The role of the ??LysR-type transcription factor PacR in regulating nitrogen metabolism in Anabaena sp. PCC7120

Deletion of the global transcription factor PacR in Anabaena triggers heterocyst formation even in NO3- containing medium, likely due to impaired NO3- uptake and disrupted NH4+ assimilation in the GOGAT cycle. This phenotype may be exacerbated by reduced PSI-yield and reduced expression of ferredoxin, which may lead to less reducing equivalents for nitrogen uptake and fixation. These results highlight PacR's role as a global regulator of carbon metabolism and photosynthesis while also establishing its involvement in regulating nitrogen metabolism. Overall design: To investigate the effect of PacR-deletion in Anabaena sp. PCC7120, we used a ?pacR strain and a control strain which expressed PacR. We took samples directly before changing the nitrogen source from NH4+ to NO3- as well as 1h after and 12h after the shift. RNA was extracted from 3 biological replicates per timepoint and strain. We then performed differential expression anaysis between the strains and between the timepoints for each strain.