Salt overly sensitive 1 (SOS1) gene expression can be regulated via Azospirillum brasilense Sp7 in wheat seedlings under saline condition

Hamid Reza Ghassemi,Abolghasem Esmaeili,Akbar Mostajeran

doi:10.14720/aas.2018.111.2.17

Abstract

Salinity stress reduces plant growth via failure of physiological processes mainly due to the abundance of Na+ ion. Salt overly sensitive (SOS) signaling pathway is considered as an important component of Na+/K+ homeostasis system in plants, especially under saline condition. Moreover, it is reported that wheat-Azospirillum associated has resulted in an enhanced salinity tolerance. To evaluate involvement of Azospirillum species in regulation of SOS signaling pathway, inoculated and none-inoculated wheat seedlings with Azospirillum brasilense Sp7 were grown for five days. Then uniform seedlings were transferred into saline hydroponic media with and without 200 mM NaCl. The relative expression of TaSOS1 of root, sheath, and blade as well as Na+/K+ ratio was measured after 6, 24 and 48 hours since inoculated and non-inoculated seedling were transferred to NaCl media. Simultaneously Ca, Fe, proline content, root and shoot dry mass and soluble sugars were measured at 72 hour after application of NaCl. Result showed that salinity increased TaSOS1 gene expression, Na+, prolin and Na+/K+ ratio but Ca and Fe were decreased in root and shoot of wheat seedlings. Although A. brasilense Sp7 could improve salinity tolerance in wheat via reduction of Na uptake and upregulation of TaSOS1 expression, but do not have any effect in sodium distribution within plant parts. Therefore, salinity could increase TaSOS1 expression in the root, sheath and blade and A. brasilense Sp7 also could reduce the adverse effect of salinity via addition of over expression of TaSOS1.

Highlights

Wheat like some other crops cannot tolerate salinity (Tiwari et al, 2010)
Standard strain of A. brasilense Sp7 was obtained from NCIMB Company, in Germany and cultured in an NFb liquid medium supplemented with NH4Cl (0.25 g l1) at 30 °C (Baldani & Döbereiner, 1980) in Erlenmeyer flasks for 48 h using a rotary shaker at 200 rpm
The results of this study show that the wheat plant inoculation with A. brasilense Sp7 has a significant effect on K+ accumulation under saline and non-saline conditions

Summary

Introduction

Wheat like some other crops cannot tolerate salinity (Tiwari et al, 2010). Salinity has inhibitory effects on wheat growth indexes such as root growth (Neumann, 1995), root/shoot ratio (El-Hendawy et al, 2005), and total dry matter (Pessarakli & Huber, 1991). The saline condition caused an increase in sodium in the root and shoot of plants (Xue et al, 2004), some osmoticum components such as proline, soluble sugars (Hamdia et al, 2004), as well as none-enzymatic Seedling’s dry mass and K+ content in the roots and shoots of wheat cultivars (Akbarimoghaddam et al, 2011; Lekshmy et al, 2013) and maize (Turan, 2008) decreased by increasing salinity. Yadav et al (2012) showed that over expression of SOS1 gene in transgenic tobacco caused a higher salt tolerance, elevated seed germination, addition of root and shoot length, less dry mass reduction, higher K+/Na+ ratio and more sugars relative to wild-type plants. It has been suggested that the SOS signaling pathway has an important role in ion (Na+ and K+) homeostasis and salt tolerance under saline condition

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Results