Stability of lac operator arrays in Agrobacteriumtumefaciens strain GV3101/MP90. (a) Schematic map of the construct, restriction sites and probe sites. RB, right border; p35S, cauliflower mosaic virus 35S promoter, LacOs, 256mer of lac operator arrays; GVG, glucocorticoid-binding domain-VP16 acidic activation domain-Gal4 DNA-binding domain; TE9, pea rbcs-E9 terminator; pNOS, nopaline synthase gene (NOS) promoter; HPT, hygromycin phosphotransferase; TNOS, NOS terminator; 6×UAS, 6×Gal4 UAS; TATA, TATA box; T3A, pea rbcs-3A terminator; LB, left border. (b) Three independent Agrobacterium colonies transformed with the binary vector, pEL702 (25 kb) which contains LacOs were cultured for 2 days in liquid culture. The vectors were extracted and subjected to Southern blot analysis after PstI digestion, which releases the LacOs from the vector. The blotted membrane was hybridized with random primer-labeled 40× lac operator arrays (thick dashed line in (a)). Kb, kilobase pairs; M, 1 kb size marker.