Insights into Populus XIP aquaporins: evolutionary expansion, protein functionality, and environmental regulation

Abstract

A novel category of major intrinsic proteins which share weak similarities with previously identified aquaporin subfamilies was recently identified in land plants, and named X (for unrecognized) intrinsic proteins (XIPs). Because XIPs are still ranked as uncharacterized proteins, their further molecular characterization is required. Herein, a systematic fine-scale analysis of XIP sequences found in flowering plant databases revealed that XIPs are found in at least five groups. The phylogenetic relationship of these five groups with the phylogenetic organization of angiosperms revealed an original pattern of evolution for the XIP subfamily through distinct angiosperm taxon-specific clades. Of all flowering plant having XIPs, the genus Populus encompasses the broadest panel and the highest polymorphism of XIP isoforms, with nine PtXIP sequences distributed within three XIP groups. Comprehensive PtXIP gene expression patterns showed that only two isoforms (PtXIP2;1 and PtXIP3;2) were transcribed in vegetative tissues. However, their patterns are contrasted, PtXIP2;1 was ubiquitously accumulated whereas PtXIP3;2 was predominantly detected in wood and to a lesser extent in roots. Furthermore, only PtXIP2;1 exhibited a differential expression in leaves and stems of drought-, salicylic acid-, or wounding-challenged plants. Unexpectedly, the PtXIPs displayed different abilities to alter water transport upon expression in Xenopus laevis oocytes. PtXIP2;1 and PtXIP3;3 transported water while other PtXIPs did not.

Genome-wide identification and characterization of aquaporin gene family in common bean (Phaseolus vulgaris L.)

“…For phylogenetic analysis and nomenclature, Arabidopsis and Populus trichocarpa (Johanson et al 2001;Lopez et al 2012) aquaporin protein sequences, with their proposed nomenclature, were aligned with the P. vulgaris aquaporins using MUSCLE. A Bio Neighbor-Joining (BioNJ) tree, based on observed distance with 1000 bootstrap replicates, was built.…”

Fungal aquaporins: cellular functions and ecophysiological perspectives

“…Nevertheless, as only a very small fraction (0.6 %) of the fungal orthodox AQPs is functionally characterized, a general prediction is too early. Apart from direct analysis of protein function, modeling of the tertiary structures of these proteins (Ludewig and Dynowski 2009) (Lopez et al 2012). With only 150 members found in all investigated fungal genomes (Table 1) and an average of 0.3 members/genome over all fungal genomes, XIPs represent the smallest fungal MIP group (only 9.7 % of all deduced proteins; Fig.…”

Aquaporins: Highly Regulated Channels Controlling Plant Water Relations

“…While the PIP, TIP, NIP, and SIP subfamilies are present in all land plants, including the moss Physcomitrella patens, the XIP subfamily, identified in a wide variety of nonvascular and vascular plants, is absent in Brassicaceae and monocots (Borstlap, 2002;Danielson and Johanson, 2008;Gupta and Sankararamakrishnan, 2009;Sade et al, 2009;Shelden et al, 2009;Park et al, 2010;Lopez et al, 2012). The large number of plant aquaporins has been explained by their importance in regulating water flow through the plant body and in maintaining cellular water homeostasis at all developmental stages and in all environmental conditions (Hachez et al, 2006b).…”