Overexpression of Soybean (Glycine max (L.) Meer.) L34 Gene Leads to Reduced Survival to Cold Stress in Transgenic Arabidopsis

A ribosomal protein (R-protein) L34-like gene, designated as SOL34, was isolated from soybean using a cDNA-amplified fragment length polymorphism (cDNA-AFLP) approach. The full-length cDNA sequence of SOL34 was 360 bp, and encoding a protein with a calculated molecular mass of 132 kD. When compared to 60S ribosomal L34 proteins in Genbank using the blastp tool, the SOL34 had 95%, 95%, and 90% amino-acid-sequence identity with those in Medicago truncatula (gi|113205273|), Solanum demissum (gi|48057670|), and Arabidopsis thaliana (gi|2500376|), respectively. Accumulation of the transcriptional product in root tips at the four-leaf stage was about two- or fivefold higher than that of the embryonic axis and leaf. At the same time, SOL34 was responsive to low temperature, and demonstrated enhanced transcriptional levels in embryonic axes imbibed at 4°C for 12 h. However, these characteristics of SOL34 gene expression induced by low temperature were detected only in root tips and embryonic axes, but not in leaves. The SOL34 gene was then transferred into Arabidopsis in both sense and antisense orientations, under the control of the cauliflower mosaic virus (CaMV) 35S promoter for functional analysis. Transgenic plants overexpressing SOL34 were more sensitive to cold stress than wild-type plants; while transgenic plants carrying the antisense construct exhibited higher levels of resistance to freezing temperature than control plants. This suggested that SOL34 might play a ‘negative’ role in metabolic processes for adaptation of seeds to low-temperature stress during imbibition.