et al, 2020). Other candidates are MAPKs, which might act on transporters, too (Cubero-Font and de Angeli, 2020).…”

“…Proton pumps, potassium-channels, and CLC-proteins are target of phosphorylation. Kinases might act on proteins in different membranes, such as the receptor-like kinase KIN7, which locates to the tonoplast and the plasma membrane ( Isner et al, 2018 ; van Kleeff et al, 2018 ; Subba et al, 2020 ) or the SOS2/SOS3 complex, which activates cation-proton-antiporters (NHX, CAX), V-ATPase, and PPase ( Shabala et al, 2020 ). Other candidates are MAPKs, which might act on transporters, too ( Cubero-Font and de Angeli, 2020 ).…”

“…Other candidates are MAPKs, which might act on transporters, too ( Cubero-Font and de Angeli, 2020 ). Together with membrane-associated phosphatases they seem to be key players of transport regulation: PP2A dephosphorylates CLC-a ( Subba et al, 2020 ), PP2A-C5 interacts with the vacuolar CLCs -a, -b, -c, and –g ( Hu et al, 2017 ). Inhibition of PP2C.D keeps PM-ATPase active ( Spartz et al, 2017 ), what is in good agreement with auxin-dependent inactivation of PP2C-D1 manner by SMALL AUXIN UP RNA 19 (SAUR19) for regulating AHA1 and AHA2 in A. thaliana ( Mangano et al, 2018 ; Ren et al, 2018 ).…”