A PLANT TRANSFORMATION VECTOR WITH A MINIMAL T-DNA-II - IRREGULAR INTEGRATION PATTERNS OF THE T-DNA IN THE PLANT GENOME

A minimal T-DNA binary vector was used for Agrobacterium-mediated tran sfer of a chimeric T4 lysozyme gene located next to the left border, a nd transgenic potato plants which expressed T4 lysozyme protein were i dentified and further analysed. Frequent rearrangements of T4, lysozym e transgenes were detected. A vector derivative containing two matrix associated regions (MARs) flanking its multiple cloning site was const ructed. In transgenic potato plants, reduced variability in gene expre ssion due to position effects was detected. When either the donor vect or contained MAR sequences, or when vector pPCV701 which contains a pB R322 fragment next to the left border were used, only relatively few r earrangements were observed. However, when the T4 lysozyme gene was dr iven by a CaMV 35S promoter modified by multiplied enhancer region car rying either 2 or 4 elements, frequent rearrangements were again obtai ned.