The Arabidopsis expansin gene (AtEXPA18) is capable to ameliorate drought stress tolerance in transgenic tobacco plants.

Alireza Abbasi,Meysam Malekpour,Sajjad Sobhanverdi

doi:10.1007/s11033-021-06589-2

Abstract

Expansins are cell wall proteins loosening plant cell in pH-dependent manner. This study aimed to investigate the role of AtEXPA18 in different morphological, physiological, and cellular responses of transgenic tobacco plants to moderate and severe drought stress. Previously synthesized AtEXPA18 gene construct was successfully transferred to the tobacco plants through an agrobacterium-mediate transformation system. Upon obtaining the second generation, tobacco transgenic plants were confirmed by conventional polymerase chain reaction (PCR) technique alongside reverse transcription PCR (RT-PCR) using specific primers. Under drought stress, the transgenic lines showed remarkable growth and significantly improved based on morphological traits such as height and stem diameter, leaf area, leaf number, root dry weight, and Abscisic acid levels of leaves compared control plants. As a result, the Cytokinin content of transgenic plants has increased under severe stress levels. Notably, the area's expansion for abaxial epidermal cells under the microscope confirmed in transgene cells compared with the -transgene cells. These results, altogether, could support the AtEXPA18 gene implication in cell expansion and improving tolerance capacity of transgenic crops under drought stress.

Highlights

Throughout the world, most plant species, at least for a short period, are encountered with at least one biotic or abiotic stress
Under water deficit stress, at least two expansin genes were up-regulated at the maize's root elongation zone and help root growth constantly continue at low water potential (Wu et al 1996; Wu et al 2001)
The mature seeds of transgenic tobacco lines were successfully germinated at the selective Murashige and Skoog (MS) medium, owing to the 35S::AtEXPA18 construct expressing the kanamycin resistance gene, Neomycin phosphotransferase, whereas the wild type and non-transgenic tobacco plants were decayed after germination

Summary

Introduction

Throughout the world, most plant species, at least for a short period, are encountered with at least one biotic or abiotic stress. Expansins are a class of cell wall proteins to promote the flexibility of the plant cell wall, mainly through loosening hydrogen bonds between the cellulose microfibrils and matrix polymer (Choi et al 2008; Sampedro and Cosgrove 2005) These proteins, which firstly discovered in cucumber hypocotyls (McQueen-Mason et al 1992), usually encoded by a gene superfamily containing four sub-families: including α-expansin (EXPA), βexpansin(EXPB), expansin-like A (EXLA), and expansin-like B (EXLB) (Cosgrove 2000; Cosgrove 2015; Kende et al 2004; Marowa et al 2016). Under water deficit stress, at least two expansin genes were up-regulated at the maize's root elongation zone and help root growth constantly continue at low water potential (Wu et al 1996; Wu et al 2001). Over-expression of the TaEXPB23 gene could enhance the drought resistance in tobacco plants (Li et al 2011). Gao et al (2008) demonstrated that the expression and activity of expansin proteins are induced under drought stress in wheat coleoptiles, suggesting the role of these proteins in response to water deficit circumstances (Gao et al 2008)

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Conclusion