REPORTER GENES AND HIGHLY REGULATED PROMOTERS AS TOOLS FOR TRANSFORMATION EXPERIMENTS IN VOLVOX-CARTERI

The multicellular alga Volvox is an attractive model for the study of developmental processes. With the recent report of successful transfor mation, regulated promoters as well as reporter genes working in this organism are now required. The Volvox genes encoding arylsulfatase and the extracellular glycoprotein ISG are strictly regulated. The former is transcribed only under conditions of sulfur starvation, whereas th e latter operates under extreme developmental control-i.e., it is tran scribed for only a few minutes in Volvox embryos at the stage of embry onic inversion. The gene encoding the sexual pheromone of Volvox carte ri was placed under the control of the arylsulfatase promoter. In resp onse to sulfur deprivation, V. carteri transformed by this construct s ynthesized and secreted biologically active pheromone. In addition, th e gene encoding Volvox arylsulfatase was placed under the control of t he ISG promoter. Transformed algae synthesized arylsulfatase mRNA only during embryonic inversion. These experiments demonstrate the usefuln ess of both the arylsulfatase and the sexual pheromone reporter genes. In addition, the highly regulated arylsulfatase promoter allows the c onstruction of inducible expression vectors for cloned genes.