Expression of Fragaria vesca PIP Aquaporins in Response to Drought Stress: PIP Down-Regulation Correlates with the Decline in Substrate Moisture Content

Nada Šurbanovski,Mark A Else,Daniel J Sargent,Hanma Zhang,Olga M Grant,David W Simpson,Raffaella Balestrini

doi:10.1371/journal.pone.0074945

Abstract

PIP aquaporin responses to drought stress can vary considerably depending on the isoform, tissue, species or level of stress; however, a general down-regulation of these genes is thought to help reduce water loss and prevent backflow of water to the drying soil. It has been suggested therefore, that it may be necessary for the plant to limit aquaporin production during drought stress, but it is unknown whether aquaporin down-regulation is gradual or triggered by a particular intensity of the stress. In this study, ten Fragaria PIP genes were identified from the woodland strawberry (Fragaria vesca L.) genome sequence and characterised at the sequence level. The water relations of F. vesca were investigated and the effect of different intensities of drought stress on the expression of four PIP genes, as well as how drought stress influences their diurnal transcription was determined. PIP down-regulation in the root corresponded to the level of drought stress. Moreover, transcript abundance of two genes highly expressed in the root (FvPIP1;1 and FvPIP2;1) was strongly correlated to the decline in substrate moisture content. The amplitude of diurnal aquaporin expression in the leaves was down-regulated by drought without altering the pattern, but showing an intensity-dependent effect. The results show that transcription of PIP aquaporins can be fine-tuned with the environment in response to declining water availability.

Highlights

Drought is an environmental stress that produces a plant water deficit sufficient to disturb internal physiological processes [1]
Fragaria plasma membrane intrinsic proteins (PIP) Genes Only five PIP isoforms have been characterised from the Rosaceae family so far [35][51][52][53]
Sequences showed a structure typical of plant PIP aquaporins; all had the residues of the aromatic/arginine selectivity filter conserved, pointing to water selectivity of these isoforms [19]

Summary

Introduction

Drought is an environmental stress that produces a plant water deficit sufficient to disturb internal physiological processes [1]. Physiological parameters of plant water balance, such as water potential, hydraulic resistance, stomatal conductance and transpiration, change in response to drought stress as various mechanisms start to operate in order to minimise water loss, maximise water uptake and improve plant water status. Aquaporins have been implicated in leaf water relations including mediating water transport from the xylem to the stomatal chamber [12][13] and responding to different environmental factors including water stress, cold stress and irradiance [14]

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