FIG. 1.

RT-PCR analysis of the expression of the alr0484-alr0489 gene cluster. (A) The gene cluster and Anabaena ORF names (19) are depicted. (B) Retrotranscription was carried out with oligonucleotide primer RT-1 or RT-2 (initial positions indicated by the start of the corresponding arrow) and with RNA isolated from bubbled ammonium-grown cultures incubated for 6 h in the absence of combined nitrogen. The positions of the primers used for amplification correspond to the ends of the segments indicated in panel A, which are depicted in black, indicating amplification by RT-PCR, or in gray, indicating no amplification. + or −, RNA samples subjected or not to retrotranscription; g, total genomic DNA used as the template for amplification with the corresponding primers.