Abstract
DREB transcription factors (TF) belong to the superfamily of AP2/ERF and their involvement in protein-protein interactions and DNA binding has been proposed. AP2/ERF proteins have important functions in the transcriptional regulation of a variety of biological processes related to growth and development, as well as various responses to environmental stimuli, regulating expression of plant biotic and abiotic stress-responsive genes. In this study an AP2/ERF TF gene (named RcDREB1) was isolated from castor bean (Ricinus communis L.) and its expression was analyzed in developing seeds, leaves, ovules, stems and petals of plants cultivated under field conditions. Transcripts were only observed in pollen grains, peaking during anthesis. The RcDREB1 deduced amino acid sequence was compared to other AP2/ERF TF proteins and presented 38–78% identity. Phylogenetic analysis classified it as a member of the CBF/DREB subfamily, rooting with the subgroup A-5. The RcDREB1 promoter was fused to the gus reporter gene and used to transform tobacco. Transgenic plants were exposed to various abiotic stress treatments (low and high tempera- tures, drought, salinity and exogenous ABA) and no detectable GUS expression was observed, suggesting that the RcDREB1 promoter is not active under tested conditions. In silico analyses revealed the presence of three copies of the regulatory late pollen-specific element (AGAAA) in the RcDREB1 5′-region. Interestingly, GUS expression was only observed in pollen grains, starting when the flower opened and initiating the senescence process; at this point, desiccated mature pollen grains are released from anthers. In addition, dehydrated developing pollen grains also expressed the gus gene. This is the first study on a DREB gene presenting pollen-specific expression.
Highlights
DREB transcription factors (TF) belong to the superfamily of APETALA2/Ethylene Responsive Factor (AP2/ERF) transcription factors
Some conserved motifs identified in the Arabidopsis and Glycine max ERF family proteins were observed in the deduced lined) were used to amplify the 5 ́ flanking region from the RcDREB1 by Polymerase Chain Reactions (PCRs)
ERFassociated amphiphilic repression (EAR) is protein preferentially transcribed in the vegeactivate/regulate the expression of a number a transcriptional regulatory motif identified in tative cell during pollen maturation
Summary
DREB transcription factors (TF) belong to the superfamily of AP2/ERF transcription factors. Each DREB/CBF protein contains a highly conserved APETALA2/Ethylene Responsive Factor (AP2/ERF) domain, which consists of 60 to 70 amino acids. The involvement of this domain in protein-protein interactions and DNA binding has been proposed.[1] In ERF the domain binds to the 11bp GCC box
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