A gene cluster that regulates both heterocyst differentiation and pattern formation in Anabaena sp. strain PCC 7120

Wei Zhang, Ye Du, Ivan Khudyakov, Qing Fan, Hong Gao, Degang Ning, C. Peter Wolk, Xudong Xu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

Wild-type Anabaena sp. strain PCC 7120, a filamentous nitrogen-fixing cyanobacterium, produces single heterocysts at semi-regular intervals. asr0100 (patU5) and alr0101 (patU3) are homologous to the 5′ and 3′ portions of patU of Nostoc punctiforme. alr0099 (hetZ) overlaps the 5′ end of patU5. hetZ, patU5 and patU3 were all upregulated, or expressed specifically, in proheterocysts and heterocysts. Mutants of hetZ showed delayed or no heterocyst differentiation. In contrast, a patU3 mutation produced a multiple contiguous heterocyst (Mch) phenotype and restored the formation of otherwise lost intercalary heterocysts in a patA background. Decreasing the expression of patU3 greatly increased the frequency of heterocysts in a mini-patS strain. Two promoter regions and two principal, corresponding transcripts were detected in the hetZ-patU5-patU3 region. Transcription of hetZ was upregulated in a hetZ mutant and downregulated in a patU3 mutant. When mutants hetZ::C.K2 and hetZ::Tn5-1087b were nitrogen-deprived, PhetC -gfp was very weakly expressed, and in hetZ::Tn5-1087b, PhetR-gfp was relatively strongly expressed in cells that had neither a regular pattern nor altered morphology. We conclude that the hetZ-patU5-patU3 cluster plays an important role in co-ordination of heterocyst differentiation and pattern formation. The presence of homologous clusters in filamentous genera without heterocysts is suggestive of a more general role.

Original languageEnglish (US)
Pages (from-to)1429-1443
Number of pages15
JournalMolecular Microbiology
Volume66
Issue number6
DOIs
StatePublished - Dec 2007

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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