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.
Osmotic stress causes water molecules to efflux from cells through the cytoplasmic membrane. This study reveals that targeted mutation of the aqpZ gene, encoding an aquaporin water channel protein, in the cyanobacterium Synechocystis sp. PCC 6803 prevents the osmotic shrinkage of cells, suggesting that it is the water channel rather than the lipid bilayer that is primarily responsible for water transition through the membrane of this organism. The observations suggest that the aquaporin-mediated shrinkage of the Synechocystis cells plays an important role in changes of gene expression in response to hyperosmotic stress.
Cells of the cyanobacterium Synechocystis sp. PCC 6803 are equipped with a mechanosensitive ion channel MscL that is located in their plasma membrane. However, the exact function of the channel in this freshwater cyanobacterium is unknown.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.