The Soybean GmRACK1 Gene Plays a Role in Drought Tolerance at Vegetative Stages

The receptor for activated C kinase 1 (RACK1) is a versatile scaffold protein that binds to numerous proteins to regulate diverse cellular pathways in Arabidopsis. However, little is known about the function of RACK1 in soybean (Glycine max L.). Here, we show the expression profile and putative function of a soybean RACK1 (GmRACK1). The amino acid sequence of GmRACK1 had seven tryptophan-aspartic acid (WD) repeats, in which there were typical glycine-histidine (GH) and WD dipeptides. Real-time reverse transcription-polymerase chain reaction analysis showed that GmRACK1 was expressed at different levels in all tissues examined and strongly downregulated by abscisic acid and drought stress. We therefore constructed soybean GmRACK1 silenced (RNA interference, RNAi) and overexpressing plants. There were no obvious phenotypic differences between the transgenic seedlings and wild type under normal condition. However, the GmRACK1-RNAi lines showed significantly improved in drought stress tolerance while the overexpressing seedlings were hypersensitive to drought stress when compared to wild type in terms of plant survival rates after 10 days of drought. GmRACK1-RNAi plants were observed to be more sensitive to ABA when seeds germinated and root grew. Furthermore, an enzyme activity analysis indicated that the GmRACK1-RNAi plants had higher superoxide dismutase, peroxidase, and catalase activities but less malondialdehyde content and electrolyte leakage than those of wild type when the plants were exposed to dehydration treatment, indicating a better anti-oxidative stress capability and less membrane damage. This finding was consistent with the accumulation of reactive oxygen species (ROS) and lower expression of ROS-scavenging genes in the GmRACK1-OE lines. We conclude that the GmRACK1 gene plays an important role controlling ABA level and drought stress resistance in soybean.