T-DNA constructs created to combine promoterless GUS reporter vectors with different configurations and promoters to express selectable markers.

(A) Group of vectors constructed in head to tail orientation with selectable marker upstream of the GUS reporter. The selectable marker cassette is comprised of hygromycin phosphotransferase gene (hptII, 1026 bp, in gray box) driven by CaMV 35S (848 bp, a1), Nos (307 bp, a2) or tCUP1 (519 bp, a3) promoters and terminated by the same CaMV 35S terminator (225 bp). The β-glucuronidase reporter gene (GUS, 2053 bp, in blue box) with nopaline synthase (nos) terminator (268 bp) at the 3′ end near the T-DNA right border (RB). (B) Group of vectors constructed in head to head orientation with reversed selectable marker upstream of the GUS reporter. The selectable marker gene is differentially expressed by CaMV 35S (b1), Nos (b2) or tCUP1 (b3) promoters placed near the start codon of GUS reporter. (C) Group of vectors constructed in head to head orientation similar to B series vectors except that a 254 bp sequence (triangle) derived from pCAMBIA1300 was inserted to separate the GUS reporter and its adjacent inverted promoter used for hptII gene expression. (D) Group of vectors constructed in head to tail orientation with GUS reporter upstream of the selectable marker. The GUS reporter gene is stacked with ATG near the RB and nos terminator close to CaMV 35S (d1), Nos (d2) or tCUP1 (d3) promoters used for hptII gene expression.