Molecular cloning, characterization, and stress-responsive expression of genes encoding glycine-rich RNA-binding proteins in Camelina sativa L.

Abstract

Camelina sativa L. is an oil-seed crop that has potential for biofuel applications. Although the importance of C.sativa as a biofuel crop has increased in recent years, reports demonstrating the stress responsiveness of C.sativa and characterizing the genes involved in stress response of C.sativa have never been published. Here, we isolated and characterized three genes encoding glycine-rich RNA-binding proteins (GRPs) from camelina: CsGRP2a, CsGRP2b, and CsGRP2c. The three CsGRP2 proteins were very similar in amino acid sequence and contained a well-conserved RNA-recognition motif at the N-terminal region and glycine-rich domain at the C-terminal region. To understand the functional roles of CsGRP2s under stress conditions, we investigated the expression patterns of CsGRP2s under various environmental stress conditions. The expressions of the three CsGRP2s were highly up-regulated under cold stress. The expression of CsGRP2a was up-regulated under salt or dehydration stress, whereas the transcript levels of CsGRP2b and CsGRP2c were decreased under salt or dehydration stress conditions. The three CsGRP2s had the ability to complement cold-sensitive Escherichia coli mutants at low temperatures and harbored transcription anti-termination and nucleic acid-melting activities, indicating that the CsGRP2s possess RNA chaperone activity. The CsGRP2a protein was localized to both the nucleus and the cytoplasm. Expression of CsGRP2a in cold-sensitive Arabidopsis grp7 mutant plants resulted in decreased electrolyte leakage at freezing temperatures. Collectively, these results suggest that the stress-responsive CsGRP2s play a role as an RNA chaperone during the stress adaptation process in camelina.