Tissue-Specificity and Stress Responsiveness of the Promoter Region of a Gene Encoding an Alanine-Glyoxylate Aminotransferase from Eucalyptus grandis

The combination of modern biotechnology to conventional breeding techniques has an enormous potential to increase Eucalyptus productivity and stress tolerance. Among the molecular tools necessary for Eucalyptus improvement through the incorporation of transgenic techniques, the identification and characterization of organ-specific or stimulus-dependent promoters is a priority. In this context, the present study aimed to characterize the promoter region of a Eucalyptus grandis gene encoding an alanine-glyoxylate aminotransferase (EC 2.6.1.44). Firstly, the tissue-specificity of gene expression was validated in E. grandis using quantitative RT-qPCR. Subsequently, an expression cassette containing the 5’-upstream region (1050 bp) of the corresponding gene was fused to GUS and stably transformed in Arabidopsis thaliana Col-0 plants. Histochemical analyses of GUS activity revealed reporter expression mainly in the vascular tissues of leaves and roots. Analysis of the promoter sequence using the PlantCare database revealed several regulatory motifs related to hormone regulation and both abiotic and biotic stress responsiveness. Thus, promoter regulation in response to ABA (10 nm) and Pseudomonas syringae pv tomato inoculation was further investigated. The results obtained showed a down-regulation of GUS expression in response to ABA and P. synrigae.

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