Cloning and characterisation of an endosperm specific glutelin B1 promoter from Sri Lankan rice (Oryza sativa L. ssp. indica) variety Bg 250

Glutelins are the primary source of energy storage in the endosperm of rice grains. Among the glutelin promoters, Glutelin B-1 (GluB-1) is widely studied and used in transgenic rice plants to express recombinant proteins in the endosperm. In this study, three regions: 350 bp, 1308 bp and 2300 bp of the GluB-1 promoter were PCR amplified from the genomic DNA of Bg 250 rice variety. The amplified fragments were cloned into pGEM®-T Easy vector for characterisation of GluB-1 promoter. Each region of GluB-1 promoter was separately cloned into the promoterless binary vector pCAMBIA1391Z harbouring the β-glucuronidase (GUS) reporter gene. Putative transgenic plants were generated by Agrobacterium-mediated gene transformation and confirmed by PCR using nopaline synthase terminator primers. All GluB-1 promoter constructs showed expression of the GUS gene in the endosperm of T0 transgenic plant seeds. The 1308 bp GluB-1 promoter revealed the highest expression as determined by the GUS assay. This indicates the potential of this promoter for expression of recombinant proteins in rice endosperm.