Proteomic identification of an embryo-specific 1Cys-Prx promoter and analysis of its activity in transgenic rice

Proteomic analysis of a rice callus led to the identification of 10 abscisic acid (ABA)-induced proteins as putative products of the embryo-specific promoter candidates. 5′-flanking sequence of 1Cys-Prx, a highly-induced protein gene, was cloned and analyzed. The transcription initiation site of 1Cys-Prx maps 96 nucleotides upstream of the translation initiation codon and a TATA-box and putative seed-specific cis-acting elements, RYE and ABRE, are located 26, 115 and 124 bp upstream of the transcription site, respectively. β-glucuronidase (GUS) expression driven by the 1Cys-Prx promoters was strong in the embryo and aleurone layer and the activity reached up to 24.9 ± 3.3 and 40.5 ± 2.1 pmol (4 MU/min/μg protein) in transgenic rice seeds and calluses, respectively. The activity of the 1Cys-Prx promoters is much higher than that of the previously-identified embryo-specific promoters, and comparable to that of strong endosperm-specific promoters in rice. GUS expression driven by the 1Cys-Prx promoters has been increased by ABA treatment and rapidly induced by wounding in callus and at the leaf of the transgenic plants, respectively. Furthermore, ectopic expression of the GUS construct in Arabidopsis suggested that the 1Cys-Prx promoter also has strong activity in seeds of dicot plants.

► Strong tissue-specific promoters are required for recent biotechnology.
► Protein-enriched aleurone layer & embryo are biotechnologically important tissues.
► Most of identified seed-specific promoters belong to the endosperm-specific class.
► A strong embryo- and aleurone layer-specific 1Cys-Prx promoter has been identified.
► Its activity was highest among the reported embryo-specific promoters in rice.