摘要:
Cyanobacteria are globally important primary producers and nitrogen fixers. They are frequently limited by iron bioavailability in natural environments which often fluctuate due to rapid consumption and irregular influx of external Fe. Here we identify a succession of physiological changes in Synechocystis sp. PCC 6803 occurring over 14-16 days of iron deprivation and subsequent recovery. We observe several adaptive strategies which allow cells to push their metabolic limits under the restriction of declining intracellular Fe quotas. Interestingly, cyanobacterial populations exposed to prolonged iron deprivation showed discernible heterogeneity in cellular auto-fluorescence during the recovery process. Using FACS and microscopy techniques we revealed that only cells with high auto-fluorescence were able to grow and reconstitute thylakoid membranes. We propose that ROS mediated damage is likely to be associated with the emergence of the two subpopulations, and, indeed, a rapid increase in intracellular ROS content was observed during the first hours following iron addition to Fe-starved cultures. These results suggest that an increasing iron supply is a double-edged sword - posing both an opportunity and a risk. Therefore, phenotypic heterogeneity within populations is crucial for the survival and proliferation of organisms facing iron fluctuations within natural environments. This article is protected by copyright. All rights reserved.
作者机构:
[Qiu, Bao-Sheng; Yu, Qi; Zhang, Zhong-Chun; Wang, Miao-Yu] Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Yu, Qi; Zhang, Zhong-Chun; Wang, Miao-Yu] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.;[Schroeder, Julian I.; Scavo, Alexander; Yu, Qi] Univ Calif San Diego, Div Biol Sci, Cell & Dev Biol Sect, La Jolla, CA 92093 USA.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.
摘要:
Main conclusionCadmium-sensitive yeast screening resulted in the isolation of protein translation factorSaeIF1 from the hyperaccumulatorSedum alfredii which has both general and special regulatory roles in controlling cadmium accumulation.AbstractThe hyperaccumulator of Sedum alfredii has the extraordinary ability to hyperaccumulate cadmium (Cd) in shoots. To investigate its underlying molecular mechanisms of Cd hyperaccumulation, a cDNA library was generated from leaf tissues of S. alfredii. SaeIF1, belonging to the eukaryotic protein translation factor SUI1 family, was identified by screening Cd-sensitive yeast transformants with this library. The full-length cDNA of SaeIF1 has 582 bp and encodes a predicted protein with 120 amino acids. Transient expression assays showed subcellular localization of SaeIF1 in the cytoplasm. SaeIF1 was constitutively and highly expressed in roots and shoots of the hyperaccumulator of S. alfredii, while its transcript levels showed over 100-fold higher expression in the hyperaccumulator of S. alfredii relative to the tissues of a nonhyperaccumulating ecotype of S. alfredii. However, the overexpression of SaeIF1 in yeast cells increased Cd accumulation, but conferred more Cd sensitivity. Transgenic Arabidopsis thaliana expressing SaeIF1 accumulated more Cd in roots and shoots without changes in the ratio of Cd content in shoots and roots, but were more sensitive to Cd stress than wild type. Both special and general roles of SaeIF1 in Cd uptake, transportation, and detoxification are discussed, and might be responsible for the hyperaccumulation characteristics of S. alfredii.
作者机构:
[Qiu, Bao-Sheng; Qiu, Guo-Wei; Jiang, Hai-Bo; Shang, Jin-Long; Li, Zheng-Ke; Deng, Bin; Sun, Chuan-Yu] Cent China Normal Univ, Sch Life Sci, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Peoples R China.;[Lis, Hagar; Keren, Nir] Hebrew Univ Jerusalem, Alexander Silberman Inst Life Sci, Dept Plant & Environm Sci, Edmond J Safra Campus, Jerusalem, Israel.
通讯机构:
[Qiu, Bao-Sheng] C;[Keren, Nir] H;Cent China Normal Univ, Sch Life Sci, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Peoples R China.;Hebrew Univ Jerusalem, Alexander Silberman Inst Life Sci, Dept Plant & Environm Sci, Edmond J Safra Campus, Jerusalem, Israel.
摘要:
Cyanobacteria are globally important primary producers and nitrogen fixers with high iron demands. Low ambient dissolved iron concentrations in many aquatic environments mean that these organisms must maintain sufficient and selective transport of iron into the cell. However, the nature of iron transport pathways through the cyanobacterial outer membrane remains obscure. Here we present multiple lines of experimental evidence that collectively support the existence of a novel class of substrate-selective iron porin, Slr1908, in the outer membrane of the cyanobacterium Synechocystis sp. PCC 6803. Elemental composition analysis and short-term iron uptake assays with mutants in Slr1908 reveal that this protein is primarily involved in inorganic iron uptake and contributes less to the accumulation of other metals. Homologues of Slr1908 are widely distributed in both freshwater and marine cyanobacteria, most notably in unicellular marine diazotrophs. Complementary experiments with a homologue of Slr1908 in Synechococcus sp. PCC 7002 restored the phenotype of Synechocystis knockdown mutants, showing that this siderophore producing species also possesses a porin with a similar function in Fe transport. The involvement of a substrate-selective porins in iron uptake may allow cyanobacteria to tightly control iron flux into the cell, particularly in environments where iron concentrations fluctuate.
作者机构:
[Qiu, Bao-Sheng; Shang, Jin-Long; Shi, Huazhong; Ye, De-Min; Xu, Hai-Feng; Dai, Guo-Zheng; Song, Wei-Yu] Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Shang, Jin-Long; Shi, Huazhong; Ye, De-Min; Xu, Hai-Feng; Dai, Guo-Zheng; Song, Wei-Yu] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.;[Shi, Huazhong] Texas Tech Univ, Dept Chem & Biochem, Lubbock, TX 79409 USA.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.
作者机构:
[Qiu, Bao-Sheng; Li, Zheng-Ke; Dai, Guo-Zheng] Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Li, Zheng-Ke; Dai, Guo-Zheng] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.;[Zhang, Yong] Fujian Normal Univ, Coll Environm Sci & Engn, Fuzhou 350007, Fujian, Peoples R China.;[Xu, Kui] Sun Yat Sen Univ, Environm Microbi Res Ctr, Sch Environm Sci & Engn, Guangzhou 510006, Guangdong, Peoples R China.;[Bretherton, Laura; Finkel, Zoe, V] Dalhousie Univ, Dept Oceanog, Halifax, NS B3H 4R2, Canada.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.
摘要:
<jats:p>The poorly understood filamentous cyanobacterium <jats:italic>Pseudanabaena</jats:italic> is commonly epiphytic on <jats:italic>Microcystis</jats:italic> colonies and their abundances are often highly correlated during blooms. The response and adaptation of <jats:italic>Microcystis</jats:italic> to iron limitation have been extensively studied, but the strategies <jats:italic>Pseudanabaena</jats:italic> uses to respond to iron limitation are largely unknown. Here, physiological responses to iron limitation were compared between one <jats:italic>Pseudanabaena</jats:italic> and two <jats:italic>Microcystis</jats:italic> strains grown under different light intensities. The results showed that low‐intensity light exacerbated, but high‐intensity light alleviated, the negative effect of iron limitation on <jats:italic>Pseudanabaena</jats:italic> growth relative to two <jats:italic>Microcystis</jats:italic> strains. It was found that robust light‐harvesting and photosynthetic efficiency allowed adaptation of <jats:italic>Pseudanabaena</jats:italic> to low light availability relative to two <jats:italic>Microcystis</jats:italic> strains only during iron sufficiency. The results also indicated that a larger investment in the photosynthetic antenna probably contributed to light/iron co‐limitation of <jats:italic>Pseudanabaena</jats:italic> relative to two <jats:italic>Microcystis</jats:italic> strains under both light and iron limitation. Furthermore, the lower antenna pigments/chlorophyll <jats:italic>a</jats:italic> ratio and photosynthetic efficiency, and higher nonphotochemical quenching and saturation irradiance provided <jats:italic>Pseudanabaena</jats:italic> photoadaptation and photoprotection advantages over the two <jats:italic>Microcystis</jats:italic> strains under the high‐light condition. The lower investment in antenna pigments of <jats:italic>Pseudanabaena</jats:italic> than the two <jats:italic>Microcystis</jats:italic> strains under high‐light intensity is likely an efficient strategy for both saving iron quotas and decreasing photosensitivity. Therefore, when compared with <jats:italic>Microcystis</jats:italic>, the high plasticity of antenna pigments, along with the excellent photoadaptation and photoprotection ability of <jats:italic>Pseudanabaena</jats:italic>, probably ensures its ecological success under iron limitation when light is sufficient.</jats:p>
作者机构:
[Qiu, Bao-Sheng; Xu, Hai-Feng; Dai, Guo-Zheng] Cent China Normal Univ, Sch Life Sci, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Sch Life Sci, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.
摘要:
The subaerial cyanobacterium Nostoc flagelliforme can survive for years in the desiccated state and light exposure may stimulate photosynthetic recovery during rehydration. However, the influence of light quality on photosynthetic recovery and the underlying mechanism remain unresolved. Exposure of field collected N. flagelliforme to light intensity >/=2 mumol photons m(-2) s(-1) showed that the speed of photosystem II (PSII) recovery was in the following order: red > green > blue approximately violet light. Decreasing the light intensity showed that weak red light stimulated PSII recovery during rehydration. The chlorophyll fluorescence transient and oxygen evolution activity indicated that the oxygen evolution complex (OEC) was the activated site triggered by weak red light. The damaged D1 protein accumulated in the thylakoid membrane during dehydration and is degraded and resynthesized during dark rehydration. PsbO interaction with the thylakoid membrane was induced by weak red light. Thus, weak red light plays an important role in triggering OEC photoactivation and the formation of functional PSII during rehydration. In its arid habitats, weak red light could stimulate the awakening of dormant N. flagelliforme after absorbing water from nighttime dew or rain to maximize growth during the early daylight hours of the dry season.
摘要:
The mechanisms of cadmium toxicity to cyanobacterial photosynthesis have been extensively studied, but the response mechanisms to combinations of different cadmium concentrations and different light intensities are not yet well understood. The two principal objectives of the present work were to: 1) study the short term (5 h) toxic effects of cadmium on Synechocystis PCC6803 under three different culturing light intensity conditions; and, 2) investigate the effects of light history on Cd toxicity to Synechocystis. The maximal (capital EF, CyrillicM) and operational (capital EF, Cyrillic'M) photosystem II quantum yields, photosystem I quantum yield [Y (I)], cyclic electron flow, relative photochemical quenching (qPrel), relative non-photochemical quenching (qNrel), relative unquenched fluorescence (UQFrel), pigment contents, and cadmium uptake were evaluated when Synechocystis cells were treated with cadmium for 5 h under three different light conditions. We demonstrated that cadmium toxicity was enhanced with increasing growth light intensities due to increased cadmium uptake under higher light exposures, and the photoprotective mechanisms could not cope with cadmium and light stress under high light conditions. We also investigated Cd toxicity to Synechocystis adapted to three growth light intensities and subsequently shifted to different light intensity conditions to compare the effects of light regime shift on cadmium toxicity. We observed increased cadmium toxicity when the cells were transferred from low light to high light conditions. Interestingly, Synechocystis cells grown at high light intensities were more tolerant to cadmium than cells grown at low light intensities after the same light regime shift, due to the development of photoprotective mechanisms.
作者机构:
[Qiu, Bao-Sheng; Yang, Yi-Wen; Shang, Jin-Long; Jiang, Hai-Bo; Dai, Guo-Zheng; Zhang, Zhong-Chun] Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Yang, Yi-Wen; Shang, Jin-Long; Jiang, Hai-Bo; Dai, Guo-Zheng; Zhang, Zhong-Chun] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.;[Chen, Min] Univ Sydney, Sch Life & Environm Sci, Sydney, NSW 2006, Australia.;[Hou, Shengwei; Hess, Wolfgang R.] Univ Freiburg, Inst Biol 3, Fac Biol, Genet & Expt Bioinformat, D-79104 Freiburg, Germany.;[Li, Tao; Li, Qi] Chinese Acad Sci, Inst Hydrobiol, Key Lab Algal Biol, Wuhan 430072, Hubei, Peoples R China.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.
作者机构:
[Qiu, Bao-Sheng; Yang, Yi-Wen; Shang, Jin-Long; Huang, Da; Li, Zheng-Ke; Yin, Yan-Chao] Cent China Normal Univ, Sch Life Sci, Wuhan, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Yang, Yi-Wen; Shang, Jin-Long; Huang, Da; Li, Zheng-Ke; Yin, Yan-Chao] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Hubei, Peoples R China.;[Chen, Min] Univ Sydney, ARC Ctr Excellence Translat Photosynth, Sydney, NSW 2006, Australia.;[Chen, Min] Univ Sydney, Sch Life & Environm Sci, Sydney, NSW 2006, Australia.
通讯机构:
[Qiu, Bao-Sheng] C;[Chen, Min] U;Cent China Normal Univ, Sch Life Sci, Wuhan, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Hubei, Peoples R China.;Univ Sydney, ARC Ctr Excellence Translat Photosynth, Sydney, NSW 2006, Australia.
关键词:
Canthaxanthin;Desiccation;Helical carotenoid protein;Nostoc flagelliforme;Orange carotenoid protein;Red carotenoid protein
摘要:
The remarkable drought-resistance of the terrestrial cyanobacterium Nostoc flagelliforme (N. flagelliforme) has attracted attention for many years. In this study, we purified a group of red proteins that accumulate in dried field samples of N. flagelliforme. These red proteins contain canthaxanthin as the bound chromophore. Native-PAGE analysis revealed that the purified red proteins resolved into six visible red bands and were composed of four helical carotenoid proteins (HCPs), HCP1, HCP2, HCP3, and HCP6 (homologs to the N-terminal domain of the orange carotenoid protein (OCP)). Seven genes encode homologs of the OCP in the genome of N. flagelliforme: two full-length ocp genes (ocpx1 and ocpx2), four N-terminal domain hcp genes (hcp1, hcp2, hcp3, and hcp6), and one C-terminal domain ccp gene. The expression levels of hcp1, hcp2, and hcp6 were highly dependent on the water status of field N. flagelliforme samples, being downregulated during rehydration and upregulated during subsequent dehydration. Transcripts of ocpx2 were dominant in the dried field samples, which we confirmed by detecting the presence of OCPx2-derived peptides in the purified red proteins. The results shed light on the relationship between carotenoid-binding proteins and the desiccation resistance of terrestrial cyanobacteria, and the physiological functions of carotenoid-binding protein complexes in relation to desiccation are discussed.
作者机构:
[Qiu, Bao-Sheng; Qiu, Guo-Wei; Jiang, HB; Jiang, Hai-Bo; Zang, Sha-Sha; Lou, Wen-Jing; Li, Ding-Lan; Li, Zheng-Ke; Sun, Chuan-Yu] Cent China Normal Univ, Sch Life Sci, Wuhan, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Qiu, Guo-Wei; Jiang, HB; Jiang, Hai-Bo; Zang, Sha-Sha; Lou, Wen-Jing; Li, Ding-Lan; Li, Zheng-Ke; Sun, Chuan-Yu] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Hubei, Peoples R China.;[Yang, Nina; Fu, Fei-Xue; Hutchins, David A.] Univ Southern Calif, Dept Biol Sci, Marine & Environm Biol, Los Angeles, CA USA.
通讯机构:
[Jiang, HB; Qiu, BS] C;Cent China Normal Univ, Sch Life Sci, Wuhan, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Hubei, Peoples R China.
摘要:
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. 55 Fe 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.
作者机构:
[Qiu, Bao-Sheng; Zhang, Lu-Dan; Li, Zheng-Ke; Dai, Guo-Zheng; Yin, Yan-Chao; Zhang, Zhong-Chun] Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Zhang, Lu-Dan; Li, Zheng-Ke; Dai, Guo-Zheng; Yin, Yan-Chao; Zhang, Zhong-Chun] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.;[Chen, Min] Univ Sydney, Sch Life & Environm Sci, Sydney, NSW 2006, Australia.
通讯机构:
[Qiu, Bao-Sheng] C;[Chen, Min] U;Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.;Univ Sydney, Sch Life & Environm Sci, Sydney, NSW 2006, Australia.
会议名称:
Light Harvesting Satellite Meeting held in conjunction with the 17th International Congress on Photosynthesis Research
会议时间:
AUG, 2016
会议地点:
Egmond aan Zee, NETHERLANDS
会议主办单位:
[Li, Zheng-Ke;Yin, Yan-Chao;Zhang, Lu-Dan;Zhang, Zhong-Chun;Dai, Guo-Zheng;Qiu, Bao-Sheng] Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.^[Li, Zheng-Ke;Yin, Yan-Chao;Zhang, Lu-Dan;Zhang, Zhong-Chun;Dai, Guo-Zheng;Qiu, Bao-Sheng] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.^[Chen, Min] Univ Sydney, Sch Life & Environm Sci, Sydney, NSW 2006, Australia.
关键词:
Accessory chlorophyll-binding proteins (CBPs);Iron limitation;Iron-stress-induced protein A (IsiA);Photosynthesis;Six transmembrane helix family of chlorophyll-binding proteins/antenna;Acaryochloris marina
作者机构:
[Qiu, Bao-Sheng; Liu, Shu-Wen; Li, Zheng-Ke; Xu, Kui] Cent China Normal Univ, Sch Life Sci, Wuhan, Peoples R China.;[Qiu, Bao-Sheng; Liu, Shu-Wen; Li, Zheng-Ke; Xu, Kui] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Peoples R China.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Sch Life Sci, Wuhan, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan, Peoples R China.
摘要:
<jats:title>SUMMARY</jats:title><jats:p>Cyanobacterial blooms are found in many freshwater ecosystems around the world, but the effect of environmental factors on their growth and the proportion of species still require more investigation. In this study, the physiological responses of bloom‐forming cyanobacteria <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>icrocystis aeruginosa</jats:italic> <jats:styled-content style="fixed-case">FACHB</jats:styled-content>912, <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>icrocystis flos‐aquae</jats:italic> <jats:styled-content style="fixed-case">FACHB</jats:styled-content>1028 and <jats:styled-content style="fixed-case">
<jats:italic>P</jats:italic>
</jats:styled-content>
<jats:italic>seudanabaena</jats:italic> sp. <jats:styled-content style="fixed-case">FACHB1</jats:styled-content>282 to iron deficiency were investigated. Their specific growth rates were found to decrease as the available iron concentration decreased. At low available iron concentrations of 1 × 10<jats:sup>−7</jats:sup> M (pFe 21.3) and 5 × 10<jats:sup>−8</jats:sup> M (pFe 21.6), <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. aeruginosa</jats:italic> had the lowest specific growth rate among three studied species. The cell sizes of <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. flos‐aquae</jats:italic> and <jats:italic>Pseudanabaena</jats:italic> sp. were significantly smaller under the lowest iron concentration. The chlorophyll <jats:italic>a</jats:italic> content of the three species decreased at the lowest iron concentration. The maximal relative electron transport rate, photosynthetic efficiency, and light‐saturation parameter of <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. aeruginosa</jats:italic> were lower than the other two cyanobacteria at pFe 21.3. Therefore, <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. aeruginosa</jats:italic> was the least able to adapt to iron deficiency. Under iron deficiency, the functional absorption cross‐section of <jats:styled-content style="fixed-case">PSII</jats:styled-content> and electron transport rate on the acceptor side of <jats:styled-content style="fixed-case">PSII</jats:styled-content> decreased in <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. aeruginosa</jats:italic>, while the connectivity factor between individual photosynthetic units increased in <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. flos‐aquae</jats:italic>, and the electron transport rate on the acceptor side of <jats:styled-content style="fixed-case">PSII</jats:styled-content> and between <jats:styled-content style="fixed-case">PSII</jats:styled-content> and <jats:styled-content style="fixed-case">PSI</jats:styled-content> decreased in <jats:styled-content style="fixed-case">
<jats:italic>P</jats:italic>
</jats:styled-content>
<jats:italic>seudanabaena</jats:italic> sp. The ability to store iron was highest in <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. flos‐aquae</jats:italic>, followed by <jats:styled-content style="fixed-case">
<jats:italic>P</jats:italic>
</jats:styled-content>
<jats:italic>seudanabaena</jats:italic> sp. and <jats:styled-content style="fixed-case">
<jats:italic>M</jats:italic>
</jats:styled-content>
<jats:italic>. aeruginosa</jats:italic>. Thus, these results provide necessary information for detecting the role of iron in the succession of cyanobacterial species in Lake Taihu, the third largest freshwater lake in China, because all three species were isolated from this lake.</jats:p>
作者机构:
[Qiu, Bao-Sheng; Jiang, Hai-Bo; Zang, Sha-Sha; Song, Wei-Yu] Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;[Qiu, Bao-Sheng; Jiang, Hai-Bo; Zang, Sha-Sha; Song, Wei-Yu] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.;[Chen, Min] Univ Sydney, Sch Life & Environm Sci, Sydney, NSW 2006, Australia.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Wuhan 430079, Hubei, Peoples R China.
摘要:
The sulfur-formation (
suf
) genes play important roles in both photosynthesis and respiration of cyanobacteria, but the organism prioritizes Fe–S clusters for respiration at the expense of photosynthesis.
Iron–sulfur (Fe–S) clusters are important to all living organisms, but their assembly mechanism is poorly understood in photosynthetic organisms. Unlike non-photosynthetic bacteria that rely on the iron–sulfur cluster system, Synechocystis sp. PCC 6803 uses the Sulfur-Formation (SUF) system as its major Fe–S cluster assembly pathway. The co-expression of suf genes and the direct interactions among SUF subunits indicate that Fe–S assembly is a complex process in which no suf genes can be knocked out completely. In this study, we developed a condition-controlled SUF Knockdown mutant by inserting the petE promoter, which is regulated by Cu2+ concentration, in front of the suf operon. Limited amount of the SUF system resulted in decreased chlorophyll contents and photosystem activities, and a lower PSI/PSII ratio. Unexpectedly, increased cyclic electron transport and a decreased dark respiration rate were only observed under photoautotrophic growth conditions. No visible effects on the phenotype of SUF Knockdown mutant were observed under heterotrophic culture conditions. The phylogenetic distribution of the SUF system indicates that it has a co-evolutionary relationship with photosynthetic energy storing pathways.
通讯机构:
[Qiu, Bao-Sheng] C;Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Sch Life Sci, Wuhan 430079, Hubei, Peoples R China.
关键词:
iron deficiency;Microcystis;photosynthesis;Synechococcus;UV-B
摘要:
Iron deficiency has been considered one of the main limiting factors of phytoplankton productivity in some aquatic systems including oceans and lakes. Concomitantly, solar ultraviolet-B radiation has been shown to have both deleterious and positive impacts on phytoplankton productivity. However, how iron-deficient cyanobacteria respond to UV-B radiation has been largely overlooked in aquatic systems. In this study, physiological responses of four cyanobacterial strains (Microcystis and Synechococcus), which are widely distributed in freshwater or marine systems, were investigated under different UV-B irradiances and iron conditions. The growth, photosynthetic pigment composition, photosynthetic activity, and nonphotochemical quenching of the different cyanobacterial strains were drastically altered by enhanced UV-B radiation under iron-deficient conditions, but were less affected under iron-replete conditions. Intracellular reactive oxygen species (ROS) and iron content increased and decreased, respectively, with increased UV-B radiation under iron-deficient conditions for both Microcystis aeruginosa FACHB 912 and Synechococcus sp. WH8102. On the contrary, intracellular ROS and iron content of these two strains remained constant and increased, respectively, with increased UV-B radiation under iron-replete conditions. These results indicate that iron-deficient cyanobacteria are more susceptible to enhanced UV-B radiation. Therefore, UV-B radiation probably plays an important role in influencing primary productivity in iron-deficient aquatic systems, suggesting that its effects on the phytoplankton productivity may be underestimated in iron-deficient regions around the world.
作者机构:
[Qiu, Baosheng; Li, Yunxia; Zhang, Zhongchun; Yu, Qi] Cent China Normal Univ, Hubei Key Lab Genet Regulat & Integrat Biol, Sch Life Sci, Wuhan, Hubei, Peoples R China.;[Liu, Pingping; Chen, Qiansi; Zhou, Huina] Zhengzhou Tobacco Res Inst CNTC, Zhengzhou, Henan, Peoples R China.;[Mendoza-Cozatl, David G.] Univ Missouri, Div Plant Sci, CS Bond Life Sci Ctr, Columbia, MO USA.
通讯机构:
[Liu, PP; Chen, QS] Z;Zhengzhou Tobacco Res Inst CNTC, Zhengzhou, Henan, Peoples R China.
摘要:
Due to their extraordinary capacity to hypertolerate and hyperaccumulate heavy metals in above-ground tissues, hyperaccumulator plant species have gained wide attention from researchers seeking biotechnologies to manage environmental heavy metal pollution. However, the molecular basis of hyperaccumulation is still far from being fully understood. Here, we used iTRAQ to perform a quantitative proteomics study of the leaves of Sedum alfredii (Crassulaceae) from hyperaccumulating population (HP) and non-hyperaccumulating population (NHP). A total of 248 proteins had constitutively higher levels in HP leaves than in NHP leaves. Cadmium (Cd) treatment led to the induction of 13 proteins in HP leaves and 33 proteins in NHP leaves. Two proteins were induced by Cd in both HP leaves and NHP leaves. The annotations for many of the proteins that were higher in HP leaves and proteins that were induced by Cd treatments were associated with vacuolar sequestration, cell wall/membrane modification, and plant defense. In addition to establishing a global empirical foundation for the study of proteins in S. alfredii, our findings relating to the differential constitutive and inducible expression of proteins open potential new research avenues and bolster previously reported suppositions about Cd hyperaccumulation in hyperaccumulator plants.