High Light Intensity Conditions Research Articles

High Productivity of Eicosapentaenoic Acid and Fucoxanthin by a Marine Diatom Chaetoceros gracilis in a Semi-Continuous Culture.

Significantly high eicosapentaenoic acid (EPA) and fucoxanthin contents with high production rate were achieved in semi continuous culture of marine diatom. Effects of dilution rate on the production of biomass and high value biocompounds such as EPA and fucoxanthin were evaluated in semi-continuous cultures of Chaetoceros gracilis under high light condition. Cellular dry weight increased at lower dilution rate and higher light intensity conditions, and cell size strongly affected EPA and fucoxanthin contents. The smaller microalgae cells showed significantly higher (p < 0.05) value of 17.1 mg g-dw–1 fucoxanthin and 41.5% EPA content per total fatty acid compared to those observed in the larger cells. Chaetoceros gracilis can accumulate relatively higher EPA and fucoxanthin than those reported previously. In addition, maintenance of small cell size by supplying sufficient nutrients and light energy can be the key for the increase production of valuable biocompounds in C. gracilis.

Analysis of β-d-glucan biosynthetic genes in oat reveals glucan synthesis regulation by light.

Oat (Avena sativa) has human health benefits when consumed as a whole-grain food, attributed to the high content of (1,3;1,4)-β-d-glucan (mixed-linkage glucan [MLG]), but little is known about the synthase genes and synthesis mechanism of MLG polysaccharides in this species. The concentration of oat MLGs under different light intensities was measured by a standard enzymatic approach and further verified by immunoelectron microscopy. The effect of light intensity on MLG synthase genes was examined by RT-qPCR and western blot analyses. The pattern of expression directed by the promoter of the oat MLG synthase gene was also investigated by histochemical β-glucuronidase (GUS) analysis. The oat orthologues of genes implicated in the synthesis of MLG in other cereals, including cellulose synthase-like (Csl) F, H and J gene families, were defined. Transcript profiling of these genes across oat tissues indicated that AsCslF6 transcripts dominated. Under high light intensities, the expression of AsCslF6, a major isoform of the MLG synthase genes, increased to >30 % of the dark growth control. The amount of MLG in oat rose from 0.07 to 1.06 % with increased light intensity. Histochemical tests showed that the AsCslF6 gene promoter preferentially directs GUS expression under high light intensity conditions. Oat MLG synthesis is regulated by light. High light intensity upregulates the expression of the MLG synthase AsCslF6 gene, leading to an increase in the amount of MLG in oat leaves.

Characterization of Chlorella sorokiniana and Chlorella vulgaris fatty acid components under a wide range of light intensity and growth temperature for their use as biological resources

This study aims to characterize the potential of three strains of microalgal species (Chlorella sorokiniana KNUA114 and KNUA122; C. vulgaris KNUA104) for use as feedstock, based on their fatty acid compositions. Each strain was molecularly identified using four marker genes (ITS, SSU, rbcL, and tufA) and phylogenetically characterized. C. sorokiniana and C. vulgaris collected from Ulleung Island, South Korea, were homologous with other known species groups. Samples' fatty acid components were measured using GC/MS analysis in growth temperatures of 10 °C, 25 °C, and 35 °C. The growth rate of C. sorokiniana strains was higher than that of C. vulgaris under high-temperature conditions, confirming the potential industrial applicability of the former as feedstock material. Additionally, saturated fatty acid contents and productivities increased as biological resources of the C. sorokiniana strains were higher than those of C. vulgaris under high light intensity and temperature conditions. These results suggest that the fatty acid components of C. sorokiniana strains may potentially be used as biological resources (e.g., feedstock).

Radiation-Activated Pre-Differentiated Retinal Tissue Monitored by Acoustic Wave Biosensor.

A thickness-shear mode acoustic wave biosensor operated within a flow-through system was used to examine the response of mouse retinal tissue to radiation. Control experiments conducted with respect to exposure of the bare gold electrodes of the device under various conditions of light intensity and bathing solution yielded reversible changes in resonant frequency (Fs) and motional resistance (Rm). The magnitude of transient changes was proportional to light intensity, but independent of solution type. These alterations in acoustic parameters were ascribed to acoustic coupling phenomena at the electrode-to-liquid interface. Pre-differentiated retina from mouse samples deposited on the thickness shear mode (TSM) electrode exposed to a high light intensity condition also exhibited reversible changes in both Fs and Rm, compared to control experiments involving a coating used to attach the tissue to the electrode. In this case, the radiation-instigated reversible responses for both acoustic parameters exhibited a reduction in magnitude. The changes are ascribed to the alteration in viscoelasticity of the retinal matrix on the TSM electrode surface. The precise biophysical mechanism responsible for the changes in Fs and Rm remains a challenge, given the complex make up of retinal tissue.

Transcriptome analysis of phototransduction-related genes in tentacles of the sea cucumber Apostichopus japonicus

The sea cucumber Apostichopus japonicus (Selenka)is a typical nocturnal echinoderm, which is believed to be almost completely dependent on light intensity for the regulation of endogenous rhythms. Under conditions of high light intensity, this species shows clear evidence of light avoidance behavior, seeking out shaded areas of reef in which to reside. In this study, we performed RNA-Seq analysis to examine the tentacle transcriptome of A. japonicus specimens that had been subjected to dark and light (5 min and 1 h) conditions. We specifically focused on detecting genes involved in opsin-based light perception, including opsins and members of phototransduction-related pathways. On the basis of comparisons with both vertebrate and invertebrate phototransduction pathways, we determined that components of two of the main metazoan phototransduction pathways were altered in response to illumination. Among the key phototransduction-related genes in tentacles, we identified retinol dehydrogenase, members of the dehydrogenase/reductase family, and myosin III, and also detected a pair of visual pigment-like receptors, peropsin and peropsin-like, the homologous genes of which are believed to have the same function but show opposite expression patterns in response to different light environments. In general, the up-regulation of key genes in sea cucumber exposed to illumination indicated that the tentacles can respond to differences in the light environment at the molecular level.

Characterization of Chlamydomonas Very High Light-tolerant Mutants for Enhanced Lipid Production.

Biodiesel production from microalgae is still not commercially realized due to the high cost of production. High light-tolerance has been suggested as a desirable phenotype for efficient cultivation in large scale production systems under fluctuating outdoor conditions. Nevertheless, it has not been shown if algae with such a phenotype would have better efficiency for lipid production. To determine lipid productivity in high light-tolerant mutants, and to understand the pathways involved in high light-tolerant phenotype, two very high light-tolerant mutants of the green alga Chlamydomonas reinhardtii - CAL028_01_28 and CAL034_01_48 - were selected from eighteen high light-tolerant mutants from the CAL collection. Under high light intensity conditions, and the presence of reactive oxygen species, which are conditions constantly experienced by algae growing in open-pond environments, these strains exhibited higher photosynthetic efficiency and improved survival. The physiological characterization of these mutants revealed that the detoxification of ROS by carotenoids and antioxidant enzymes is crucial for their growth under high light conditions. Neither mutant was affected in terms of its ability to accumulate lipid under nitrogen-depleted condition. More importantly, lipid productivity under high light conditions increased twofold in these mutants compared to that of the wild-type. Taken together, very high light-tolerant mutants confer a high potential for biofuel production under outdoor conditions, and their improved ability to survive under oxidative stress is an important key for efficient growth under outdoor conditions.

Analytical Modeling of Exposure Process in Pinned Photodiode CMOS Image Sensors

The output features of pixels in CMOS image sensors (CISs) are influenced by different exposure conditions. This article presents an analytical model to describe the output characteristics of the exposure process in pinned photodiode (PPD) CMOS image sensors with the accumulation of three charge sources: photogenerated charge, p-n junction-generated charge, and emission charge. In the proposed model, the difference between the time-based and light intensity-based photo response process is illustrated. The model also reveals the relationship between photodiode potential and light intensity at different exposure values. At the low exposure values, the PD potential increases with light intensity, and a contrary trend is observed at the high exposure values. This concludes that a larger linear output range can be obtained in high light intensity conditions. Furthermore, the improved model provides development analysis in terms of light intensity influence for long exposure time noise. The models were verified with technology computer-aided design simulation and the test devices were fabricated using a 0.18- ${\mu }\text{m}$ CIS process. The model demonstrates good consistency with simulation and measured results.

Effect of environmental factors on the biomass and lipid production of microalgae grown in wastewaters

The cultivation of a microalgae-bacteria consortium in a ternary blend of wastewaters was carried out by varying three variables (organic carbon content in the form of glycerol, CO2 addition, and light intensity) using a 23 full factorial design. An analysis of variance was performed to assess the effects of each factor and their interactions on the responses of biomass productivity, lipid content, and nutrients uptake. Also, a principal component analysis (PCA) was conducted to study correlations among the variables. Light intensity and its interaction with organic carbon were the main factors affecting cells growth. The biomass productivity (maximum value of 105.2 mg⋅L−1⋅d−1) was negatively affected by organic carbon and CO2 addition and positively affected by light intensity. Higher lipid contents (maximum value of 17.2%) were found at conditions of low light intensity and high organic carbon in the cultures. Lipid production was related to ammonia-N uptake by the cells. The addition of organic carbon aided the uptake of nitrates-N, ammonia-N, and total organic carbon, and the light intensity reduced these values (maximum values of 100%, 90% and 86%, respectively). The PCA corroborated the relations found between the factors and responses in the factorial analysis and revealed correlations among the responses measured. The main source of nitrogen at conditions of high light intensities was nitrates, while ammonia was the preferred nitrogen source when the cultures were grown under high organic carbon contents as it was indicated by the values of nutrients uptake.

The tomato WV gene encoding a thioredoxin protein is essential for chloroplast development at low temperature and high light intensity

BackgroundChloroplast biogenesis, a complex process in higher plants, is the key to photoautotrophic growth in plants. White virescent (wv) mutants have been used to unfold the molecular mechanisms underlying the regulation of chloroplast development and chloroplast gene expression in plants. However, most of genes controlling white virescent phenotype still remain unknown.ResultsIn this study, we identified a temperature- and light intensity-sensitive mutant, named as wv. The content of chlorophyll was dramatically decreased in the immature leaves of wv mutant under the conditions of low temperature and high-light intensity. TEM observation showed that the chloroplasts in the young leaves of wv mutant lacked an organized thylakoid membrane, whereas crescent-shaped chloroplasts with well-developed stromal and stacked grana thylakoids in the mature leaves were developed. Immunoblot analyses suggested that proteins of photosynthetic complexes were decreased substantially in wv mutants. Based on map-based cloning and transgenic analysis, we determined that the wv phenotype was caused by single base mutation in the first intron of WV gene, which encoded a thioredoxin protein with 365 amino acids. qRT-PCR analysis revealed that the expression of WV gene was significantly down-regulated in wv mutant. In addition, knockdown of WV gene through RNAi also resulted in white virescent young leaves, suggesting that the mutation possibly blocks the differentiation of chloroplasts through inhibiting the expression of WV gene. Furthermore, the expression of WV peaked in apical buds and gradually decreased along with the developmental stage, which was consistent with the wv mutant phenotype. Expression analysis of chloroplast-encoded genes by qRT-PCR showed that the wv mutation affected the expression pattern of chloroplast-encoded PEP dependent genes.ConclusionOur results suggested that wv mutant was sensitive to low temperature and light intensity. WV gene was essential for chloroplast differentiation. A single base mutation in the first intron resulted in down-regulation of WV gene expression, which inhibited the expression of chloroplast-encoded genes, thereby blocking chloroplast formation and chlorophyll synthesis.

Enhancing growth and lipid productivity in Dunaliella salina under high light intensity and nitrogen limited conditions

Microalgae are potential feedstocks for renewable energy production and solving some environmental problems. The effects of nitrogen, sulfur and phosphorus limitations, light intensity (100 or 800 μmol·m−2·s−1) and CO2 concentration (1% or 10%) on growth and lipid accumulation were investigated for Dunaliella salina. The effects of nutrient limitation and light intensity were also characterized by flow cytometry and photosynthetic activity. High light intensity promoted the carbohydrate accumulation and low light intensity was beneficial to lipid accumulation under N-limited conditions. The highest biomass productivity was 1.03 g L−1 d−1 at day 2 under 1% CO2, high light intensity and 1/4 N conditions. The highest lipid productivity was 0.24 g L−1 d−1 at day 2 under 10% CO2, high light intensity and N-limited conditions. A novel approach was proposed and it is helpful for the microalgae biofuel development in future.

Enhanced phycocyanin and protein content of Arthrospira by applying neutral density and red light shading filters: a small‐scale pilot experiment

AbstractBACKGROUNDThe cyanobacterium Arthrospira contains proteins and the blue pigment phycocyanin that can be used as a natural colourant in the food industry. The aim of this study was to investigate a strategy for increasing the yield of phycocyanin and protein from Arthrospira cultures by shading the cultures with neutral density and red light filters. Experiments were conducted under three different irradiance conditions: (i) laboratory tests under relatively low light intensities (100 μmol m−2 s−1), (ii) laboratory tests under relatively high light intensities (516 μmol m−2 s−1) and (iii) scaled‐up tests under natural conditions by cultivating Arthrospira in raceway ponds in a greenhouse.RESULTSIn all cases, shading of cultures with red filters resulted in biomass with increased phycocyanin content achieving a maximum of 134, 71 and 121 mg g−1 under low light intensity, high light intensity and natural conditions, respectively. Under high light intensity and natural conditions, shaded cultures displayed phycocyanin of higher purity and increased protein content, which reached up to 43 and 65%, respectively.CONCLUSIONSShading of Arthrospira cultures by low‐cost polyester red light filters may be an effective way for enhancing phycocyanin production and improving its purity in outdoor ‘spirulina farms’. © 2019 Society of Chemical Industry

Serotonin 5-HT1A Receptor Biased Agonists Display Differential Anxiolytic Activity in a Rat Social Interaction Model.

When placed in an unfamiliar and brightly lit open-field, two adult male rats that have not previously interacted display a low level of social interaction (SI) attributed to an anxiety-like state. The SI test has therefore been used to explore anxiolytic/antistress activity. Here, we investigated the effects of serotonin 5-HT1A receptor agonists displaying various activity profiles, i.e. partial vs full agonist efficacy and pre- versus postsynaptic 5-HT1A receptor preferential activation by "biased agonists". Adult male Sprague-Dawley rats were housed singly before starting the social interaction session. At 30 min before being placed in an open-field, both rats of the dyad were injected (i.p or s.c.) with either vehicle, diazepam (as a reference compound), or one of six 5-HT1A receptor agonists: NLX-101 (a.k.a. F15599), F13714, S15535, flesinoxan, 8-OH-DPAT, and buspirone. Time spent in SI (following, sniffing, playing) was recorded for 10 min. Time spent in SI was inversely correlated with light intensity, with values dropping nearly by half (212.6 ± 18.8 vs 113.7 ± 7.0 s) between 10 and 300 lx (measured at floor level). Under the high light intensity conditions (300 lx), diazepam showed a bell-shaped curve, significantly increasing SI (78% increase in interaction time above control) at 1 mg/kg i.p. only. In the case of 5-HT1A receptor ligands, full agonists, whether nonpreferential (flesinoxan, (±)8-OH-DPAT) or preferential for presynaptic receptors (F13714), showed the strongest activity in this model. The preferential presynaptic receptor partial agonist, S15535, was also active over a wide dose-range, although with lower efficacy than F13714. In contrast, NLX-101, a high-efficacy biased agonist that preferentially activates postsynaptic 5-HT1A receptors, exhibited little activity. The clinical anxiolytic, buspirone, showed a marked effect likely due to its partial agonist activity at 5-HT1A presynaptic receptors. These data support the hypothesis that enhancement of SI in this model is mediated by preferential agonist activation of presynaptic 5-HT1A receptors, and confirm previous studies using local microinjections of (±)8-OH-DPAT. They further support the utility of noninvasive administration of biased agonists for exploring the activity of 5-HT1A receptor subpopulations.

Synergistic effects of abiotic stresses in plants: a case study of nitrogen limitation and saturating light intensity in Arabidopsis thaliana.

Under natural conditions, plants are regularly exposed to combinations of stress factors. A common example is the conjunction between nitrogen (N) deficiency and excess light. The combined effect of stress factors is often ignored in studies using controlled conditions, possibly resulting in misleading conclusions. To address this issue, the present study examined the physiological behavior of Arabidopsis thaliana under the effect of varying nitrogen levels and light intensities. The joint influence of low N and excess light had an adverse effect on plant growth, chlorophyll and anthocyanin concentrations, photochemical capacity and the abundance of proteins involved in carbon assimilation and antioxidative metabolism. In contrast, no adverse physiological responses were observed for plants under either nitrogen limitation or high light (HL) intensity conditions (i.e. single stress). The underlying mechanisms for the increased growth in conditions of HL and sufficient nitrogen were a combination of chlorophyll accumulation and an increased number of proteins involved in C3 carbon assimilation, amino acids biosynthesis and chloroplast development. In contrast, combined stress conditions shifts plants from growth to survival by displaying anthocyanin accumulation and an increased number of proteins involved in catabolism of lipids and amino acids as energy substrates. Ultimately switching plants development from growth to survival. Our results suggest that an assessment of the physiological response to the combined effect of multiple stresses cannot be directly extrapolated from the physiological response to a single stress. Specifically, the synergistic interaction between N deficiency and saturating light in Arabidopsis plants could not have been modeled via only one of the stress factors.

Effect of light intensity and nutrients supply on microalgae cultivated in urban wastewater: Biomass production, lipids accumulation and settleability characteristics

Microalgae cultivation systems fed with wastewater as source of nutrients represents the principal sustainable condition to produce microalgal biomass to be converted conveniently to biofuels. In order to optimize microalgae growth and their lipid content, the effect of light intensity and nutrients load in real wastewater was investigated through batch microalgal cultivation tests. A microalgal polyculture was used as inoculum and grown for 10 days in batch at different conditions of light intensity (i.e. 20, 50 and 100 μmol s−1m−2) and nutrients concentration in wastewater. Experimental results showed that biomass productivity decreased for rich nutrients conditions and increased for high light intensities. The highest lipid mass content (29%) was found for high light intensity condition (100 μmol s−1m−2). Furthermore, microalgae settleability tests, conducted at the end of the cultivation time, resulted in the highest biomass recovery efficiency (72%) for low light intensity and nutrients supply conditions.

Evaluation of climate change impacts and effectiveness of adaptation options on crop yield in the Southeastern United States

The Environmental Policy Integrated Climate (EPIC) model was used to assess the impacts of climate change and proposed adaptation measures on yields of corn (Zea mays L.) and soybean (Glycine max L.) as well as aggregated yields of C3 [soybean, alfalfa (Medicago sativa L.), winter wheat (Triticum aestivum L.)] and C4 [corn, sorghum (Sorghum bicolor L.), pearl millet (Pennisetum glaucum L.)] crop types from representative farms in ten Southeastern US states. Adaptations included annual biochar applications and irrigation. Historical baseline (1979–2009) and future (2041–2070) climate scenarios were used for simulations with baseline and future CO2 concentrations of 360ppmv and 500ppmv, respectively. Four regional climate models (RCMs) nested within global climate models (GCMs) were used to run future simulations. The experiment was analyzed as randomized complete block design with split-plots in time for baseline vs. future comparisons, and as a randomized complete block design with repeated measures for comparisons between future periods within each RCM_GCM model. Compared to historical baseline scenario, increases in future corn yield ranged between 36–83%, but yields decreased by 5–13% towards 2066–2070 due to temperature stress. Future soybean yields decreased by 1–13% due to temperature and moisture stresses. Future aggregated C4 crops produced higher yields compared to historical C4 yields. There were no differences between future aggregated and historical C3 crop yields. Both crop types were negatively affected by progressing climate change impacts towards the end of 2066–2070 simulation period. Reductions in future aggregated C3 crop yields ranged between 10–22%, and between 6–10% for C4 crops. We explained lower reductions in C4 compared to C3 crops due to a lesser degree of photorespiration, better water use efficiency, and better heat tolerance under conditions of high light intensities and increased temperatures in C4 crops. Irrigation resulted in increased future corn yields between 29–33%, and 3–38% of aggregated C4 crop yields, with no effect on soybean or aggregated C3 crop yields. In some regions, biochar applications caused significant yield reductions of 9.5–20% for corn, 5–7% for aggregated C3, and 3–5% for aggregated C4 crops, depending on the model. Yield reductions were ascribed to alterations in plant nutrient availability. It was concluded that under drier weather scenarios, irrigation may be a promising adaptation strategy for agriculture in the Southeastern US.

Changes in the phenolic compounds and antioxidant capacity of Berberis microphylla G. Forst. berries in relation to light intensity and fertilization

The objective of this study was to evaluate the qualitative and quantitative composition of the phenolic compounds and the antioxidant activity of B. microphylla fruit under different light intensities and levels of fertilization during two production years. Total monomeric anthocyanin concentration in high light intensity conditions was three times more than that obtained at medium light intensity, expressed for both fresh weight and dry weight terms (299.7mg/100g FFW and 9.5mg/g DFW, respectively). However, in the case of total polyphenol concentration, minor increases of 30 and 11% appeared under high light intensity in comparison with medium light intensity (906.6mg/100g FFW and 30.7mg/g DFW, respectively). Scavenging activity on DPPH was increased from 56.0 to 66.8% under the high light intensity treatment. This was also true for the reducing power which increased from 40 to 46.2%. Fertilizers reduced the flavonoid concentration, but increased the total polyphenol concentration at fertilization level 2. In the case of flavonoids, the maximum contents in fruits were 200.2 and 7.6mg (+)-catechin equivalents/100g FFW and DFW, respectively in the control treatment. The total polyphenol concentration was the highest (856.1 and 31.2mg tannic acid equivalents/g FFW and DFW, respectively) with the level fertilization 2. The scavenging activity on DPPH was from 60.3 to 62.8% when raising the fertilization level from 0 to 2, while the reducing power varied between 40.5 and 44.3% at levels 1 and 2. The total monomeric anthocyanin concentration increased with the level of fertilization in the fruits of plants at high light intensity, whereas the trend was inversed in those under medium light intensity. Hence, these studies display the possibility for maximizing both the productivity and the antioxidant capacity of fruits by crop management.

Arabidopsis thaliana FLO2 is Involved in Efficiency of Photoassimilate Translocation, Which is Associated with Leaf Growth and Aging, Yield of Seeds and Seed Quality.

FLO2, FLOURY ENDOSPERM 2, is highly conserved in higher plants, and rice FLO2 has been predicted to be involved in regulation of accumulation of storage compounds. We analyzed the function of Arabidopsis thaliana FLO2 (AtFLO2) because A. thaliana set structurally different seeds from those of rice. Although the flo2 mutant of A. thaliana showed normal germination, inflorescence and morphogenesis of flowers, peculiar phenotypes on leaves and siliques were observed, suggesting that this gene played important roles during both the vegetative and reproductive stages. The mutant leaves showed a decrease in chloroplast numbers, and increased total biomass with faster growth. When grown in high light intensity conditions, it was observed that aging events were induced. The flo2 mutant showed depressed transportation of photoassimilates into the sink organs. In the reproductive stage, the flo2 mutant had significantly smaller size siliques, causing a reduced yield of seeds. These seeds were structurally weak, and the quality of seeds was significantly lowered, with reduction of accumulation of storage compounds by seeds. A positron-emitting tracer imaging system (PETIS) analysis detected a decreased amount of photoassimilate transport in the flo2 mutant. Therefore, it was presumed that the phenotypes of the flo2 mutant were caused by reduced performance of translocation or transportation of the photoassimilates. Our observation suggests that AtFLO2 is strongly involved in regulation of translocation and transport of assimilates, and contributes greatly to quality control of the various processes involving substance supply or transfer, such as photoassimilation, leaf enlargement, yield of seeds in a silique and accumulation of seed storage compounds.

Photosynthetic performance of soybean plants to water deficit under high and low light intensity

The two major challenges to relay strip intercropping soybean production in Southwest China are drought and low light intensity. This study tests whether the impact of drought on the photosynthetic performance of soybean plants is different between low and high light intensity conditions. To investigate this, soybean plants were grown in pots in a factorial experiment at two irrigation regimes (75±2% and 45±2% of soil field capacity) and two light intensity treatments (100% and 65% light intensity) in 2011. In 2012, soybean plants were grown in two irrigation regimes (75±2% of soil field capacity vs. progressive soil drying) and two light intensity treatments (sole cropping soybean and relay strip intercropping soybean). Photosynthetic performance was assessed by measuring parameters such as net photosynthetic rate (Pn), stomatal conductance (Gs), water use efficiency (WUE), which were decreased significantly in drought stressed plants. We also observed differences in the photosynthetic responses of soybean plants to drought depending on the light intensity treatment the plants were subjected to. Shaded soybean plants in response to drought conditions had increased chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll (Chl), carotenoid (Car), ratio of Car/Chl, leaf relative water content (RLWC), leaf area per plant, specific leaf area (SLA), Pn, Gs, intercellular CO2 concentration (Ci), transpiration rate (Tr), photochemical quenching (qP) and electron transport rate (ETR). The above-mentioned photosynthetic changes may play an important role in determining how shaded soybean plants adjust their photosynthetic rate when experiencing drought conditions.

Redox-Dependent Modulation of Anthocyanin Biosynthesis by the TCP Transcription Factor TCP15 during Exposure to High Light Intensity Conditions in Arabidopsis.

TCP proteins integrate a family of transcription factors involved in the regulation of developmental processes and hormone responses. It has been shown that most members of class I, one of the two classes in which the TCP family is divided, contain a conserved Cys that leads to inhibition of DNA binding when oxidized. In this work, we describe that the class-I TCP protein TCP15 inhibits anthocyanin accumulation during exposure of plants to high light intensity by modulating the expression of transcription factors involved in the induction of anthocyanin biosynthesis genes, as suggested by the study of plants that express TCP15 from the 35SCaMV promoter and mutants in TCP15 and the related gene TCP14. In addition, the effect of TCP15 on anthocyanin accumulation is lost after prolonged incubation under high light intensity conditions. We provide evidence that this is due to inactivation of TCP15 by oxidation of Cys-20 of the TCP domain. Thus, redox modulation of TCP15 activity in vivo by high light intensity may serve to adjust anthocyanin accumulation to the duration of exposure to high irradiation conditions.

SGRL can regulate chlorophyll metabolism and contributes to normal plant growth and development in Pisum sativum L.

Among a set of genes in pea (Pisum sativum L.) that were induced under drought-stress growth conditions, one encoded a protein with significant similarity to a regulator of chlorophyll catabolism, SGR. This gene, SGRL, is distinct from SGR in genomic location, encoded carboxy-terminal motif, and expression through plant and seed development. Divergence of the two encoded proteins is associated with a loss of similarity in intron/exon gene structure. Transient expression of SGRL in leaves of Nicotianabenthamiana promoted the degradation of chlorophyll, in a manner that was distinct from that shown by SGR. Removal of a predicted transmembrane domain from SGRL reduced its activity in transient expression assays, although variants with and without this domain reduced SGR-induced chlorophyll degradation, indicating that the effects of the two proteins are not additive. The combined data suggest that the function of SGRL during growth and development is in chlorophyll re-cycling, and its mode of action is distinct from that of SGR. Studies of pea sgrL mutants revealed that plants had significantly lower stature and yield, a likely consequence of reduced photosynthetic efficiencies in mutant compared with control plants under conditions of high light intensity.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-015-0372-4) contains supplementary material, which is available to authorized users.