Abstract
Cellular aquaporin water channels (AQPs) constitute a large family of transmembrane proteins present throughout all kingdoms of life, playing important roles in the uptake of water and many solutes across the membranes. In olive trees, AQP diversity, protein features and their biological functions are still largely unknown. This study focuses on the structure and functional and evolution diversity of AQP subfamilies in two olive trees, the wild species Olea europaea var. sylvestris (OeuAQPs) and the domesticated species Olea europaea cv. Picual (OleurAQPs), and describes their involvement in different physiological processes of early plantlet development and in biotic and abiotic stress tolerance in the domesticated species. A scan of genomes from the wild and domesticated olive species revealed the presence of 52 and 79 genes encoding full-length AQP sequences, respectively. Cross-genera phylogenetic analysis with orthologous clustered OleaAQPs into five established subfamilies: PIP, TIP, NIP, SIP, and XIP. Subsequently, gene structures, protein motifs, substrate specificities and cellular localizations of the full length OleaAQPs were predicted. Functional prediction based on the NPA motif, ar/R selectivity filter, Froger’s and specificity-determining positions suggested differences in substrate specificities of Olea AQPs. Expression analysis of the OleurAQP genes indicates that some genes are tissue-specific, whereas few others show differential expressions at different developmental stages and in response to various biotic and abiotic stresses. The current study presents the first detailed genome-wide analysis of the AQP gene family in olive trees and it provides valuable information for further functional analysis to infer the role of AQP in the adaptation of olive trees in diverse environmental conditions in order to help the genetic improvement of domesticated olive trees.
Highlights
Olive trees (Olea europaea L.) are among the most important crops around the Mediterranean basin
We investigated the transcriptional expression profile of OleurAQP genes using RNA-seq in various organs and tissues, during the early stages of olive-seedling development and the emergence of the juvenile plant and in response to biotic (Verticillium dahliae root inoculation) and abiotic stresses
The available draft genome sequence of olive trees provided us with an opportunity to analyze the aquaporin water channels (AQPs) gene family in an oleaginous species and to assess their diversification in the Olea genus, and vis-a-vis its related Oleaceae common ash (F. excelsior) and some least related taxa including tomato, poplar and Arabidopsis
Summary
Olive trees (Olea europaea L.) are among the most important crops around the Mediterranean basin They are important as plant cultivation from a commercial point of view across the millennia, largely due to their multiple uses (e.g., oil, wood, ornamental uses, canned fruit, medicinal applications), and to date, as a model to study oil fruit physiology. Most cultivars of interest show a high intraspecific genetic diversity, resulting, notably, in a wide range of contrasted stress responses. In this respect, identifying the molecular mechanisms underlying various stress tolerances in this species is essential. They lead to typical symptoms of tissue water imbalances These deviant physiological situations trigger several highly specific and rapid hydraulic responses to readjust the internal water status (or the water homeostasis). Several lines of data indicate that the abiotic and biotic stresses regulate the transcript accumulation, post-translational modifications and localization of various aquaporins, which correlate with the modulation of several ecophysiological traits such as osmotic potentials or hydraulic conductivities [3]
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