scholarly journals Effects of Modification of Light Parameters on the Production of Cryptophycin, Cyanotoxin with Potent Anticancer Activity, in Nostoc sp.

Toxins ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 809
Author(s):  
Alexandros Polyzois ◽  
Diana Kirilovsky ◽  
Thi-hanh Dufat ◽  
Sylvie Michel
Keyword(s):  
Light Stress ◽  
Red Light ◽  
Major Effect ◽  
High Light Intensity ◽  
Efficient Production ◽  
Lower Growth ◽  
Noticeable Increase ◽  
Lower Growth Rate ◽  
Industrial Use ◽  
Effect Of Light

Cryptophycin-1 is a cyanotoxin produced by filamentous cyanobacteria. It has been evaluated as an anticancer agent with great potential. However, its synthesis provides insufficient yield for industrial use. An alternative solution for metabolite efficient production is to stress cyanobacteria by modifying the environmental conditions of the culture (Nostoc sp. ATCC 53789). Here, we examined the effects of light photoperiod, wavelength, and intensity. In light photoperiod, photoperiods 24:0 and 16:8 (light:dark) were tested while in wavelength, orange-red light was compared with blue. Medium, high, and very high light intensity experiments were performed to test the effect of light stress. For a 10-day period, growth was measured, metabolite concentration was calculated through HPLC, and the related curves were drawn. The differentiation of light wavelength had a major effect on the culture, as orange-red filter contributed to noticeable increase in both growth and doubled the cyanotoxin concentration in comparison to blue light. Remarkably, constant light provides higher cryptophycin yield, but slightly lower growth rate. Lastly, the microorganism prefers medium light intensities for both growth and metabolite expression. The combination of these optimal conditions would contribute to the further exploitation of cryptophycin.

scholarly journals Guard cells control hypocotyl elongation through HXK1, HY5, and PIF4

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Gilor Kelly ◽  
Danja Brandsma ◽  
Aiman Egbaria ◽  
Ofer Stein ◽  
Adi Doron-Faigenboim ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Blue Light ◽  
Opposite Effect ◽  
Red Light ◽  
Guard Cells ◽  
Cell Types ◽  
Hypocotyl Elongation ◽  
Sugar Production ◽  
Effect Of Light

AbstractThe hypocotyls of germinating seedlings elongate in a search for light to enable autotrophic sugar production. Upon exposure to light, photoreceptors that are activated by blue and red light halt elongation by preventing the degradation of the hypocotyl-elongation inhibitor HY5 and by inhibiting the activity of the elongation-promoting transcription factors PIFs. The question of how sugar affects hypocotyl elongation and which cell types stimulate and stop that elongation remains unresolved. We found that overexpression of a sugar sensor, Arabidopsis hexokinase 1 (HXK1), in guard cells promotes hypocotyl elongation under white and blue light through PIF4. Furthermore, expression of PIF4 in guard cells is sufficient to promote hypocotyl elongation in the light, while expression of HY5 in guard cells is sufficient to inhibit the elongation of the hy5 mutant and the elongation stimulated by HXK1. HY5 exits the guard cells and inhibits hypocotyl elongation, but is degraded in the dark. We also show that the inhibition of hypocotyl elongation by guard cells’ HY5 involves auto-activation of HY5 expression in other tissues. It appears that guard cells are capable of coordinating hypocotyl elongation and that sugar and HXK1 have the opposite effect of light on hypocotyl elongation, converging at PIF4.

Monitoring of cold and light stress impact on photosynthesis by using the laser induced fluorescence transient (LIFT) approach

2010 ◽  
Vol 37 (5) ◽  
pp. 395 ◽  
Author(s):  
Roland Pieruschka ◽  
Denis Klimov ◽  
Zbigniew S. Kolber ◽  
Joseph A. Berry
Keyword(s):  
Photosynthetic Efficiency ◽  
Light Stress ◽  
Pulse Amplitude ◽  
Laser Induced Fluorescence ◽  
High Light Intensity ◽  
High Light ◽  
Persea Americana ◽  
Effective Quantum Yield ◽  
Fluorescence Transient ◽  
Fluorescence Measurements

Chlorophyll fluorescence measurements have been widely applied to quantify the photosynthetic efficiency of plants non-destructively. The most commonly used pulse amplitude modulated (PAM) technique provides a saturating light pulse, which is not practical at the canopy scale. We report here on a recently developed technique, laser induced fluorescence transient (LIFT), which is capable of remotely measuring the photosynthetic efficiency of selected leaves at a distance of up to 50 m. The LIFT approach correlated well with gas exchange measurements under laboratory conditions and was tested in a field experiment monitoring the combined effect of low temperatures and high light intensity on a variety of plants during the early winter in California. We observed a reduction in maximum and effective quantum yield in electron transport for Capsicum annuum L., Lycopersicon esculentum L. and Persea americana Mill. as the temperatures fell, while a grass community was not affected by combined low temperature and high light stress. The ability to make continuous, automatic and remote measurements of the photosynthetic efficiency of leaves with the LIFT system provides a new approach for studying and monitoring of stress effects on the canopy scale.

scholarly journals Widespread variation in heat tolerance and symbiont load are associated with growth tradeoffs in the coral Acropora hyacinthus in Palau

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Brendan Cornwell ◽  
Katrina Armstrong ◽  
Nia S Walker ◽  
Marilla Lippert ◽  
Victor Nestor ◽  
...  
Keyword(s):  
Climate Change ◽  
Large Scale ◽  
Habitat Restoration ◽  
Natural Resistance ◽  
Lower Growth ◽  
Coral Reef Resilience ◽  
The Face ◽  
Lower Growth Rate ◽  
Acropora Hyacinthus ◽  
The Cost

Climate change is dramatically changing ecosystem composition and productivity, leading scientists to consider the best approaches to map natural resistance and foster ecosystem resilience in the face of these changes. Here we present results from a large-scale experimental assessment of coral bleaching resistance, a critical trait for coral population persistence as oceans warm, in 221 colonies of the coral Acropora hyacinthus across 37 reefs in Palau. We find that bleaching resistant individuals inhabit most reefs but are found more often in warmer microhabitats. Our survey also found wide variation in symbiont concentration among colonies, and that colonies with lower symbiont load tended to be more bleaching resistant. By contrast, our data show that low symbiont load comes at the cost of lower growth rate, a tradeoff that may operate widely among corals across environments. Corals with high bleaching resistance have been suggested as a source for habitat restoration or selective breeding in order to increase coral reef resilience to climate change. Our maps show where these resilience corals can be found, but the existence of tradeoffs with heat resistance may suggest caution in unilateral use of this one trait in restoration.

Is the in vivo Photosystem I Function Resistant to Photoinhibition? An Answer from Photoacoustic and Far-Red Absorbance Measurements in Intact Leaves

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1038-1044 ◽  
Author(s):  
Michel Havaux ◽  
Murielle Eyletters
Keyword(s):  
Light Stress ◽  
Red Light ◽  
Light Treatment ◽  
High Light ◽  
Saturation Curve ◽  
Strong Light ◽  
Ps Ii ◽  
Fluorescence Measurements ◽  
Ps I

Abstract Preillumination of intact pea leaves with a strong blue-green light of 400 W m-2 markedly inhibited both photoacoustically monitored O2-evolution activity and PS II photochemistry as estimated from chlorophyll fluorescence measurements. The aim of the present work was to examine, with the help of the photoacoustic technique, whether this high-light treatment deteriorated the in vivo PS I function too. High-frequency photoacoustic measurements indicated that photochemical conversion of far-red light energy in PS I was preserved (and even transiently stimulated) whereas photochemical energy storage monitored in light exciting both PS I and PS II was markedly diminished. Low-frequency photoacoustic measurements of the Emerson enhancement showed a spectacular change in the PS II/PS I activity balance in favor of PS I. It was also observed that the linear portion of the saturation curve of the far-red light effect in the Emerson enhancement was not changed by the light treatment. Those results lead to the conclusion that, in contrast to PS II, the in vivo PS I photofunctioning was resistant to strong light stress, thus confirming previous suggestions derived from in vitro studies. Estimation of the redox state of the PS I reaction center by leaf absorbance measurements at ca. 820 nm suggested that, under steady illumination, a considerably larger fraction of PS I centers were in the closed state in high-light pretreated leaves as compared to control leaves, presumably allowing passive adjustment of the macroscopic quantum yield of PS I photochemis­ try to the strongly reduced photochemical efficiency of photoinhibited PS II.

Does Astaxanthin Protect Haematococcus against Light Damage?

1998 ◽  
Vol 53 (1-2) ◽  
pp. 93-100 ◽  
Author(s):  
Lu Fan ◽  
Avigad Vonshak ◽  
Aliza Zarka ◽  
Sammy Boussiba
Keyword(s):  
Light Intensity ◽  
Light Stress ◽  
Phosphate Starvation ◽  
High Light Intensity ◽  
High Irradiance ◽  
High Light ◽  
Protective Agent ◽  
Light Damage ◽  
Low Light ◽  
Very High

Abstract The photoprotective function of the ketocarotenoid astaxanthin in Haematococcus was questioned. When exposed to high irradiance and/or nutritional stress, green Haematococcus cells turned red due to accumulation of an immense quantity of the red pigment astaxanthin. Our results demonstrate that: 1) The addition of diphenylamine, an inhibitor of astaxanthin biosynthesis, causes cell death under high light intensity; 2) Red cells are susceptible to high light stress to the same extent or even higher then green ones upon exposure to a very high light intensity (4000 μmol photon m-2 s-1); 3) Addition of 1O2 generators (methylene blue, rose bengal) under noninductive conditions (low light of 100 (μmol photon m-2 s-1) induced astaxanthin accumulation. This can be reversed by an exogenous 1O2 quencher (histidine); 4) Histidine can prevent the accumulation of astaxanthin induced by phosphate starvation. We suggest that: 1) Astaxanthin is the result of the photoprotection process rather than the protective agent; 2) 1O2 is involved indirectly in astaxanthin accumulation process.

Settlement and Metamorphosis in Barnacles and Decapods

2020 ◽  
pp. 223-254
Author(s):  
Paulina Gebauer ◽  
Luis Giménez ◽  
Iván Hinojosa ◽  
Kurt Paschke
Keyword(s):  
Adult Population ◽  
Subsequent Development ◽  
Suitable Habitat ◽  
Pelagic Larva ◽  
Lower Growth ◽  
Settlement Behavior ◽  
Biphasic Life Cycle ◽  
Settlement And Metamorphosis ◽  
Lower Growth Rate ◽  
Adult Habitat

Settlement and metamorphosis are two crucial processes in organisms with a biphasic life cycle, forming the link between the pelagic larva and benthic juvenile-adult. In general, these processes occur during the final larval stage. Among crustaceans, settlement behavior and the cues that trigger settlement and metamorphosis have been studied in greater depth in barnacles than in decapods, likely a result of the former losing the ability to move after they join the benthic juvenile-adult population, undergoing metamorphosis. Both barnacles and decapods respond to different environmental cues associated with the adult habitat, such as substratum, biofilm, and the presence of conspecifics. In the absence of cues, larvae can delay their metamorphosis for a period of time. This ability to prolong the development can be advantageous because it increases the probability of settling in a suitable habitat. However, delayed metamorphosis has also associated costs (e.g., smaller size, lower growth rate, and higher mortality), which may be carried over to subsequent development stages, with consequences for recruitment.

scholarly journals Stereoisomers of Colourless Carotenoids from the Marine Microalga Dunaliella salina

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1880 ◽  
Author(s):  
Laura Mazzucchi ◽  
Yanan Xu ◽  
Patricia Harvey
Keyword(s):  
Dunaliella Salina ◽  
Light Stress ◽  
Red Light ◽  
Chemical Properties ◽  
Phytoene Desaturase ◽  
Cell Factory ◽  
Geranylgeranyl Diphosphate ◽  
Diverse Range ◽  
Marine Microalga ◽  
Β Carotene

Carotenoids comprise a diverse range of naturally occurring stereoisomers, which differ in their physico-chemical properties. Their biosynthesis begins with phytoene, which is a rarity among carotenoids because it is colourless. Phytoene is sought after as a skin protectant against harmful UV range B (290–320 nm) and C (100–290 nm) light, and as a natural skin-whitening agent and is synthesized from geranylgeranyl diphosphate. Geranylgeranyl diphosphate is catalysed by phytoene synthase and phytoene desaturase to phytoene and phytofluene, respectively. The subsequent steps involve desaturation, isomerisation and cyclisation reactions to form α- and β-carotene stereoisomers, via all-trans lycopene. The marine microalga Dunaliella salina is the richest source of β-carotene, but it can accumulate phytoene and phytofluene as well. In the present study, different analytical tools including High-Performance Liquid Chromatography (HPLC), Ultra-Performance Convergence Chromatography (UPC2-MS) and Nuclear Magnetic Resonance (NMR) were used to characterize and quantify the phytoene isomeric configurations in D. salina in order to explore both the feasibility of D. salina as a cell factory for phytoene production and to gain new insight into the carotenoid synthesis pathway in D. salina. D. salina, similar to tomato, produced predominantly 15-cis phytoene isomer (>98%) and a trace amount of all-trans phytoene (<2%). High light stress, red light stress, or use of a phytoene desaturase inhibitor or a mitotic disrupter herbicide led to the accumulation of 15-cis phytoene but not all-trans phytoene. 9-cis phytoene was not detected in any of the extracts of D. salina biomass. Our main findings suggest that 15-cis phytoene is the most abundant isomer in D. salina and that it is subject to a series of isomerisation and desaturation reactions to form all-trans and 9-cis β-carotene.

Caecotrophes intake in growing rabbits estimated either from urinary excretion of purine derivatives or from direct measurement using animals provided with a neck collar: effect of type and level of dietary carbohydrate

2002 ◽  
Vol 74 (1) ◽  
pp. 135-144 ◽  
Author(s):  
A. Belenguer ◽  
J. Balcells ◽  
M. Fondevila ◽  
C. Torre
Keyword(s):  
Growth Rate ◽  
Dry Matter ◽  
Dry Matter Intake ◽  
Purine Derivatives ◽  
Lower Growth ◽  
Beet Pulp ◽  
Lower Growth Rate ◽  
Maize Grain ◽  
G Ratio ◽  
Microbial N

AbstractThe present study compares estimates of caecotrophes production from urinary purine derivatives (PD) excretion with that from preventing caecotrophy by using a neck collar. A total of 64 New Zealand growing male rabbits were used to study the effect of diet composition on caecotrophes production. Diets were formulated using two sources of structural carbohydrates (fibre): alfalfa hay (AH) and sugar-beet pulp (SBP), mixed at two constant proportions, (0·75: 0·25) AH diets and (0·25: 0·75) SBP diets. Both diets included either barley or maize grain at two fibre: grain ratios (F/G, 80: 20 and 45: 55). Diets were given ad libitum. Growth rate, dry matter intake and digestibility were not modified by the grain source, although high F/G diets resulted in a lower growth rate (19·8 v. 26·4 g/day; P < 0·001). Between fibre sources, dry-matter intake and growth were higher in AH than in SBP diets (122·5 and 25·6 v. 101·6 and 20·4 g/day, respectively, P < 0·001 and P < 0·01). Rabbits given high F/G ratio and AH diets excreted more caecotrophes than those given low F/G ratio and SBP diets (19·5 and 20·9 v. 16·3 and 14·85 g/day, respectively). Microbial-N recycling through the caecotrophy process was higher when considering data from PD excretion (1·33 g/d) than when estimated by preventing caecotrophy (0·72 g/day).

scholarly journals Physiological response of Monimopetalum chinense to light stress under habitat fragmentation

2010 ◽  
Vol 56 (No. 12) ◽  
pp. 551-556 ◽  
Author(s):  
C. Hao ◽  
R. Fan ◽  
X. Zhang ◽  
L. Wang ◽  
W. Chen ◽  
...  
Keyword(s):  
Antioxidant Enzymes ◽  
Habitat Fragmentation ◽  
Light Intensity ◽  
Physiological Responses ◽  
Light Stress ◽  
Strong Light ◽  
Malondialdehyde Content ◽  
Antioxidant Enzymes Activities ◽  
Intense Light ◽  
Effect Of Light

To determine the effect of light stress under fragmental habitat on the physiology, this paper investigated the physiological responses of Monimopetalum chinense with different light intensities in the Xianyu Mountains (Anhui, China). The study showed that both weak and intense light brought about by habitat fragmentation could improve antioxidant enzymes activities, and promote electrical conductivity and malondialdehyde content of M. chinense leaves. However, too strong light could inhibit photosynthesis rates, superoxide dismutase, catalase, and ascorbate peroxidase activities. In addition, the characteristics of leaves were affected by light intensity at the fragmental habitat. Specifically, intense light was disadvantageous to photosynthesis and antioxidant enzymes of the species. Our results suggest that the biodiversity conservation of M. chinense is necessary, and that light intensity should be considered carefully when implementing conservation efforts. &nbsp;

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