Using bioengineering approaches to express halophyte genes that enhance salt tolerance gene expression in tobacco

Abstract

Salinity is a major concern for the agricultural production sector. Salinity is common in soils in hot and arid parts of the world, which limits agriculture in these regions. Tobacco (Nicotiana tabacum) is a widely grown and essential commercial crop that is sensitive to moderate levels of salt stress. To produce salt-resistant tobacco plants, Agrobacterium tumefaciens-mediated transformation was used to overexpress genes from the halophytes, Spinacia oleracea Betaine Aldehyde Dehydrogenase (SpBADH), Mesembryanthemum crystallinum High Affinity Potassium transporter (McHKT1), Salsola soda Na⁺/ H⁺ antiporters (SsNHX1) and Atriplex hortensis Betaine Aldehyde Dehydrogenase (AhBADH). 

Seventy-six transgenic plants were isolated and evaluated for transgene expression and salt tolerance in vitro and in vivo, respectively. This study shows that transgenic tobacco overexpressing AhBADH6 and SpBADH5 were more salt tolerant at germination and seedling phases than wild-type tobacco. Transgenic plants survived exposure to 200 mM NaCl, while wild-type plants died after a week of treatment. The overexpression of AhBADH6 and SpBADH5 transgenic lines retained more chlorophyll and accumulated more proline as single gene transformants, and used enhanced osmoregulatory capability, which decreased the toxic impact of Na⁺.

Salt tolerance was assessed in Mesembryanthemum crystallinum, Salsola soda, Atriplex hortensis, and Spinacia oleracea at 0,100, 200, and 300 mM NaCl. These halophytes salt tolerance genes might help other crops to improve salt tolerance. Halophyte plants were treated with NaCl for4 weeks to evaluate survived. The results found that salt tolerance genes in halophytes after four weeks of salt exposure show similar impacts on halophytes plants. This studied plant growth and survival at NaCl concentrations of 0 to300 mM. Stress had similar effects on all four species, with no detrimental effects on development.

Salt had a substantial effect on all variables investigated. When compared to untransformed tobacco, transgenic plants carrying salt-tolerant transgenes all behaved considerably differently to salt stress. Notably, salt stress conditions had a substantial detrimental impact on biomass, plant shoot characteristics, and plant root development, as well as proline and chlorophyll levels in untreated control plants. However, as compared to wild-type plants, transgenic plants behaved differently to salt. Furthermore, compared to the other lines, AhBADH6 and SpBADH5 demonstrated a high degree of salt tolerance throughout the germination and seedling stages. As a result, these two lines might be employed to increase the development of plants grown in saline conditions. Together, these results show that halophyte salt tolerance genes have promising potential for improving salt tolerance in crops.