University of Arkansas, Fayetteville Division of Agriculture


Genetic manipulation of crop plants, through breeding or transgenic approaches, for enhanced tolerance to abiotic stress holds great promise for improving yields and promoting new methods for sustainable agriculture. This study examines the potential role that genes of the soybean, Glycine max L., encoding elongation factor-1 alpha (EF-1α) and glyoxalase I (GlxI) might play in response to salt stress. Previous reports have suggested a possible function for both GlxI and EF-1α in conferring enhanced salt tolerance in other plant species. In addition to other possible mechanisms, salt tolerance in soybeans can be regulated by plant uptake and transport of chloride ions. Soybean lines that transfer chloride to their foliage from the soil are termed “includers” and are considered to be more susceptible to salt stress than their counterparts, “excluders” that do not transport chloride into their leaves. We used chloride “includers”, cv. Clark and Dare, and “excluders”, cv. Lee68 and S100, to compare gene expression responses and plant susceptibility to chloride salts. Mineral analysis of Clark and Lee68 cultivars by inductively coupled plasma mass spectrometry was performed to verify the differences in chloride uptake. In an optimized greenhouse screening procedure, the excluder cv. Lee68 demonstrated fewer visual symptoms of salt stress when treated with the same salt concentrations as the includer, cv. Clark. RNA blots showed the soybean genes encoding EF-1α and I GlxI were equally induced in both includers and excluders following treatment with NaCl or CaCl2 . Although transcript levels for EF-1α and GlxI are induced by salt treatments, transcript profiles do not differ between salt-tolerant and susceptible soybean cultivars. This suggests that the cultivars respond to salt stress in similar ways, but that these genes are not responsible for the differential phenotypes.