INHERITANCE OF GUSA AND NEO GENES IN TRANSGENIC RICE

Inheritance of foreign genes neo and gusA in rice (Oryza sativa L. cv. IR54 and Radon) has been investigated in three different primary (T-0 ) transformants and their progeny plants. T-0 plants were obtained by co-transforming protoplasts from two different rice suspension culture s with the neomycin phosphotransferase II gene [neo or aph (3') II] an d the beta-glucuronidase gene (uidA or gusA) residing on separate chim eric plasmid constructs. The suspension cultures were derived from cal lus of immature embryos of indica variety IR54 and japonica variety Ra don. One transgenic line of Radon (AR2) contained nea driven by the Ca MV 35S promoter and gusA driven by the rice actin promoter. A second R adon line (R3) contained nea driven by the CaMV 35S promoter and gusA driven by a promoter of the rice tungro bacilliform virus. The third t ransgenic line, IR54-1, contained nea driven by the CaMV 35S promoter and gusA driven by the CaMV 35S. Inheritance of the transgenes in prog eny of the transgenic rice was investigated by Southern blot analysis and enzyme assays. Southern blot analysis of genomic DNA showed that, regardless of copy numbers of the transgenes in the plant genome and t he fact that the two transgenes resided on two different plasmids befo re transformation, the introduced gusA and nea genes were stably trans mitted from one generation to another and co-inherited together in tra nsgenic rice progeny plants derived from self-pollination. Analysis of GUS and NPT II activities in T-1 to T-2 plants provided evidence that inheritance of the gusA and neo genes was in a Mendelian fashion in o ne plant line (AR2), and in an irregular fashion in the two other plan t lines (R3 and IR54-1). Homozygous progeny plants expressing the gusA and neo genes were obtained in the T-2 generation of AR2, but the hom ozygous state was not found in the other two lines of transgenic rice.