A leader intron and 115-bp promoter region necessary for expression of the carnation S-adenosylmethionine decarboxylase gene in the pollen of transgenic tobacco.

The expression of CSDC9 encoding S-adenosylmethionine decarboxylase (SAMDC) is developmentally and spatially regulated in carnation. To examine the regulation of the SAMDC gene, we analyzed the spatial expression of CSDC9 with a 5′-flanking β-glucuronidase fusion in transgenic tobacco plants. GUS was strongly expressed in flower, pollen, stem and vein of cotyledons. Expression in both anther and stigma was under developmental control; analysis of a series of mutants with deletions of the 5′-flanking region demonstrated differential activation in petal, anther, stigma and pollen grains. All the major cis-regulatory elements required for pollen-specific transcription were located in the upstream region between −273 and −158. This region contains four putative elements related to gibberellin induction (pyrimidine boxes, TTTTTTCC and CCTTTT) and pollen-specific expression (GTGA and AGAAA). In addition, the first 5′-leader intron was necessary for tissue-specific expression.