Optimization of Agrobacterium pre-culture and infection media for efficient transient expression efficiency. Four-day-old Arabidopsis efr-1 seedlings infected with Agrobacterium C58C1(pTiB6S3ΔT)H carrying pBISN1 were grown in various pre-culture and co-cultivation media to test their effects on transient GUS expression efficiency measured by GUS staining and quantitative GUS activity. (A) Various pre-culture and infection media in the absence or presence of vir gene inducer AS at the indicated concentration. (B) Effect of factors in AB-MES medium on increased transient expression efficiency. (C) Effect of AB salts, pH and buffering systems on transient GUS expression efficiency. Data for relative quantitative GUS activity are mean ± SD of 3 independent experiments. Values significantly different from that infected by ABM50 (A) or condition 1 (B and C) are denoted (*P < 0.05, **P < 0.01, ***P < 0.005 by Student’s t test).