Ectopic Expression of Aeluropus littoralis Plasma Membrane Protein Gene AlTMP1 Confers Abiotic Stress Tolerance in Transgenic Tobacco by Improving Water Status and Cation Homeostasis.

Walid Ben Romdhane,Afif Hassairi,Jalel Azaza,Lotfi Fki,Jean-Luc Verdeil,Rania Ben-Saad,Abdullah Al-Doss,Nabil Zouari,Donaldo Meynard,Emmanuel Guiderdoni

doi:10.3390/ijms18040692

Abstract

We report here the isolation and functional analysis of AlTMP1 gene encoding a member of the PMP3 protein family. In Aeluropus littoralis, AlTMP1 is highly induced by abscisic acid (ABA), cold, salt, and osmotic stresses. Transgenic tobacco expressing AlTMP1 exhibited enhanced tolerance to salt, osmotic, H2O2, heat and freezing stresses at the seedling stage. Under greenhouse conditions, the transgenic plants showed a higher level of tolerance to drought than to salinity. Noteworthy, AlTMP1 plants yielded two- and five-fold more seeds than non-transgenic plants (NT) under salt and drought stresses, respectively. The leaves of AlTMP1 plants accumulated lower Na+ but higher K+ and Ca2+ than those of NT plants. Tolerance to osmotic and salt stresses was associated with higher membrane stability, low electrolyte leakage, and improved water status. Finally, accumulation of AlTMP1 in tobacco altered the regulation of some stress-related genes in either a positive (NHX1, CAT1, APX1, and DREB1A) or negative (HKT1 and KT1) manner that could be related to the observed tolerance. These results suggest that AlTMP1 confers stress tolerance in tobacco through maintenance of ion homeostasis, increased membrane integrity, and water status. The observed tolerance may be due to a direct or indirect effect of AlTMP1 on the expression of stress-related genes which could stimulate an adaptive potential not present in NT plants.

Highlights

Crop yield reduction due to the direct effect of drought, salt, and cold stresses was estimated as high as 70% [1]
The comparison between AlTMP1 cDNA and its amplified genomic sequence revealed that the gene contains two exons separated by one intron of 109 bp (Figure S1)
An AlTMP1 gene was isolated from the halophyte C4 grass A. littoralis

Summary

Introduction

Crop yield reduction due to the direct effect of drought, salt, and cold stresses was estimated as high as 70% [1] These stresses affect plant growth and development through osmotic stress, nutrient imbalance and the toxic effects caused by an excess of Na+ and Cl− ions [2]. Plants adjust their osmotic balance by accumulating osmolytes (betaine, glycine, and proline), maintaining succulence and secreting salt [4,5] These functions are carried out by a battery of proteins that are classified as pumps, carriers, and channels. Some genes such as NHX-type antiporters have been isolated and identified to be responsible for removing Na+ from the cytoplasm This mechanism can be performed either by the exclusion of Na+ from plant cells (plasma membrane group: SOS1 (NHX7) from Arabidopsis) or by the sequestration of Na+ in vacuoles (vacuole group: NHX1–NHX4 from Arabidopsis) [7]. The NSCCs can be divided into: cyclic-nucleotide-gated NSCCs (CNGSs), amino-acid gated NSCCs (AAG-NSCCs) and reactive-oxygen-species-activated (ROS) [10]

Methods

Results

Discussion

Conclusion