Open AccessNrrA Directly Regulates Expression of hetR during Heterocyst Differentiation in the Cyanobacterium Anabaena sp. Strain PCC 7120
Author(s) -
Shigeki Ehira,
Masayuki Ohmori
Publication year - 2006
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01314-06
Subject(s) - biology , heterocyst , anabaena , strain (injury) , microbiology and biotechnology , bacteria , cyanobacteria , genetics , anatomy
Heterocyst differentiation in the cyanobacteriumAnabaena sp. strain PCC 7120 requires NtcA, the global nitrogen regulator in cyanobacteria, and HetR, the master regulator of heterocyst differentiation. Expression ofhetR is upregulated by nitrogen deprivation, and its upregulation depends on NtcA. However, it has not yet been revealed how NtcA regulates the expression ofhetR . In the experiments presented here, it was confirmed that NrrA (All4312), a nitrogen-responsive response regulator, was required for the upregulation ofhetR . The use of the nitrogen-responsive transcription initiation sites (TISs) for thehetR gene depended upon NrrA. NrrA bound specifically to the region upstream of TISs located at positions −728 and −696 in vitro. Overexpression ofnrrA resulted in enhancedhetR expression and heterocyst formation. A molecular regulatory cascade is proposed whereby NtcA upregulates the expression ofnrrA upon limitation of combined nitrogen in the medium and then NrrA upregulates the expression ofhetR , leading to heterocyst differentiation.