STABLE TRANSFORMATION AND LONG-TERM EXPRESSION OF THE GUSA REPORTER GENE IN CALLUS LINES OF PERENNIAL RYEGRASS (LOLIUM-PERENNE L)

Stable transformation of perennial ryegrass (Lolium perenne L.) was ac hieved by biolistic bombardment of a non embryogenic cell suspension c ulture, using the hpt and gusA gene. The transformation yielded on the average 5 callus lines per bombardment (1.4 x 10(6) cells). Stable in tegration of the genes into the plant genome was demonstrated by South ern analysis of DNA, isolated from hygromycin-resistant callus lines. The gusA reporter gene, which was regulated by the constitutive promot er of the rice gene GOS2, was expressed in both transient and stable t ransformation assays, indicating that this promoter is suitable for ex pression of a transferred gene in perennial ryegrass. Long-term GUS ex pression was observed in ca. 40% of the callus lines, whereas the othe r callus lines showed instability after 6 months and 1 year of culture .