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

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. Contents Summary 289 I. Introduction 289 II. Specific variations in aquaporin structures imply functional diversity 290 III. The various localization patterns and functions of intracellular aquaporins 292 IV. Concluding remarks and challenges 298 Acknowledgements 299 References 299