DEVELOPMENTALLY-REGULATED EXPRESSION OF THE RICE CALMODULIN PROMOTER IN TRANSGENIC TOBACCO PLANTS

To study the expression of rice calmodulin genes (RCaM-1 and RCaM-2), rice calmodulin promoters were fused with reporter genes (CAT and GUS) and introduced into tobacco cells. The expression of chimeric rice Ca M promoter-cat gene in transgenic tobacco plants showed that both CaM promoters are expressed in all tissues tested, including the reproduct ive organs. However, RCaM-1 and RCaM-2 promoter activity had different ial levels of expression. RCaM-1 promoter is strongly expressed largel y in flowers and young seeds in comparison to other parts of transgeni c plants, whereas RCaM-2 promoter is strongly expressed in young petio les and stems in comparison to other parts of the transgenic plants. R CaM-2 promoter, which has a comparatively higher level of expression t han RCaM-1 promoter, was used to investigate the effects of auxin and light on calmodulin gene expression in transgenic plants. RCaM-2 promo ter activity was strongly increased with auxin-treatment, and was also slightly enhanced under dark conditions. The expression of RCaM-2 pro moter was remarkably induced with sucrose or salicylic acid treatment but not ethephon. Strong GUS staining was observed in meristemic tissu e such as stem apex, petiole and root tips. These results suggest that the calmodulin gene may play a vital role in the signal transduction process and cell growth.