Fig 1.

Primer extension analysis of the devB gene promoter region. Primer extension was carried out with primer alr3710-16 and RNA isolated from Anabaena sp. strain PCC 7120, strain CSE2 (ntcA), and strains DR884a and CSSC2 (hetR), grown in bubbled cultures with ammonium (0) and incubated in the absence of combined nitrogen for the indicated times (in hours). The positions of the −704 and −454 RNA 5′ ends are indicated. A sequence ladder of the same DNA region is shown at the right in panel C. WT, wild type.