Aquaporins (AQPs) are membrane-spanning channel proteins with exciting applications for plant engineering and industrial applications. Translational outcomes will be improved by better understanding the extensive diversity of plant AQPs. However, AQP gene families are complex, making exhaustive identification difficult, especially in polyploid species. The allotetraploid species of Nicotiana tabacum (Nt; tobacco) plays a significant role in modern biological research and is closely related to several crops of economic interest, making it a valuable platform for AQP research. Recently, De Rosa et al., (2020) and Ahmed et al., (2020), concurrently reported on the AQP gene family in tobacco, establishing family sizes of 76 and 88 members, respectively. The discrepancy highlights the difficulties of characterizing large complex gene families. Here, we identify and resolve the differences between the two studies, clarify gene models, and yield a consolidated collection of 84 members that more accurately represents the complete NtAQP family. Importantly, this consensus NtAQP collection will reduce confusion and ambiguity that would inevitably arise from having two different descriptive studies and sets of NtAQP gene names. This report also serves as a case study, highlighting and discussing variables to be considered and refinements required to ensure comprehensive gene family characterizations, which become valuable resources for examining the evolution and biological functions of genes.

Water passes through cell membranes relatively slowly by diffusion. In order to maintain water homeostasis, the rapid and specific regulation of cellular water flow is mediated by the aquaporin (AQP) family of membrane protein water channels. The wide range of tissues that are known to express AQPs is reflected by their involvement in many physiological processes and diseases; thirteen human AQPs have been identified to date and the majority are highly specific for water while others show selectivity for water, glycerol and other small solutes. Receptor mediated translocation, via hormone activation, is an established method of AQP regulation, especially for AQP2. There is now an emerging consensus that the rapid and reversible translocation of other AQPs from intracellular vesicles to the plasma membrane, triggered by a range of stimuli, confers altered membrane permeability thereby acting as a regulatory mechanism. This review examines the molecular components that may enable such AQP regulation; these include cytoskeletal proteins, kinases, calcium and retention or localization signals. Current knowledge on the dynamic regulation of sub-cellular AQP translocation in response to a specific trigger is explored in the context of the regulation of cellular water flow.