COMPARISON OF PROMOTERS AND SELECTABLE MARKER GENES FOR USE IN INDICARICE TRANSFORMATION

The effectiveness of different promoters for use in Indica rice transf ormation was compared. Plasmids encoding the Escherichia coli uidA (ga ls) gene under the control of CaMV 35S, Emu, Actl or Ubil promoters we re delivered into cell suspension cultures by particle bombardment. Tr ansient gene expression, 48 h after delivery, was greatest from plasmi ds utilising the constitutive promoters, Actl and Ubil. Gene expressio n in stably transformed tissue was examined by bombarding embryogenic Indica rice calli with a pUbil-gus plasmid and a plasmid containing ei ther the selectable marker gene, hph, which confers hygromycin resista nce, or bar, which confers resistance to the herbicide phosphinothrici n (BASTA) each under the control of the CaMV 35S, Emu, Actl or the Ubi l promoters. The bombarded calli were placed on the appropriate select ion media and stained for GUS activity at 1 day, 3 weeks and 5 weeks a fter shooting. Callus bombarded with the pUbil-hph or the pEmu-hph con structs gave a dramatic increase in the size of the GUS staining areas with time. No such increase in the size of GUS staining areas was obs erved in calli co-bombarded with pUbil-gus and any of the bar containi ng constructs. Co-bombardment of calli with either the pEmu-hph or pUb il-hph construct and a virus minor coat protein (cp) gene construct re sulted in many fertile transgenic Indica rice plants, containing one t o eight copies of both the hph and cp genes. These genes were stably i nherited by the T-1 generation.