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Transcriptome Analysis Reveals IsiA-Regulatory Mechanisms Underlying Iron Depletion and Oxidative-Stress Acclimation in Synechocystis sp. Strain PCC 6803.

ABSTRACT: Microorganisms in nature are commonly exposed to various stresses in parallel. The isiA gene encodes an iron stress-induced chlorophyll-binding protein which is significantly induced under iron starvation and oxidative stress. Acclimation of oxidative stress and iron deficiency was investigated using a regulatory mutant of the Synechocystis sp. strain PCC 6803. In this study, the ?isiA mutant grew more slowly in oxidative-stress and iron depletion conditions compared to the wild-type (WT) counterpart under the same conditions. Thus, we performed transcriptome sequencing (RNA-seq) analysis of the WT strain and the ?isiA mutant under double-stress conditions to obtain a comprehensive view of isiA-regulated genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed significant differences between the WT strain and ?isiA mutant, mainly related to photosynthesis and the iron-sulfur cluster. The deletion of isiA affects the expression of various genes that are involved in cellular processes and structures, such as photosynthesis, phycobilisome, and the proton-transporting ATPase complex. Weighted gene coexpression network analysis (WGCNA) demonstrated three functional modules in which the turquoise module was negatively correlated with superoxide dismutase (SOD) activity. Coexpression network analysis identified several hub genes of each module. Cotranscriptional PCR and reads coverage using the Integrative Genomics Viewer demonstrated that isiA, isiB, isiC, ssl0461, and dfp belonged to the isi operon. Three sRNAs related to oxidative stress were identified. This study enriches our knowledge of IsiA-regulatory mechanisms under iron deficiency and oxidative stress.IMPORTANCE This study analyzed the impact of isiA deletion on the transcriptomic profile of Synechocystis The isiA gene encodes an iron stress-induced chlorophyll-binding protein, which is significantly induced under iron starvation. The deletion of isiA affects the expression of various genes that are involved in photosynthesis and ABC transporters. WGCNA revealed three functional modules in which the blue module was correlated with oxidative stress. We further demonstrated that the isi operon contained the following five genes: isiA, isiB, isiC, ssl0461, and dfp by cotranscriptional PCR. Three sRNAs were identified that were related to oxidative stress. This study enhances our knowledge of IsiA-regulatory mechanisms under iron deficiency and oxidative stress.

SUBMITTER: Cheng Y

PROVIDER: S-EPMC7301839 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature

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Transcriptome Analysis Reveals IsiA-Regulatory Mechanisms Underlying Iron Depletion and Oxidative-Stress Acclimation in Synechocystis sp. Strain PCC 6803.

Cheng Yarui Y Zhang Tianyuan T Wang Li L Chen Wenli W

Applied and environmental microbiology 20200617 13

Microorganisms in nature are commonly exposed to various stresses in parallel. The isiA gene encodes an iron stress-induced chlorophyll-binding protein which is significantly induced under iron starvation and oxidative stress. Acclimation of oxidative stress and iron deficiency was investigated using a regulatory mutant of the Synechocystis sp. strain PCC 6803. In this study, the ΔisiA mutant grew more slowly in oxidative-stress and iron depletion conditions compared to the ...[more]

PMID: 32332138

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Project description:Cyanobacteria are foundational drivers of global nutrient cycling, with high intracellular iron (Fe) requirements. Fe is found at extremely low concentrations in aquatic systems, however, and the ways in which cyanobacteria take up Fe are largely unknown, especially the initial step in Fe transport across the outer membrane. Here, we identified one TonB protein and four TonB-dependent transporters (TBDTs) of the energy-requiring Fe acquisition system and six porins of the passive diffusion Fe uptake system in the model cyanobacterium Synechocystis sp. strain PCC 6803. The results experimentally demonstrated that TBDTs not only participated in organic ferri-siderophore uptake but also in inorganic free Fe (Fe') acquisition. 55Fe uptake rate measurements showed that a TBDT quadruple mutant acquired Fe at a lower rate than the wild type and lost nearly all ability to take up ferri-siderophores, indicating that TBDTs are critical for siderophore uptake. However, the mutant retained the ability to take up Fe' at 42% of the wild-type Fe' uptake rate, suggesting additional pathways of Fe' acquisition besides TBDTs, likely by porins. Mutations in four of the six porin-encoding genes produced a low-Fe-sensitive phenotype, while a mutation in all six genes was lethal to cell survival. These diverse outer membrane Fe uptake pathways reflect cyanobacterial evolution and adaptation under a range of Fe regimes across aquatic systems.IMPORTANCE Cyanobacteria are globally important primary producers and contribute about 25% of global CO2 fixation. Low Fe bioavailability in surface waters is thought to limit the primary productivity in as much as 40% of the global ocean. The Fe acquisition strategies that cyanobacteria have evolved to overcome Fe deficiency remain poorly characterized. We experimentally characterized the key players and the cooperative work mode of two Fe uptake pathways, including an active uptake pathway and a passive diffusion pathway in the model cyanobacterium Synechocystis sp. PCC 6803. Our finding proved that cyanobacteria use ferri-siderophore transporters to take up Fe', and they shed light on the adaptive mechanisms of cyanobacteria to cope with widespread Fe deficiency across aquatic environments.

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Dataset Information

Transcriptome Analysis Reveals IsiA-Regulatory Mechanisms Underlying Iron Depletion and Oxidative-Stress Acclimation in Synechocystis sp. Strain PCC 6803.

Publications

Transcriptome Analysis Reveals IsiA-Regulatory Mechanisms Underlying Iron Depletion and Oxidative-Stress Acclimation in <i>Synechocystis</i> sp. Strain PCC 6803.

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