FIG. 3.
Mapping of the transcription start sites of the hrpY, popABC, and hrp transcription unit 2 and 3 promoters. (A) Primer extension products of the hrpY promoter. The sequence indicated is the antisense (bottom) strand. Asterisks indicate the transcription start sites of the two extension products. RT was done with RNA from the wild-type strain grown in minimal medium (lane 1), in the presence of Arabidopsis plant cells (lane 2), or in complete medium (lane 3). An ethidium bromide-stained denaturing agarose gel loaded with the samples of the total RNA extracts used for RT is inserted below the appropriate gel tracks. (B) Sequence alignment of the hrpY, popABC, and hrp transcription unit 2 and 3 promoters. The last adenine in each sequence (underlined) is the transcription start as determined by 5′-RACE-PCR (for hrpY, the transcription start corresponds to the longest primer extension product) and was used as the origin for numbering of the sequence ruler. Numbers to the right of sequences represent distances from the initiation codons. The gray shaded box shows the position of the −10 hexamer. Open boxes indicate the conserved direct repeats of the hrpII box.