cDNA sequence analysis and expression of two cold-regulated genes in soybean

Two cold-regulated cDNAs, src1 and src2, were isolated from chilling-treated seedlings of a chilling-tolerant soybean cultivar (Glycine max L. cv. Kitamusume) by differential screening. The level of src1 transcript rose after exposure to low or high temperatures (5, 15 and 40 degrees C), drought, wounding and infection from soybean mosaic virus (SMV). The deduced polypeptide (SRC1) from the src1 cDNA has 102 amino acids, is hydrophilic and has nine amino acid repeats rich in glutamic acid, histidine, lysine and glycine. SRC1 shares homology with a water-stress regulated protein of rice (WSI724), a cold-regulated protein of alfalfa (CAS15). The level of the src2 transcript rose only following exposure to 5 degrees C indicating that this gene is induced specifically by chilling. The cDNA of src2 predicted a polypeptide (SRC2) of 290 amino acids containing seven repeats of an amino acid sequence rich in proline, glycine, tyrosine and glutamine, and a hydrophobic region at the carboxy terminus that might bind to membranes. Transcript level of src2 at 5 degrees C continued to increase up to 48 h in a chilling tolerant cv. Kitamusume, while it reached maximum at 12 h and declined in a sensitive cv. Koganejiro. (C) 1997 Elsevier Science Ireland Ltd.