Schematic illustration of Bxb1 recombinase-mediated transgene autoexcision in pollen. (a) T-DNA of the vector pMBXS824. PCR primers are indicated as r3&r4, b1&b2, g1&g2, e3&e4, and c1&c2 (Table 3), att sites as grey arrows and hybridization probes as grey rectangles. (b) Predicted pollen-specific autoexcision event and T-DNA fragments. POsPS3 drives the bxbNom gene expression during pollen development and POsPS1 drives the gusAeGFP gene expression after autoexcision. Abbreviations: POsPS1 and POsPS3, pollen specific promoters; bxbNom, optimized Bxb1 recombinase gene; P, PstI restriction site; other abbreviations are the same as in Figure 1.