Expression of a sesame geranylgeranyl reductase cDNA is induced by light but repressed by abscisic acid and ethylene

Geranylgeranyl reductase (chl p) is localized in plastids and catalyzes the reduction of geranylgeranyl diphosphate to phytyl diphosphate,a molecule required for both tocopherol and chlorophyll biosyntheses. to understand the regulation of chl p expression in sesame,a chl p cdna (sichlp) was isolated and the effects of light and phytohormones on sichl p expression was investigated. the putative sichlp cdna was 1,633 bp and included a 1,394 bp open reading frame encoding a polypeptide of 465 amino acid residues. sichl p mrna was expressed most abundantly in leaves and cotyledons,moderately in developing capsules and seeds,but little in flowers,hypocotyls and roots of healthy seedlings and plants. expression of sichl p in a cotyledon was induced by light,but the level of induction was higher in red light than in far-red or blue light. however,sichl p expression was diminished by dark,ethylene and abscisic acid.