Evolutionary and Predictive Functional Insights into the Aquaporin Gene Family in the Allotetraploid Plant Nicotiana tabacum.

Jahed Ahmed,François Chaumont,Sébastien Mercx,Marc Boutry

doi:10.3390/ijms21134743

Jahed Ahmed, François Chaumont + Show 2 more

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https://doi.org/10.3390/ijms21134743

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Abstract

Aquaporins (AQPs) are a class of integral membrane proteins that facilitate the membrane diffusion of water and other small solutes. Nicotiana tabacum is an important model plant, and its allotetraploid genome has recently been released, providing us with the opportunity to analyze the AQP gene family and its evolution. A total of 88 full-length AQP genes were identified in the N. tabacum genome, and the encoding proteins were assigned into five subfamilies: 34 plasma membrane intrinsic proteins (PIPs); 27 tonoplast intrinsic proteins (TIPs); 20 nodulin26-like intrinsic proteins (NIPs); 3 small basic intrinsic proteins (SIPs); 4 uncharacterized X intrinsic proteins (XIPs), including two splice variants. We also analyzed the genomes of two N. tabacum ancestors, Nicotiana tomentosiformis and Nicotiana sylvestris, and identified 49 AQP genes in each species. Functional prediction, based on the substrate specificity-determining positions (SDPs), revealed significant differences in substrate specificity among the AQP subfamilies. Analysis of the organ-specific AQP expression levels in the N. tabacum plant and RNA-seq data of N. tabacum bright yellow-2 suspension cells indicated that many AQPs are simultaneously expressed, but differentially, according to the organs or the cells. Altogether, these data constitute an important resource for future investigations of the molecular, evolutionary, and physiological functions of AQPs in N. tabacum.

Highlights

Aquaporins (AQPs), known as major intrinsic proteins (MIPs), are small integral membrane proteins present in almost all living organisms [1,2]
By screening the N. sylvestris (Ns). tabacum genome databases, we identified 88 complete AQP genes, almost twice the number of AQP genes identified in tomato and potato [3,7]
The number of AQP homologs always varies between plant species, the dicot plant genomes usually encoding more homologs than the monocot plants, except for the 68 full-length AQP genes found in P. virgatum, a polyploid monocot species [9]

Summary

Introduction

Aquaporins (AQPs), known as major intrinsic proteins (MIPs), are small integral membrane proteins present in almost all living organisms [1,2]. Plants maintain a large and diverse AQP family compared to mammals. Based on phylogenetic analysis and subcellular localization, vascular plant AQPs are categorized into five subfamilies: (1) plasma membrane intrinsic proteins (PIPs); (2) tonoplast intrinsic proteins (TIPs); (3) nodulin-26-like intrinsic proteins (NIPs); (4) small basic intrinsic proteins (SIPs); (5) uncharacterized X intrinsic proteins (XIPs). To date, the latter subfamily has not been found in Brassicaceae and in monocots [14,15]. AQPs from various plants are involved in transmembrane water conductance in numerous physiological processes, such as cell water homeostasis, root water uptake from the soil, root and leaf hydraulic conductance, lateral root emergence, motor cell movement, rapid internode elongation, the diurnal regulation of leaf movements, and petal development and movement [1,2,24,25,26,27,28,29]

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