Characterization Of A Eukaryotic Translation Initiation Factor5A Homolog From Tamarix Androssowii

Plants are constantly subject various types of environmental stress such as drought, heavy metal and high salinity, during their growth and development. In order to maintain adequate growth in multifarious environments, they have evolved abstruse network of signaling at molecular, cellular, and system level.The eukaryotic translation initiation factor5A (eIF5A) promotes formation of the first peptide bond at the onset of protein synthesis. However, the function of eIF5A in plants is not well understood. Previous studies showed that eIF5A is involved in multiple biological processes in plants. In this study, we characterized the function of eIF5A (TaeIF5A1) from Tamarix androssowii. The main results are as follows:Expression patterns of TaelF5A1gene were investigated under abiotic stress and the exogenous application of ABA by real-time RT-PCR. Results showed that TaeIF5A1is a stress-responsive gene that functions in the abscisic acid (ABA) dependent signaling pathway.To investigate the spatial expression of TaeIF5A1, the35S promoter in pCAMBIA1301was replaced with the TaeIF5A1promoter to drive the β-glucuronidase (GUS) gene, and transgenic Arabidopsis plants harboring the ProTaeIF5A1::GUS transgene were analyzed using GUS staining. GUS staining analysis showed that the TaeIF5A1mainly expressed in the main roots, the tips of leaf teeth, veins and flowers.One W-box motif was found to exist in the promoter of TaeIF5A1. To study which gene can recognize this W-box, the three tandem copies of promoter sequence fragment containing W-box motif sequence were cloned into a pHIS2vector, and were screened with Tamarix cDNA library for a one-hybrid assay. we isolated two cDNAs encoding the WRKY transcription factor (TaWRKY) and AP2/ERF and B3domain-containing transcription factor (TaRAV) that specifically bind to the165bp and461bp promoter fragments of TaelF5A1, which contain the W-box. To investigate the interaction between W-box and the upstream regulatory factors, we mutated the W-box core motif,"TGAC" with "TGGC","TAAC" or "TTTT", they failed to bind each of the mutants. RT-PCR analysis revealed that the expression patterns of TaRAV, TaWRKY and TaeIF5A1shared similar expression patterns under ABA and osmotic stress conditions.The interactions between TaeIF5Al and other TaeIF proteins using the Yeast two-hybrid showed that TaeIF5A1could specifically interact with TaeIF5A4and form a heterodimeric complex.Transgenic yeast INVScl (pYES2-TaeIF5A1) expressing TaeIF5A1showed elevated protein levels combined with improved abiotic stresses tolerance.