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Plant and Cell Physiology Advance Access published online on March 19, 2006
Plant and Cell Physiology, doi:10.1093/pcp/pcj037
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Plant and Cell Physiology 2006 © The Japanese Society of Plant Physiologists (JSPP); all rights reserved.
Received February 17, 2006
Accepted March 16, 2006

Regular Paper

Effects of PII Deficiency on Expression of the Genes Involved in Ammonium Utilization in the Cyanobacterium Synechocystis sp. Strain PCC 6803

Nobuyuki Takatani 1 and Tatsuo Omata 1 *

1 Laboratory of Molecular Plant Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan

* To whom correspondence should be addressed.
Tatsuo Omata, E-mail: omata{at}agr.nagoya-u.ac.jp


  Abstract

The Synechocystis sp. strain PCC 6803 mutant deficient in PII protein (the glnB gene product) was found to express glutamine synthetase activity several times higher than the wild-type strain. There was no significant difference in nitrate reductase activity levels between the two strains and the nitrite reductase levels were somewhat lower in the mutant than in the wild-type strain. The higher glutamine synthetase activity in the mutant was ascribed to higher expression levels of the glutamine synthetase genes (glnA and glnN), which belong to the regulon controlled by NtcA, a Crp-family transcription regulator. Examination of the effects of PII deficiency on other NtcA-regulated genes revealed that the transcript levels of amt1 (encoding an ammonium permease) and gifB (encoding an inhibitor of glutamine synthetase) were increased, whereas that of gifA (a homologue of gifB, encoding another glutamine synthetase inhibitor) was decreased, with those of nirA, nrtC, icd, sigE (rpoD2-V), nblA, and ntcA, being unaffected. Unlike the Synechococcus elongatus strain PCC 7942, induction or repression of the NtcA-regulated genes proceeded normally in the PII-deficient mutant upon nitrogen depletion. The altered steady-state expression levels of glnA, glnN, amt1, gifA, and gifB in the PII-deficient mutant suggested that Synechocystis sp. strain PCC 6803 has a mechanism for regulation of the subset of the NtcA-regulated genes related directly to ammonium assimilation.

Keywords: Ammonium assimilation; Cyanobacterium; Gene regulation; Glutamine synthetase; PII protein; Synechocystis sp. strain PCC 6803.
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A. Ishii and Y. Hihara
An AbrB-Like Transcriptional Regulator, Sll0822, Is Essential for the Activation of Nitrogen-Regulated Genes in Synechocystis sp. PCC 6803
Plant Physiology, September 1, 2008; 148(1): 660 - 670.
[Abstract] [Full Text] [PDF]


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