GsGASA1 mediated root growth inhibition in response to chronic cold stress is marked by the accumulation of DELLAs

Low, but not freezing temperatures are a major factor limiting plant vegetative growth and development. It is not clear what signaling mechanism is used to limit plant growth in response to chronic low temperatures, thus it is important to continue to isolate and characterize genes whose activity/expression correlate well with cold responses. In this study, a novel GASA gene was isolated from Glycine soja and named GsGASA1. Quantitative real-time PCR analysis indicated that GsGASA1 expression responded to exogenous gibberellic acid (GA) and abscisic acid (ABA) treatments. Compared with wild-type plants under long-term cold treatment, the constitutive expression of GsGASA1 in transgenic Arabidopsis plants enhanced the inhibition of root elongation, while also increasing the transcript levels of RGL2 and RGL3, two of five DELLA genes in Arabidopsis. DELLA is a class of transcriptional regulators in GA signaling pathway restraining plant growth. Our results imply that GsGASA1 participates in chronic cold-induced root growth inhibition with the accumulation of DELLA genes. Lastly, a subcellular localization study using a yellow fluorescent protein (YFP) fusion protein indicated that GsGASA1 was localized to the plasma membrane, cytoplasm and nucleus.