Limits...
Salt acclimation of cyanobacteria and their application in biotechnology.

Pade N, Hagemann M - Life (Basel) (2014)

Bottom Line: Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood.This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water.In addition, cyanobacterial salt resistance genes also can be applied to improve the salt tolerance of salt sensitive organisms, such as crop plants.

View Article: PubMed Central - PubMed

Affiliation: Institut für Biowissenschaften, Abteilung Pflanzenphysiologie, Universität Rostock, Albert-Einstein-Str. 3, D-18059 Rostock, Germany. nadin.pade@uni-rostock.de.

ABSTRACT
The long evolutionary history and photo-autotrophic lifestyle of cyanobacteria has allowed them to colonize almost all photic habitats on Earth, including environments with high or fluctuating salinity. Their basal salt acclimation strategy includes two principal reactions, the active export of ions and the accumulation of compatible solutes. Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood. Here, we briefly review recent advances in the identification of salt acclimation processes and the essential genes/proteins involved in acclimation to high salt. This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water. In addition, cyanobacterial salt resistance genes also can be applied to improve the salt tolerance of salt sensitive organisms, such as crop plants.

No MeSH data available.


Global changes in the gene expression of Synechocystis sp. PCC 6803 after the addition of 4% NaCl to cells grown in freshwater medium. (a) Genes induced to different levels (red spikes represent about 200 genes) are shown on the chromosome of Synechocystis. Genes coding for proteins of special functions are highlighted. (b) The dynamic changes in the expression of different groups of genes are displayed. Genes are grouped in classes that show maximum expression or repression at selected time points after the addition of 4% NaCl (data from reference 70).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4390839&req=5

life-05-00025-f003: Global changes in the gene expression of Synechocystis sp. PCC 6803 after the addition of 4% NaCl to cells grown in freshwater medium. (a) Genes induced to different levels (red spikes represent about 200 genes) are shown on the chromosome of Synechocystis. Genes coding for proteins of special functions are highlighted. (b) The dynamic changes in the expression of different groups of genes are displayed. Genes are grouped in classes that show maximum expression or repression at selected time points after the addition of 4% NaCl (data from reference 70).

Mentions: The term “omics” comprises technologies that focus on the collective characterization and quantification of pools of biological molecules to provide a valuable database for the molecular understanding of biological processes. Recently, transcriptomics and proteomics were applied to characterize global salt acclimation in several cyanobacterial strains including mutants. Transcriptomics was initially performed with DNA microarrays to investigate global gene expression changes in salt-stressed cells of the moderately halotolerant strain Synechocystis sp. PCC 6803 [70,87,88]. These studies revealed that 200–300 genes are up-regulated and about the same number is down-regulated after the addition of 4% NaCl (Figure 3). However, a time-series analysis showed that the majority of gene expression changes are rather transient. Particularly, genes showing an early response soon returned to the control expression level. Among the early responding genes, many code for proteins of unknown biological function. Only few genes stably remained at an enhanced expression level after long-term salt acclimation [70]. Many of the stable up-regulated genes code for proteins with a “meaningful” function regarding high salt acclimation. For example, genes that code for enzymes involved in the GG synthesis and transport belong to this group, but so do genes that code for general stress proteins known to stabilize protein structures as well those defending the cell against reactive oxygen species (ROS) such as sodB (Figure 3). In general, these datasets provided a comprehensive overview of the dynamic expression of all genes that are directly and indirectly involved in the cellular response of Synechocystis to salt stress conditions. Recently, the high-throughput sequencing of cDNA fragments (RNAseq) has become popular as a tool for transcriptomics. This technique not only allows quantification of transcripts but also provides information about transcriptional start sites, operon structures, and previously unannotated genes that code for small proteins or non-protein-coding (nc) RNAs, such as antisense RNAs or small regulatory RNAs. For Synechocystis sp. PCC 6803, RNAseq showed that nearly the same number of genes code for mRNAs as for ncRNAs, and the latter group of genes comprises some of the most highly expressed genes [89]. Moreover, these studies also revealed that the genome of cyanobacteria is highly dynamic because different growth conditions not only caused differential gene expression in terms of quantitative changes, it also revealed many new promoters and genes that became active only under specific environmental signals [63]. Regarding salt stress, the RNAseq approach was first applied to Synechococcus sp. PCC 7002 [90]. Synechococcus-cells treated at a rather high salinity of 1.5 M NaCl showed many gene expression changes, among them the accumulation of transcripts for genes coding for proteins involved in GG synthesis and transport, proteins for general stress response such as SodB, small high-light-induced proteins, flavoproteins, etc., as was previously found in salt-shocked Synechocystis sp. PCC 6803. However, some differences were reported as well. For example, genes coding for ion transport proteins were stably induced in salt-shocked cells of Synechococcus sp. PCC 7002 and those for subunits of the photosystem 1, which were increased in Synechocystis sp. PCC 6803 under salt conditions [91], were found at rather decreased expression levels [90].


Salt acclimation of cyanobacteria and their application in biotechnology.

Pade N, Hagemann M - Life (Basel) (2014)

Global changes in the gene expression of Synechocystis sp. PCC 6803 after the addition of 4% NaCl to cells grown in freshwater medium. (a) Genes induced to different levels (red spikes represent about 200 genes) are shown on the chromosome of Synechocystis. Genes coding for proteins of special functions are highlighted. (b) The dynamic changes in the expression of different groups of genes are displayed. Genes are grouped in classes that show maximum expression or repression at selected time points after the addition of 4% NaCl (data from reference 70).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390839&req=5

life-05-00025-f003: Global changes in the gene expression of Synechocystis sp. PCC 6803 after the addition of 4% NaCl to cells grown in freshwater medium. (a) Genes induced to different levels (red spikes represent about 200 genes) are shown on the chromosome of Synechocystis. Genes coding for proteins of special functions are highlighted. (b) The dynamic changes in the expression of different groups of genes are displayed. Genes are grouped in classes that show maximum expression or repression at selected time points after the addition of 4% NaCl (data from reference 70).
Mentions: The term “omics” comprises technologies that focus on the collective characterization and quantification of pools of biological molecules to provide a valuable database for the molecular understanding of biological processes. Recently, transcriptomics and proteomics were applied to characterize global salt acclimation in several cyanobacterial strains including mutants. Transcriptomics was initially performed with DNA microarrays to investigate global gene expression changes in salt-stressed cells of the moderately halotolerant strain Synechocystis sp. PCC 6803 [70,87,88]. These studies revealed that 200–300 genes are up-regulated and about the same number is down-regulated after the addition of 4% NaCl (Figure 3). However, a time-series analysis showed that the majority of gene expression changes are rather transient. Particularly, genes showing an early response soon returned to the control expression level. Among the early responding genes, many code for proteins of unknown biological function. Only few genes stably remained at an enhanced expression level after long-term salt acclimation [70]. Many of the stable up-regulated genes code for proteins with a “meaningful” function regarding high salt acclimation. For example, genes that code for enzymes involved in the GG synthesis and transport belong to this group, but so do genes that code for general stress proteins known to stabilize protein structures as well those defending the cell against reactive oxygen species (ROS) such as sodB (Figure 3). In general, these datasets provided a comprehensive overview of the dynamic expression of all genes that are directly and indirectly involved in the cellular response of Synechocystis to salt stress conditions. Recently, the high-throughput sequencing of cDNA fragments (RNAseq) has become popular as a tool for transcriptomics. This technique not only allows quantification of transcripts but also provides information about transcriptional start sites, operon structures, and previously unannotated genes that code for small proteins or non-protein-coding (nc) RNAs, such as antisense RNAs or small regulatory RNAs. For Synechocystis sp. PCC 6803, RNAseq showed that nearly the same number of genes code for mRNAs as for ncRNAs, and the latter group of genes comprises some of the most highly expressed genes [89]. Moreover, these studies also revealed that the genome of cyanobacteria is highly dynamic because different growth conditions not only caused differential gene expression in terms of quantitative changes, it also revealed many new promoters and genes that became active only under specific environmental signals [63]. Regarding salt stress, the RNAseq approach was first applied to Synechococcus sp. PCC 7002 [90]. Synechococcus-cells treated at a rather high salinity of 1.5 M NaCl showed many gene expression changes, among them the accumulation of transcripts for genes coding for proteins involved in GG synthesis and transport, proteins for general stress response such as SodB, small high-light-induced proteins, flavoproteins, etc., as was previously found in salt-shocked Synechocystis sp. PCC 6803. However, some differences were reported as well. For example, genes coding for ion transport proteins were stably induced in salt-shocked cells of Synechococcus sp. PCC 7002 and those for subunits of the photosystem 1, which were increased in Synechocystis sp. PCC 6803 under salt conditions [91], were found at rather decreased expression levels [90].

Bottom Line: Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood.This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water.In addition, cyanobacterial salt resistance genes also can be applied to improve the salt tolerance of salt sensitive organisms, such as crop plants.

View Article: PubMed Central - PubMed

Affiliation: Institut für Biowissenschaften, Abteilung Pflanzenphysiologie, Universität Rostock, Albert-Einstein-Str. 3, D-18059 Rostock, Germany. nadin.pade@uni-rostock.de.

ABSTRACT
The long evolutionary history and photo-autotrophic lifestyle of cyanobacteria has allowed them to colonize almost all photic habitats on Earth, including environments with high or fluctuating salinity. Their basal salt acclimation strategy includes two principal reactions, the active export of ions and the accumulation of compatible solutes. Cyanobacterial salt acclimation has been characterized in much detail using selected model cyanobacteria, but their salt sensing and regulatory mechanisms are less well understood. Here, we briefly review recent advances in the identification of salt acclimation processes and the essential genes/proteins involved in acclimation to high salt. This knowledge is of increasing importance because the necessary mass cultivation of cyanobacteria for future use in biotechnology will be performed in sea water. In addition, cyanobacterial salt resistance genes also can be applied to improve the salt tolerance of salt sensitive organisms, such as crop plants.

No MeSH data available.