Isolation and characterization of a Pinus radiata lignin biosynthesis-related O-methyltransferase promoter

A putative promoter fragment of a Pinus radiata gene encoding a multi-functional O-methyltransferase (AEOMT) was isolated from genomic DNA. Sequence analysis revealed a number of putative cis elements, including AC-rich motifs common in promoters of genes related to the phenylpropanoid pathway. The isolated promoter was fused to the GUS reporter gene and its expression profile analyzed in transgenic tobacco and in transient transformation experiments with P. radiata embryogenic and xylogenic tissue. The promoter conferred weak expression in embryogenic tissue but caused strong GUS activity in both ray parenchyma cells and developing tracheary elements of xylem strips. Histochemical analysis in transgenic tobacco plants revealed that the AEOMT promoter induced GUS expression in cell types associated with lignification, such as developing vessels, phloem and wood fibers and xylem parenchyma as well as in non-lignifying phloem parenchyma. The isolated promoter was activated by challenge of the tissue with a fungal pathogen. Our results also indicate that the control of lignin-related gene expression is conserved and can be compared in evolutionarily distant species such as tobacco and pine.