RETRACTED ARTICLE: Increased biomass productivity in green algae by tuning non-photochemical quenching

Berteotti, Silvia; Ballottari, Matteo; Bassi, Roberto

doi:10.1038/srep21339

Cited by 67 publications

(47 citation statements)

References 43 publications

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“…A similar behavior was also observed in high light, with the maximum NPQ level observed in transformed lines only at the beginning of the measurement. Maximum NPQ level observed in the transformed line was thus much lower compared to WT (Figure 3D); the dependency of NPQ maximum induction vs. accumulation of LHCSR3 protein is reported in Supplemental data Figure S3, suggesting a linear correlation between the amount of LHCSR3 per chlorophyll and the maximum NPQ value observed, which is in agreement with previous reports [20,38]. Moreover, NPQ in complemented lines decreases after few minutes in low light or seconds in high light; this result can be related to light-dependent activation of the Calvin cycle and de-saturation of photosynthetic electron chain.…”

Section: Resultssupporting

confidence: 92%

“…Growth analysis in liquid medium was performed in a small scale photobioreactors provided by Multi-Cultivator MC 1000 (Photon System Instruments, Brno, Czech Republic) as described in [20]. The samples were grown for one day at 70 μmol m −2 ·s −1 , and then at 400 μmol m −2 ·s −1 .…”

Section: Methodsmentioning

confidence: 99%

“…Immunoblot assays with antibodies against different polypeptides were performed as previously described [20,42]. …”

Section: Methodsmentioning

confidence: 99%

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LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae

Perozeni

Stella

Ballottari

2018

IJMS

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Microalgae are unicellular photosynthetic organisms considered as potential alternative sources for biomass, biofuels or high value products. However, limited biomass productivity is commonly experienced in their cultivating system despite their high potential. One of the reasons for this limitation is the high thermal dissipation of the light absorbed by the outer layers of the cultures exposed to high light caused by the activation of a photoprotective mechanism called non-photochemical quenching (NPQ). In the model organism for green algae Chlamydomonas reinhardtii, NPQ is triggered by pigment binding proteins called light-harvesting-complexes-stress-related (LHCSRs), which are over-accumulated in high light. It was recently reported that biomass productivity can be increased both in microalgae and higher plants by properly tuning NPQ induction. In this work increased light use efficiency is reported by introducing in C. reinhardtii a LHCSR3 gene under the control of Heat Shock Protein 70/RUBISCO small chain 2 promoter in a npq4 lhcsr1 background, a mutant strain knockout for all LHCSR genes. This complementation strategy leads to a low expression of LHCSR3, causing a strong reduction of NPQ induction but is still capable of protecting from photodamage at high irradiance, resulting in an improved photosynthetic efficiency and higher biomass accumulation.

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Section: Resultssupporting

confidence: 92%

Section: Methodsmentioning

confidence: 99%

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LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae

Perozeni

Stella

Ballottari

2018

IJMS

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“…The presence of LHCSR1 can explain the large NPQ observed recently in the npq4 mutant of C. reinhardtii, which lacks LHCSR3 but still contains LHCSR1 (41).…”

Section: Discussionmentioning

confidence: 81%

LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells

Dinc¹,

Tian²,

Roy³

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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To avoid photodamage, photosynthetic organisms are able to thermally dissipate the energy absorbed in excess in a process known as nonphotochemical quenching (NPQ). Although NPQ has been studied extensively, the major players and the mechanism of quenching remain debated. This is a result of the difficulty in extracting molecular information from in vivo experiments and the absence of a validation system for in vitro experiments. Here, we have created a minimal cell of the green alga Chlamydomonas reinhardtii that is able to undergo NPQ. We show that LHCII, the main light harvesting complex of algae, cannot switch to a quenched conformation in response to pH changes by itself. Instead, a small amount of the protein LHCSR1 (light-harvesting complex stress related 1) is able to induce a large, fast, and reversible pH-dependent quenching in an LHCII-containing membrane. These results strongly suggest that LHCSR1 acts as pH sensor and that it modulates the excited state lifetimes of a large array of LHCII, also explaining the NPQ observed in the LHCSR3-less mutant. The possible quenching mechanisms are discussed.photosynthesis | light-harvesting | nonphotochemical quenching | green algae | thylakoid membranes P hotosynthetic organisms get their energy from light and have developed a series of mechanisms to respond to the changes in light intensity that occur in their natural environment (1, 2). This is particularly important in high-light conditions, as the energy absorbed in excess can induce photodamage, eventually leading to the death of the organism. Photosynthetic organisms are equipped with many pigment-protein complexes, most of which in plants and green algae are members of the light-harvesting complex (Lhc) multigenic family (3). These complexes maximize light absorption in low light, but can easily become overexcited in high light (4), when a large part of the absorbed light cannot be used for charge separation in the reaction centers of the photosystems. Especially when the changes in light intensity are very fast, and thus protein degradation is not an option, photoprotective mechanisms need to be switched on to avoid the formation of singlet oxygen. The most rapid response to high light intensity is the dissipation of a large part of the absorbed energy as heat in a series of processes known as nonphotochemical quenching (NPQ) (1,5,6).The general idea is that the LHCs can switch between a lightharvesting conformation, characterized by a long excited-state lifetime, and a quenched (Q) conformation that shows a shorter lifetime because of the presence of competing de-excitation processes (7). How this switch is induced and the nature of these de-excitation processes is a matter of debate. It is known that NPQ is triggered by low luminal pH, which is a signal for the overexcitation of the membrane; this activates the quenching processes (5, 8), which involves the proteins PsbS (in plants and mosses) (9, 10) and/or lightharvesting complex stress related (LHCSR) (in green algae, mosses, and diatoms) (10-12)....

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“…Growth in liquid medium was performed using a MultiCultivator OD-1000 system from Photon Systems Instruments () as described in [75]. The instrument is composed of 8 tubes immersed in a thermostatic bath.…”

Section: Methodsmentioning

confidence: 99%

Microalgae Cultivation on Anaerobic Digestate of Municipal Wastewater, Sewage Sludge and Agro-Waste

Zuliani

Frison

Jelić

et al. 2016

IJMS

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Microalgae are fast-growing photosynthetic organisms which have the potential to be exploited as an alternative source of liquid fuels to meet growing global energy demand. The cultivation of microalgae, however, still needs to be improved in order to reduce the cost of the biomass produced. Among the major costs encountered for algal cultivation are the costs for nutrients such as CO2, nitrogen and phosphorous. In this work, therefore, different microalgal strains were cultivated using as nutrient sources three different anaerobic digestates deriving from municipal wastewater, sewage sludge or agro-waste treatment plants. In particular, anaerobic digestates deriving from agro-waste or sewage sludge treatment induced a more than 300% increase in lipid production per volume in Chlorella vulgaris cultures grown in a closed photobioreactor, and a strong increase in carotenoid accumulation in different microalgae species. Conversely, a digestate originating from a pilot scale anaerobic upflow sludge blanket (UASB) was used to increase biomass production when added to an artificial nutrient-supplemented medium. The results herein demonstrate the possibility of improving biomass accumulation or lipid production using different anaerobic digestates.

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RETRACTED ARTICLE: Increased biomass productivity in green algae by tuning non-photochemical quenching

Cited by 67 publications

References 43 publications

LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae

LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae

LHCSR1 induces a fast and reversible pH-dependent fluorescence quenching in LHCII in Chlamydomonas reinhardtii cells

Microalgae Cultivation on Anaerobic Digestate of Municipal Wastewater, Sewage Sludge and Agro-Waste

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