A Two-Component Mn²⁺-Sensing System Negatively Regulates Expression of the mntCAB Operon in Synechocystis

Abstract

Mn is an essential component of the oxygen-evolving machinery of photosynthesis and is an essential cofactor of several important enzymes, such as Mn-superoxide dismutase and Mn-catalase. The availability of Mn in the environment varies, and little is known about the mechanisms for maintaining cytoplasmic Mn(2+) ion homeostasis. Using a DNA microarray, we screened knockout libraries of His kinases and response regulators of Synechocystis sp PCC 6803 to identify possible participants in this process. We identified a His kinase, ManS, which might sense the extracellular concentration of Mn(2+) ions, and a response regulator, ManR, which might regulate the expression of the mntCAB operon for the ABC-type transporter of Mn(2+) ions. Furthermore, analysis with the DNA microarray and by reverse transcription PCR suggested that ManS produces a signal that activates ManR, which represses the expression of the mntCAB operon. At low concentrations of Mn(2+) ions, ManS does not generate a signal, with resulting inactivation of ManR and subsequent expression of the mntCAB operon.

The Histidine Kinase Hik34 Is Involved in Thermotolerance by Regulating the Expression of Heat Shock Genes in Synechocystis

“…We only found clear changes in gene expression in DHik27 and DHik34 cells. In DHik27 cells, as we published previously, expression of the mntCAB operon that encodes an ATP-binding cassette-type Mn 21 transporter was enhanced (Yamaguchi et al, 2002). By contrast, in DHik34 cells, the level of the transcript of the heat shock gene htpG was approximately 3-fold higher than that in wild-type cells ( Fig.…”

“…The plasmid with the spectinomycin-resistance gene cassette within the cloned hik34 gene fragment was used to transform Synechocystis cells (Williams, 1988). Spectinomycin-resistant colonies were isolated and cells with a fully segregated mutation were obtained after growth for several generations in BG-11 media that contained the antibiotic, as previously reported (Suzuki, et al, 2000Yamaguchi et al, 2002).…”

“…Then the hik34 coding sequence, linked to the promoter of the nrtA gene, was isolated by cleavage with NheI and XhoI and cloned into pVZ321 that had been digested with XbaI and XhoI. The resultant plasmids, namely, pVZ::hik34 and pVZ::pnrtA-hik34, and the original plasmid, pVZ321, were introduced into Synechocystis cells via triparental conjugation, as described previously (Zinchenko et al, 1999;Yamaguchi et al, 2002) and transformants were selected with resistance to chloramphenicol as the selectable marker.…”

“…PCC 6803 (hereafter Synechocystis) is an aquatic photoautotrophic prokaryote that has been used extensively for studies of genome-wide responses to stress Kanesaki et al, 2002;Inaba et al, 2003). These studies have led to the identification of specific His kinases (Hiks) and response regulators (Rres) that are involved in the perception and transduction of signals due to low temperature, salt stress, osmotic stress, and metal ion deficiency Yamaguchi et al, 2002;Marin et al, 2003;Paithoonrangsarid et al, 2004).…”

“…The chromosome of Synechocystis includes 44 putative genes for Hiks that are candidates for sensors of environmental signals Mizuno et al, 1996). It has already been demonstrated that the Hiks in Synechocystis are involved in the perception and transduction of signals due to cold stress (Suzuki et al, 2000, phosphate deprivation (Hirani et al, 2001;Suzuki et al, 2004), high osmolarity Paithoonrangsarid et al, 2004), heavy metal ions (Ló pez-Maury et al, 2002;Ogawa et al, 2002;Yamaguchi et al, 2002), and high concentrations of NaCl (Marin et al, 2003). In this article, we provide evidence that Hik34, one of the 44 putative Hiks in Synechocystis, is involved in the control of the expression of heat shock genes and the regulation of thermotolerance in Synechocystis.…”