A phospho-driven partner switch dictates heterocyst fate in the cyanobacterium Anabaena sp. PCC 7120

ABSTRACT: Here, we report a dedicated developmental PSS that controls heterocyst differentiation in the multicellular cyanobacterium Anabaena sp. PCC 7120. Bioinformatic analysis identified a gene cluster encoding the putative anti-sigma factor All2284 (NfsS), anti-anti-sigma factor All2283 (NfsR), and a phosphatase Alr2280 (NfsP). AlphaFold Multimer confirmed that NfsS and NfsR are structurally similar to sporulation homologs in B. subtilis and predicted a high-confidence complex between them. In vitro, NfsS phosphorylates NfsR on a conserved serine residue. Notably, a catalytic dead mutant of NfsS is unable to phosphorylate NfsR, confirming the kinase activity of NfsS. Bacterial two-hybrid and co-purification assays demonstrated that NfsS binds the developmental sigma factors SigC and SigE. Deletion of the nfsR or nfsP genes abolished heterocyst formation and prevented diazotrophic growth. Comparative RNA-seq of the ΔnfsR mutant and wild type revealed downregulation of heterocyst genes in the mutant. These included the nifHDK nitrogenase subunits encoding genes and the ferredoxin fdxH, consistent with the inability to sustain diazotrophic growth. Our findings establish a phosphorylation-dependent checkpoint that activates heterocyst-specific genes, thereby expanding the functional repertoire of partner-switch mechanisms from stress survival to programmed terminal cell differentiation. This SuperSeries contains the raw RNA-seq reads and processed count data from the wild-type and ΔnfsR mutant strains used in this study.

ORGANISM(S): Nostoc sp. PCC 7120 = FACHB-418

PROVIDER: GSE321668 | GEO | 2026/09/03

REPOSITORIES: GEO