FIG. 5.

Primer extension analysis of hutU transcripts. The RNAs prepared from cells of P. syringae grown at 22 and 4°C were used for primer extension reactions in the presence of Moloney murine leukemia virus reverse transcriptase and [α-³²P]ATP, as described in Materials and Methods. The products were analyzed on a sequencing gel (8 M urea-6% polyacrylamide gel electrophoresis) in parallel with the sequencing reaction products (i.e., A, C, G, and T) carried out with the same primer. The major primer-extended products are marked by arrowheads. Note that the two longest primer-extended products were considered for analyzing the promoters in the present study (see Fig. 6). The 4°C specific longest product was found repeatedly absent in the 22°C RNA specific reactions. The shortest product (the lowermost arrow) was compatible with a putative ς ⁵⁴-specific promoter located in the upstream region of the hutU gene.