Enhanced salt tolerance of transgenic vegetable soybeans resulting from overexpression of a novel Δ1-pyrroline-5-carboxylate synthetase gene from Solanum torvum Swartz

Abstract

Vegetable soybeans [Glycine max (L.) Merrill] are susceptible to salt stress and, thus, soil salinity can severely affect their growth and productivity. To enhance the salt tolerance of vegetable soybeans, a novel Solanum torvum Swartz Δ1-pyrroline-5-carboxylate synthetase gene (StP5CS, GenBank accession number: JN606861) that encodes a critical regulatory enzyme in proline biosynthesis was transformed into the cultivar NY-1001 using an Agrobacterium-mediated transformation method. PCR and Southern blot analyses indicated that two independent T0 fertile transgenic plants were generated. The transgenic plants transmitted the transgenes into their T1 progeny in a 3:1 ratio. The T2 and T3 homozygous transgenic lines (HTLs) were examined for salt tolerance in pot and hydroponic cultures, respectively. The StP5CS overexpression conferred salt tolerance in T2 and T3 HTLs. Under NaCl stress conditions, the leaf scorch scores of T2 and T3 HTLs were significantly lower than those of wild-type (WT) plants. The plant height, leaf area, relative chlorophyll content, and number of fresh pods of T2 and T3 HTLs were significantly higher than those of WT plants. Compared with WT plants, T2 and T3 HTLs had significantly higher levels of proline and significantly lower levels of membrane lipid peroxidation. These results indicate that StP5CS overexpression in HTLs results in enhanced salt tolerance associated with higher levels of proline accumulation under salinity stress and that StP5CS can be utilized to improve salinity tolerance in vegetable crop genetic engineering.