A look inside: localization patterns and functions of intracellular plant aquaporins

Abstract

Contents Summary289I.Introduction289II.Specific variations in aquaporin structures imply functional diversity290III.The various localization patterns and functions of intracellular aquaporins292IV.Concluding remarks and challenges298Acknowledgements299References299 Summary Aquaporins form a superfamily of intrinsic channel proteins in the plasma and intracellular membranes of plant cells. While a lot of research effort has substantiated the importance of plasma membrane aquaporins for the regulation of plant water homeostasis, comparably little is known about the function of intracellular aquaporins. Yet, various low‐molecular‐weight compounds, in addition to water, were recently shown to permeate some of these aquaporins. In this review, we examine the diversity of transport properties and localization patterns of intracellular aquaporins. The discussed profiles include, for example, water and ammonia transport across the tonoplast or CO2 transport through the chloroplast envelope. Furthermore, we try to assess to what extent the diverse aquaporin distribution patterns, in relation to the high degree of compartmentation of plant cells, can be linked to a wide range of cellular functions.

Identification of AtSM34, a novel tonoplast intrinsic protein-interacting polypeptide expressed in response to osmotic stress in germinating seedlings

“…When the GFP was fused to AtSM34∆83aa, the green fluorescent signals were distributed in both the cytoplasm and nucleus (Figure 3 To further elucidate the role of this region in the interaction with AtTIP1;1, Arabidopsis protoplasts were cotransformed with YNE-AtSM34∆83aa and YCE-AtTIP1;1. Restored YFP fluorescence was relocalized to the large central vacuolar membrane (Figure 3(b) bottom panel), which was similar to the tonoplast localizations of some TIP members in protoplasts [12]. This confirmed the N-terminus of AtSM34 as the transmembrane domain was not required for the protein-protein interaction.…”

“…Reports have indicated expression of TIPs is predominantly located in the tonoplast [12]. However, McTIP1;2 (McMIPF) proteins redistributed to the endosomes in osmotic stress [14].…”

“…Tonoplast intrinsic proteins (TIPs) were identified as a tonoplast-localized water channel subgroup [12]. Variations in TIP expression levels might influence water movement across the tonoplast and might also affect the responses of plants to abiotic stress [13].…”

Intracellular localization and physiological function of a rice Ca2+-permeable channel OsTPC1

“…A tobacco water channel, aquaporin1 (NtAQP1) shows a dual localization in the PM and the chloroplast envelope, which creates a dual function as a water channel (at the PM) or a CO 2 channel (at the chloroplast envelope). [29][30][31] Interestingly, though the VM marker protein was not detected in the PM fraction, a small portion of OsTPC1-GFP…”

Rootstock control of scion response to water stress in grapevine

“…Root hydraulic conductivity, in terms of short and long distance transport (over membranes and xylem, respectively) was considered in order to characterize the responses of the rootstocks. Aquaporins play a major role in transcellular water movement by facilitating the transport of water through cell membranes (Kaldenhoff et al, 2008;Maurel et al, 2008;Wudick et al, 2009), therefore they significantly control root hydraulic conductivity (Javot and Maurel, 2002;Lee et al, 2005;Van As, 2007;Postaire et al, 2010). Their activity was measured with the application of an inhibitor of cell metabolism, HgCl 2 , to root and leaf tissues.…”