The Arabidopsis thaliana dhdps gene encoding dihydrodipicolinate synthase,key enzyme of lysine biosynthesis, is expressed in a cell-specific manner

Lysine synthesis in prokaryotes, some phycomycetes and higher plants starts with the condensation of Laspartate-beta-semialdehyde (L-ASA) and pyruvate into dihydrodipicolinic acid. The enzyme that catalyses this step, dihydro dipicolinate synthase (DHDPS), is inhibited by the end-product lysine and i s therefore thought to have a regulatory control on lysine synthesis. We ha ve cloned and sequenced an Arabidopsis thaliana DNA fragment containing 900 bases upstream of the dhdps coding sequence. A transcriptional fusion of t his fragment with the beta-glucuronidase reporter gene (uidA, Gus) was used to study the transcription properties of this promoter fragment (DS). No l ysine-induced repression on transcription could be detected. Expression of DS-Gus activity in transformed Arabidopsis thaliana and Nicotiana tabacum w as found to be cell type-specific. In the vegetative parts of the plant, GU S activity was located in meristems and young vasculature of roots, in vasc ulature of stem and leaves and in the meristems of young shoots. In flowers , high expression was found in the carpels, style, stigma, developing embry os, tapetum of young anthers and pollen. We demonstrated that the Arabidops is DS promoter can direct its cell type-specific expression in a heterologo us plant, Nicotiana tabacum. The importance of transcriptional regulation o f the dhdps gene, and in more general genes involved in amino acid biosynth esis, is discussed.