Tissue-specific and wound-inducible pattern of expression of the mannopine synthase promoter is determined by the interaction between positive and negative cis-regulatory elements

In transgenic tobacco plants the regulatory region of the Agrobacterium genes involved in mannopine synthesis ( pmas ) directs expression in vascular tissues and is induced upon wounding. To identify cis -acting sequences required for the cell-type-specific and wound-inducible expression of this regulatory region, the expression pattern of chimeric genes in which 5' upstream deletions of the pmas1' promoter direct the expression of the β-glucuronidase coding sequence, was analyzed in transgenic tobacco plants. It was found that the pmas1' promoter is specifically expressed in phloem cells and that this tissue-specific pattern of expression is the result of the interaction of at least two negative regulatory elements with a positive element that directs expression in many cell types. It was also found that wound induction is mediated by two different mechanisms, one of them involving a dramatic change in tissue-specific expression.