Regulation of aquaporins in plants under stress

Abstract

Aquaporins (AQP) are channel proteins belonging to the Major Intrinsic Protein (MIP) superfamily that play an important role in plant water relations. The main role of aquaporins in plants is transport of water and other small neutral molecules across cellular biological membranes. AQPs have remarkable features to provide an efficient and often, specific water flow and enable them to transport water into and out of the cells along the water potential gradient. Plant AQPs are classified into five main subfamilies including the plasma membrane intrinsic proteins (PIPs), tonoplast intrinsic proteins (TIPs), nodulin 26 like intrinsic proteins (NIPs), small basic intrinsic proteins (SIPs) and X intrinsic proteins (XIPs). AQPs are localized in the cell membranes and are found in all living cells. However, most of the AQPs that have been described in plants are localized to the tonoplast and plasma membranes. Regulation of AQP activity and gene expression, are also considered as a part of the adaptation mechanisms to stress conditions and rely on complex processes and signaling pathways as well as complex transcriptional, translational and posttranscriptional factors. Gating of AQPs through different mechanisms, such as phosphorylation, tetramerization, pH, cations, reactive oxygen species, phytohormones and other chemical agents, may play a key role in plant responses to environmental stresses by maintaining the uptake and movement of water in the plant body.

Elucidating the Possible Involvement of Maize Aquaporins in the Plant Boron Transport and Homeostasis Mediated by Rhizophagus irregularis under Drought Stress Conditions

“…Posttranslational modifications are key to achieving such a rapid and reversible regulation [59], and they affect protein stability, catalytic activity, interaction with other proteins or subcellular localization. Phosphorylation and dephosphorylation are considered key mechanisms regulating the gating of aquaporins and, consequently, their activity [61]. The open state is maintained by phosphorylation in different residues.…”

“…Kinases and phosphatases are involved in this regulation. There have been found more than 70 different sites of phosphorylation in PIPs, TIPs and NIPs, where the loop B and the N-and C-terminal tails of aquaporins are important sites in channel regulation, often involving serine residues [61,64]. Apart from phosphorylation, other posttranslational modifications have been found to modify aquaporin activity, localization and degradation, such as herteromerization, subcellular trafficking, N-terminal modification, deamidation, glycosylation, methylation or ubiquitination, although most of them are not fully understood and need additional research [13,64].…”

Defoliation-induced compensatory transpiration is compromised in SUT4-RNAi Populus

“…A number of studies suggest that dynamic adjustments in hydraulic conductivity depend on the expression of aquaporins 340 (Cochard et al 2007;Pou et al 2013;Liu et al 2014). Aquaporins form pores in membranes that allow water to move intracellularly or across membranes and through tissues toward 342 locations of lower water potential (Kapilan et al 2018). The degree to which such adjustments can alter hydraulic conductivity will also depend on anatomical traits that differ between 344 species and dictate the mass movement of water within tissues, or a plant's vulnerability to embolism and hydraulic failure (Zwieniecki et al 2007;Blackman et al 2009).…”

The involvement of calmodulin and protein kinases in the upstream of cytosolic and nucleic calcium signaling induced by hypoosmotic shock in tobacco cells

“…11 Endogenous protein kinase A and CDPKs are two protein kinases potentially responsible for phosphorylation of aquaporins, 34,35 enhanced movement of water through plasmas membrane in plant cells by maintaining the aquaporin pores at open state. [36][37][38] Upon Hypo-OS, the activation of aquaporin channels allows the movement of bulk water into intracellular space and thus causes the mechanical stretching of plasma membrane, followed by the influx of Ca 2+ from extracellular through mechano-sensitive calcium channels. According to earlier works, staurosporine and K252a, which are the protein kinase inhibitors by acting at the ATP-binding site or the catalytic domain of protein kinases, 24,39 may indirectly block the aquaporin water channels through inhibition of protein kinase A and CDPKs.…”