Morphological, Physiological and Metabolomic Response of transgenic tobacco plants (N. tabacum L.) overexpressing GmGSTU4 under Drought Stress

Abstract

GSTs appear to have a significant role in plants’ adaptation under abiotic stress as many isoenzymes are found to be differentially expressed under these conditions yet, little is known about the regulatory functions of GSTs. Wild type and transgenic tobacco plants over-expressing the soybean GmGSTU4 of cultivars Basmas, Burley and Virginia were grown in vitro under 100 and 200mM mannitol or in soil (plant pots) by withholding watering for 15 days. However, GmGSTU4 plants did not exhibit significant differences in drought tolerance compared to wild-type plants. Morphological (shoot length, total and root fresh weight) and physiological (chlorophyll content, relative water content and photosynthetic capacity) parameters of transgenic plants did not differ from the wild-type in the presence of 100 or 200mM mannitol or in the soil when watering was halted. Metabolite profiling was used to understand the dynamics between the wild-type and transgenic tobacco response to drought stress. Different metabolic pathways are involved in production of osmoprotectants. These molecules accumulate in plants under stress conditions as adaptive mechanism, which can provide stress tolerance. GmGSTU4 plants did not exhibit difference in drought tolerance compared to wild-type plants, however metabolomics analysis indicated alterations in metabolite profile and increased concentration of sorbitol, glycerol and pyruvic acid. In conclusion, overexpression of GmGSTU4 in transgenic plants did not affect their drought stress tolerance although it has altered their metabolite profile possible because of diverse effects on plant stress tolerance mechanism.