In Fig 5, the bent arrow, which indicates the transcription start point, and ‘-272’ are positioned incorrectly in the sequence. The electrophoretogram of the 5′ RACE-PCR products of hetR transcripts in the wild type and the mutant is missing. Please see the correct Fig 5 here.

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Fig 5. Differences between Anabaena 7120 and the P_hetR-DIF1^- strain in heterocyst differentiation and expression of hetR.

(A) Photomicrographs of Anabaena 7120 and the P_hetR-DIF1^- strain at 24 h and 48 h after nitrogen stepdown. Frequencies of heterocysts/proheterocysts are indicated. (B) A stretch of sequence upstream of hetR, including the DIF1 motif, potential HetR-binding sequence and the tsp at -272 (left), and the electrophoretogram of the 5′ RACE-PCR products of hetR transcripts in the two strains at 18 h after nitrogen stepdown (right). Each band of the RACE-PCR (indicated with tsp) was confirmed by sequencing.

https://doi.org/10.1371/journal.pone.0269050.g001

Accordingly, the caption for Fig 5 has been updated to include updated information. Please see the complete, correct Fig 5 caption here.

In the Discussion, there is an error in the first two sentences of the third paragraph. The correct sentences are:

First, we showed that the DIF1-motif promoter is responsible for the upregulation of hetR in (pro)heterocysts. Substitutions at the DIF1 motif greatly reduced the transcription activity of P_hetR; a mutant of Anabaena 7120 with the DIF1 motif of hetR substituted in the genome showed no transcription from the tsp -272 (previously -271, the heterocyst-specific tsp in the wild type [47]).