VARIATION IN THE INHERITANCE OF EXPRESSION AMONG SUBCLONES FOR UNSELECTED (UIDA) AND SELECTED (BAR) TRANSGENES IN MAIZE (ZEA-MAYS L)

Variation in the inheritance of expression among subclones for an unse lected (uidA) and a selected (bar) transgene was analyzed in two indiv idual transformation events in maize. The unselectable gene (uidA) and the selectable gene (bar), on two separate plasmids, were transferred to maize (Hi-II derivative) by particle bombardment of embryogenic ca lli or suspension cells. A total of 188 fertile T1 plants were obtaine d from one transformant (transformation event BG which integrated uidA and bar). A total of 98 fertile T1 plants were obtained from a second transformant (transformation event B which integrated bar). Through s elf-pollination and/or cross-pollination in the greenhouse, approximat ely 10000 T2 progeny were obtained from event BG, and more than 1000 T 2 progeny were obtained from event B. Segregation of transgene express ion was analyzed statistically in a total of 2350 T2 progeny from 40 T 1 subclones of event BG and in 217 T2 progeny from six T1 subclones fr om event B. Variation in the inheritance of expression among subclones for the two transgenes (uidA and bar) was observed in the two transfo rmants. A significant difference was observed between the use of the f emale or male as the transgenic parent in the inheritance of expressio n for the two transgenes in event BG. No inheritance through the polle n was observed in two of four T1 subclones analyzed in event B. Co-exp ression analysis of event BG showed that both transgenes were co-expre ssed in 67.7% of the T2 plants which expressed at least one of the two transgenes. Of the T2 expressing plants, 30.4% expressed only bar, an d 1.9% expressed only uid A. Inactivation of the unselected (uidA) and the selected (bar) transgenes was observed in individual T2 plants.