Evolutionary Understanding of Aquaporin Transport System in the Basal Eudicot Model Species Aquilegia coerulea.

Shweta Singh,Praveen Khatri,Pankaj Singla,S.M Shivaraj,Altaf Nadaf,Surbhi Kumawat,Rupesh Deshmukh,Vacha Bhatt,Humira Sonah,Virender Kumar,Tilak Raj Sharma

doi:10.3390/plants9060799

Abstract

Aquaporins (AQPs) play a pivotal role in the cellular transport of water and many other small solutes, influencing many physiological and developmental processes in plants. In the present study, extensive bioinformatics analysis of AQPs was performed in Aquilegia coerulea L., a model species belonging to basal eudicots, with a particular focus on understanding the AQPs role in the developing petal nectar spur. A total of 29 AQPs were identified in Aquilegia, and their phylogenetic analysis performed with previously reported AQPs from rice, poplar and Arabidopsis depicted five distinct subfamilies of AQPs. Interestingly, comparative analysis revealed the loss of an uncharacterized intrinsic protein II (XIP-II) group in Aquilegia. The absence of the entire XIP subfamily has been reported in several previous studies, however, the loss of a single clade within the XIP family has not been characterized. Furthermore, protein structure analysis of AQPs was performed to understand pore diversity, which is helpful for the prediction of solute specificity. Similarly, an AQP AqcNIP2-1 was identified in Aquilegia, predicted as a silicon influx transporter based on the presence of features such as the G-S-G-R aromatic arginine selectivity filter, the spacing between asparagine-proline-alanine (NPA) motifs and pore morphology. RNA-seq analysis showed a high expression of tonoplast intrinsic proteins (TIPs) and plasma membrane intrinsic proteins (PIPs) in the developing petal spur. The results presented here will be helpful in understanding the AQP evolution in Aquilegia and their expression regulation, particularly during floral development.

Highlights

Aquaporins (AQPs) are pore-forming membrane proteins that belong to the major intrinsic protein (MIP) family
Genome-Wide Identification, Classification and Phylogenetic Distribution of Aquaporins in Initially, a total of 35 AQPs were identified in the Aquilegia genome based on a homology search performed using known AQPs from rice, Arabidopsis, and poplar
The occurrence of only one group in the XIP subfamily suggests the possibility of an independent loss of the entire XIP family from monocots and some of the dicot families (Brassicacea, for example), and further expansion into two groups in the majority of dicots

Summary

Introduction

Aquaporins (AQPs) are pore-forming membrane proteins that belong to the major intrinsic protein (MIP) family. Aquaporins facilitate selective transport of water and many other small solutes across the biological membranes. The small solutes transported through AQPs include urea; CO2 ; H2 O2 ; and metalloids such as silicon (Si), boron (B), and germanium (Ge) [1,2]. Plants 2020, 9, 799 almost all eukaryotes and prokaryotes [3,4,5]. These proteins were first reported in the erythrocytes of mammals by Peter Agre and his colleagues in the early 1990s [6,7]. The discovery of AQPs paved the way to enhance our understanding of cellular transport systems in animals as well as in plants [1,8]

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