White Light Treatment Research Articles

Comprehensive insights into the influence of supplemental green light on the photosynthesis of ginger (Zingiber officinale Roscoe).

Although green light is not considered to contribute to the photosynthesis of plants, the photosynthesis of ginger, a dual-purpose vegetable used as a medicine and food, is affected by the green wave band. In this study, the supplementary green band of sunlight (SG) increased the net photosynthetic rate (Pn), maximal photochemical efficiency of PSII (Fv/Fm), and actual photochemical efficiency of PSII (Y(II)) compared with the sunlight treatment (S). The Pn and Fv/Fm of the SG treatment were higher than those of the white light (W) treatment, while the Pn and Fv/Fm of the green light (G) treatment alone were lower than those of the W treatment. Further analysis found that the minimal fluorescence (Fo) of the S treatment increased, especially at noon, while the Fo of the SG treatment decreased. Similarly, the Fo of the W treatment increased significantly, while the Fo of the white-green mixed light (WG) treatment decreased. The relative fluorescence values of the K-J-I bands in the SG and WG treatments were lower than those in the S and W treatments, respectively. The photochemical quenching (qP) of the WG treatment was higher than that of the W treatment, while the primary thermal losses corresponded to the sum of nonregulated heat dissipation and fluorescence emission (Y(NO)) of the WG treatment was lower than that of the W treatment. The SG treatment reduced the accumulation of plastoglobules but increased the accumulation of starch granules and leaf thickness. Moreover, the green band supplemented with white light significantly increased the biomass of the aboveground plant parts and promoted the active growth of the aboveground parts. Supplementing green light plays a regulatory role in ginger based on the following four points. First, it effectively promotes the transfer of electrons between the acceptor side of photosystem II; second, it optimizes ginger photosynthesis; third, it alleviates strong light stress by reducing the accumulation of reactive oxygen species; and fourth, it promotes heat dissipation and reduces the rapid burst of active oxygen in the chloroplast caused by excess energy. In summary, green light can significantly optimize the photosynthetic characteristics of ginger.

Objective light exposure measurements and circadian rhythm in patients with erythropoietic protoporphyria: A case-control study.

Erythropoietic protoporphyria (EPP) patients suffer from painful phototoxicity. Sunlight-avoiding behaviour has not yet been quantified objectively in EPP patients. To study total white light exposure obtained with an actigraph device, before and during afamelanotide treatment, in EPP patients compared to healthy controls. Effects on circadian rhythm, pain and sleep were also investigated. Adult EPP patients visiting the Porphyria Center Rotterdam of the Erasmus MC were included in this single-center longitudinal case-control open-label intervention study. Controls were age and place of residence matched. Participants wore an actigraph (Actiwatch Pro) during two weeks for multiple periods. Afamelanotide was given to EPP patients as part of standard care. Twenty-six EPP patients and 23 matched controls participated. Controls were statistically significantly more exposed to white light than EPP patients off treatment during autumn (95.4%), spring (69.9%), and summer (105.4%; p=0.01). EPP patients on afamelanotide treatment had 71.6% more light exposure during spring compared to EPP patients off treatment (p<0.01). Afamelanotide treatment resulted in a reduction of painful moments in the morning (6.5% decrease) and the evening (8.1% decrease; p<0.05). Bedtime differed between EPP patients off treatment, controls and EPP patients on treatment (23:45h±1:51 versus 23:02±1:41 and 23:14±1:29, respectively; p<0.0001). Actigraphy is a useful method to objectively measure white light exposure and treatment effects in EPP. In EPP patients afamelanotide treatment is associated with increased white light exposure during spring, and overall less pain. Treatment with afamelanotide is also associated with normalization of circadian rhythm.

Effects of The Proportion of The LED Light Red, Blue, and White Colors on Chlorophyll Content and Canopy Area of Pakcoy (Brassica rapa L.)

Abstract&#x0D; Light is the main energy source for plants for the photosynthesis process. In indoor cultivation systems (plant factories), LEDs can be used as artificial light. The dominant light colors absorbed by plants for the photosynthesis process are red and blue, but the proportion of the LED colors used is unknown, so it is necessary to research the proportions of light colors. This study aims to determine the effect of the proportions of red, blue, and white light on the chlorophyll content (SPAD value) and the canopy area of Pakcoy. Pakcoy was planted in a growth chamber and given seven different proportions of light for 12 hours with a lamp total of 60 Watt and light intensity of 2000 lux. This study was conducted for 49 days, and the observations to make once a week. The results showed the proportion of red, blue, and white LED light treatment affects the chlorophyll content and canopy area. The proportions of LED light 30 Watt red, 20 Watt blue, and 10 Watt white produced the highest chlorophyll content (35.0 SPAD value) and canopy area (70.7 cm2). In conclusion, the proportion of red, blue, and white LED light showed significantly different in the growth of Pakcoy.

Stable Reference Gene Selection for qRT-PCR Normalization in Strawberry (Fragaria × ananassa) Leaves under Different Stress and Light-Quality Conditions

Selecting an appropriate reference gene is of crucial importance for improving the accuracy of qRT-PCR analyses. In this study, strawberry (Fragaria ananassa) seedlings were subjected to different environmental conditions including heat, cold, drought, salt, white-light, blue-light, and red-light treatments. The expression levels of seven candidate reference genes, including Fa18S, FaGAPDH, FaPIRUV, FaDBP, FaHISTH4, FaACTIN1, and FaACTIN2, in the strawberry leaves were measured by qRT-PCR. Then, four programs (geNorm, NormFinder, BestKeeper, and RefFinder) were employed as tools to evaluate the expression stability of the candidate reference genes. The results showed that the expression stability of the reference genes varied under different conditions. For the cold stress and white-light treatments, FaACTIN2 was evaluated to be the most stable reference gene. FaGAPDH should be used as the reference gene under salt-stress condition and red-light treatment. For the data normalization under drought-stress treatment, FaDBP is the recommended reference gene with the highest expression stability. FaHISTH4 was observed to be the best reference gene for data normalization under heat stress and blue-light treatment. This work provides information on selecting reference genes for accurate gene expression analyses of target genes in strawberry leaves under various abiotic stress and light-quality conditions.

Influence of light quality on growth and secondary metabolite in tissue cultures of Gardenia jasmonides, Variegata

The influence of white, blue and red Light-Emitting Diodes (LED) on the growth and the secondary metabolites production in calli and shoots cultures of Gardenia jasmonides, Variegata was evaluated. The white light generally has a powerful effect on both fresh and dry weights of the two types of cultures. White light treatment recorded (11.88 and 0.63 g) for the fresh and dry weight (in case of calli) followed by the blue light which recorded (11.78 and 0.60 g ), respectively. The extracts of shoots exposed to white LED light recorded the highest reducing efficiency (74.40 %). It could be justified as the shoots that exposed to the white light recorded the highest cholorogenic acid (CGA) compared to all the other treatments. Among different phenolic and flavonoids compounds which were tested in the calli and shoots cultures exposed to the different LED light quality, only the chlorogenic acid was detected in the different treatments in both cultures with varying quantities. The white LED light recorded the highest content of chlorogenic acid with both cultures, since it scored 52.43 µg / gdw with calli cultures versus 8783.53 µg / gdw with shoots cultures.

The Influence of Different Light Wavelengths of Anthropogenic Light at Night on Nestling Development and the Timing of Post-fledge Movements in a Migratory Songbird

Many different aspects of an animal’s lifecycle such as its behavior, patterns of hormone activity, and internal clock time, can be affected by anthropogenic light at night (ALAN). Exposing an organism to ALAN during its early life could also have an impact on its development. Since photoperiod can trigger or schedule the migration timing of long-distance migratory birds, there is great potential for anthropogenic light to interact with photoperiod to affect timing. However, very little has been investigated regarding the impacts of ALAN on post-hatching development and migration timing. We investigated the impact of ALAN during nestling development in a long-distance migratory songbird to determine the potential impact on the timing of post-breeding movements in the wild. We experimentally manipulated the light by using programmable lighting, in the nest boxes of free-living nestlings of purple martin (Progne subis) in Manitoba, Canada. We exposed two groups of developing nestlings, from hatch to fledge date, to green or white LED lights (5 lux) during the night. We also included a control group that experienced natural, ambient light at night. We found that some adults abandoned their nests shortly after starting the experiment (4 of 15 nests in the white light treatment). For the nests that remained active, nestlings exposed to the white light treatment had higher weights (at day 20 or 22), later fledge dates (1.54 ± 0.37, 95% CI 0.80–2.28), and later colony departure date (2.84 ± 1.00, 95% CI 0.88–4.81), than young of the control group. Moreover, nestlings of both white and green light groups had longer nesting duration than nestlings of the control group. This study demonstrates the impact of ALAN on the development of post-breeding movement timing in nestlings of wild migratory birds. However, our results also indicate that green light may have less of an impact as compared to white light.

Non-destructive in Situ Measurement of Aquaponic Lettuce Leaf Photosynthetic Pigments and Nutrient Concentration Using Hybrid Genetic Programming

Phytopigment and nutrient concentration determination normally rely on laboratory chemical analysis. However, non-destructive and onsite measurements are necessary for intelligent closed environment agricultural systems. In this study, the impact of photosynthetic light treatments on aquaponic lettuce leaf canopy (Lactuca sativa var. Altima) was evaluated using UV-Vis spectrophotometry (300-800 nm), fourier transform infrared spectroscopy (4000-500 per cm), and the integrated computer vision and computational intelligence. Hybrid decision tree and multigene symbolic regression genetic programming (DT-MSRGP) exhibited the highest predictive accuracies of 80.9%, 89.9%, 83.5%, 85.5%, 81.3%, and 83.4% for chlorophylls a and b, β-carotene, anthocyanin, lutein, and vitamin C concentrations present in lettuce leaf canopy based on spectro-textural-morphological signatures. An increase in β-carotene and anthocyanin concentrations verified that these molecular pigments act as a natural sunscreen to protect lettuce from light stress and an increase in chlorophylls a and b ratio in the white light treatment corresponds to reduced emphasis on photon energy absorbance in chloroplast photosystem II. Red-blue light induces chlorophyll b concentration while white light promotes all other pigments and vitamin C. It was confirmed that the use of the DT-MSRGP model is essential as the concentration of phytopigment and nutrients significantly change during the head development and harvest stages.

Effects of White and Red Light Photoperiods on Physiology and Biochemistry as well as Glucoraphanin Metabololism of Broccoli Sprouts

In this study, the effects of white light and red light at different photoperiods (0, 4, 8, 12, 16 and 20 h·d−1) on growth, contents of soluble sugar, soluble protein, ascorbic acid, anthocyanins as well as glucoraphanin metabolism of broccoli sprouts were studied. The results showed that the growth of broccoli sprouts was inhibited by light treatment, but red light promoted the growth compared with white light. With the increasing of light photoperiods, the content of soluble sugar, soluble protein, ascorbic acid, glucoraphanin and total glucosinolates, myrosinase activity as well as sulforaphane formation firstly increased, then decreased. Compared with white light, red light significantly enhanced soluble sugar, soluble protein, ascorbic acid and glucoraphanin content in broccoli sprouts. However, higher anthocyanin content was observed in white light treated broccoli sprouts rather than red light treated broccoli sprouts. In addition, when photoperiod was less than 12 h, red light resulted in higher sulforaphane formation than white light (P<0.05). When photoperiod was more than 12 h, red light did not affect even decreased sulforaphane formation compared with white light treatment. In conclusion, red light treatment was beneficial to the enhancement of yield and nutritional quality of broccoli sprouts compared with white light, and 12 h·d−1 was the appropriate photoperiods.

Effect of physical and chemical treatments on breaking the seed dormancy of Caesalpinia bonduc (L.) Roxb.

Caesalpinia bonduc (L.) Roxb. is a medicinal plant belonging to the family Caesalpiniaceae was used for the present study. It is a prickly shrub widely distributed all over the world. Keeping the economic and social medicinal uses of C. bonduc seeds are being used widely in Folk, Ayurvedha, Siddha, Unani medicines to treat skin disease, eyesores, cancer, asthma, tuberculorosis, fever, toothaches etc. The aim of this study is to determine the requirements for breaking seed dormancy and germination of C. bonduc. The germination is prevented due to hard seed coat. C. bonduc seeds were experimented with various physical and chemical treatments to break the dormancy. The seeds were subjected to various treatments like mechanical scarification, dry heat method, light, hot water, acid scarification, inorganic compounds, plant growth regulators etc. The seeds treatment with mechanical scarification at 50, 40 and 30 seconds showed 100%, 80% and 10% of germination, whereas no changes was observed in dry heat. White light treatment showed 100% germination at 48 hrs, whereas darkness and red light showed least germination of about 10%. The hot-water treatment showed 100% germination. In chemical treatments, concentrated sulphuric acid scarification showed highest germination percentage, whereas lowest germination was found in nitric acid. Among the plant growth regulators, Gibberellic acid showed 100% germination whereas 2-isopentyl adenine showed least germination of 10% at 50 ppm. Results of this study prove that mechanical scarification was the most effective treatment to overcome dormancy of seeds in C. bonduc.

Providing colored photoperiodic light stimulation during incubation: 1. Effects on embryo development and hatching performance in broiler hatching eggs

Providing lighting schedule during incubation has been shown to improve chick quality and reduce stress posthatch. This study was conducted to evaluate the effects of providing light of different colors during incubation on embryo development, air cell temperature, the spread of hatch, and hatching performance. Four batches of eggs (n = 2,176, 1,664, 1,696 and 1,600) from Ross 308 broiler breeders were used in the experiment. In each trial, eggs were randomly distributed into 4 lighting treatments. The incubation lighting treatments included: incubated under dark as control, illuminated with white, red or blue lights for 12 h daily. There were no incubation lighting treatment differences in embryo development, the spread of hatch, hatchability, embryo mortality, hatch weight, chick length, navel closure quality, yolk-free body weight, or relative spleen weight. However, embryos incubated under red light had lower average air cell temperature than those in dark, white or blue light treatments. This finding may suggest higher melatonin secretion during the scotophase when illuminated with red light. Male chicks incubated under dark had a higher bursa of Fabricius weight than males illuminated with blue light. In conclusion, these results suggest that the red, white and blue light stimulation during incubation had no negative effects on hatchability, embryo mortality, spread of hatch or day-old chick quality, but may have potential impacts on immunity and energy metabolism in broiler embryos.

Transcriptome Profile Analysis of Strawberry Leaves Reveals Flowering Regulation under Blue Light Treatment.

Blue light is an important signal that regulates the flowering of strawberry plants. To reveal the mechanism of early flowering under blue light treatment at the transcriptional regulation level, seedlings of cultivated strawberry (Fragaria × ananassa Duch.) “Benihoppe” were subjected to a white light treatment (WL) and blue light treatment (BL) until their flowering. To detect the expression patterns of genes in response to BL, a transcriptome analysis was performed based on RNA-Seq. The results identified a total of 6875 differentially expressed genes (DEGs) that responded to BL, consisting of 3138 (45.64%) downregulated ones and 3737 (54.36%) upregulated ones. These DEGs were significantly enriched into 98 GO terms and 71 KEGG pathways based on gene function annotation. Among the DEGs, the expression levels of genes that might participate in light signaling (PhyB, PIFs, and HY5) and circadian rhythm (FKF1, CCA1, LHY, and CO) in plants were altered under BL. The BBX transcription factors which responded to BL were also identified. The result showed that the FaBBX29, one of strawberry's BBX family genes, may play an important role in flowering regulation. Our results provide a timely, comprehensive view and a reliable reference data resource for further study of flowering regulation under different light qualities.

Positive effect of timed blue-enriched white light on sleep and cognition in patients with mild and moderate Alzheimer\u2019s disease

Conflicting results have been reported regarding the effectiveness of light treatment (LT) in patients with Alzheimer’s disease (AD). We investigated the effectiveness of blue-enriched white LT on sleep, cognition, mood and behavior in patients with mild and moderate AD. The treatment group (n = 14) sat about 60 cm away from a small (136 × 73 × 16 mm) LED light box for 1 h each morning for 2 weeks. The control group (n = 11) wore dark, blue-attenuating sunglasses during the 1 h exposures. The morning light started 9–10 h after each individual’s dim light melatonin onset (DLMO). Assessments were done at baseline (T0), immediate post-treatment (T1), and 4 weeks after the end of the 2 weeks of LT (T2). Sleep was measured by actigraphy. Blue-enriched LT had a significantly better effect on the Pittsburgh Sleep Quality Index at T2 compared to blue-attenuated LT, and a trend of better effectiveness on total sleep time at T2. There was a significant increase in Mini-Mental State Examination score at T2 after blue-enriched LT than that at T0. Our findings suggest that morning blue-enriched LT has a benefit in improving sleep and cognitive function in AD patients.

The Impact of Far-Red Light Supplementation on Hormonal Responses to Cold Acclimation in Barley.

Cold acclimation, the necessary prerequisite for promotion of freezing tolerance, is affected by both low temperature and enhanced far-red/red light (FR/R) ratio. The impact of FR supplementation to white light, created by artificial LED light sources, on the hormone levels, metabolism, and expression of the key hormone metabolism-related genes was determined in winter barley at moderate (15 °C) and low (5 °C) temperature. FR-enhanced freezing tolerance at 15 °C was associated with promotion of abscisic acid (ABA) levels, and accompanied by a moderate increase in indole-3-acetic acid (IAA) and cis-zeatin levels. The most prominent impact on the plants’ freezing tolerance was found after FR pre-treatment at 15 °C (for 10 days) followed by cold treatment at FR supplementation (7 days). The response of ABA was diminished in comparison with white light treatment, probably due to the elevation of stress tolerance during FR pre-treatment. Jasmonic acid (JA) and salicylic acid (SA) were transiently reduced. When the plants were exposed directly to a combination of cold (5 °C) and FR supplementation, ABA increase was higher than in white light, and was associated with enhanced elevation of JA and, in the longer term (after 7 days), with IAA and cis-zeatin increase, which indicates a stronger stress response and better acclimation. Cold hardening was more efficient when FR light was applied in the early developmental stage of the barley plants (three-leaf stage, 18 days), rather than in later stages (28-days). The dynamics of the phytohormone changes are well supported by the expression profiles of the key hormone metabolism-related genes. This series of treatments serves as evidence for the close relationship between plant hormones, light quality, and low temperature at the beginning of cold acclimation. Besides the timing of the FR treatments, plant age also represents a key factor during light spectrum-dependent cold acclimation.

OsRR6, a type-A response regulator in rice, mediates cytokinin, light and stress responses when over-expressed in Arabidopsis

Plants have evolved a complex network of components that sense and respond to diverse signals. In the present study, we have characterized OsRR6, a type-A response regulator, which is part of the two-component sensor-regulator machinery in rice. The expression of OsRR6 is induced by exogenous cytokinin and various abiotic stress treatments, including drought, cold and salinity stress. Organ-specific expression analysis revealed that its expression is high in anther and low in shoot apical meristem. The Arabidopsis plants constitutively expressing OsRR6 (OsRR6OX) exhibited reduced cytokinin sensitivity, adventitious root formation and enhanced anthocyanin accumulation in seeds. OsRR6OX plants were more tolerant to drought and salinity conditions when compared to wild-type. The hypocotyl growth in OsRR6OX seedlings was significantly inhibited under red, far-red and blue-light conditions and also a decline in transcript levels of OsRR6 was observed in rice under the above monochromatic as well as white light treatments. Transcriptome profiling revealed that the genes associated with defense responses and anthocyanin metabolism are up-regulated in OsRR6OX seedlings. Comparative transcriptome analysis showed that the genes associated with phenylpropanoid and triterpenoid biosynthesis are enriched among differentially expressed genes in OsRR6OX seedlings of Arabidopsis, which is in conformity with reanalysis of the transcriptome data performed in rice transgenics for OsRR6. Further, genes like DREB1A/CBF3, COR15A, KIN1, ERD10 and RD29A are significantly upregulated in OsRR6OX seedlings when subjected to ABA and abiotic stress treatments. Thus, a negative regulator of cytokinin signaling, OsRR6, plays a positive role in imparting abiotic stress tolerance.

Comparison of the effects of LED light quality combination on growth and nutrient accumulation in green onion (Allium fistulosum L.).

The growth and development and metabolism of plants have different physiological responses to different light qualities. To study the influence of light qualities on green onions, the impacts of LED light treatment on the growth and development as well as the nutritional components and flavor substances in green onions were studied under controlled conditions. Leaf area, plant height, dry matter accumulation, Dickson's quality index (DQI), nutritional content, and volatile compounds under different light quality treatments were determined. The results indicated that the white and blue combined light (W/B: 3/1) treatment was the most beneficial to growth and nutrient accumulation and led to higher levels of sulfur compounds in the green onions than the other treatments. This shows that it is possible to control the contents of compounds that affect consumer preferences by adjusting the lighting conditions and to thereby increase the value and quality of seasoning vegetables.

Are Yellow Sticky Cards and Light Traps Effective on Tea Green Leafhoppers and Their Predators in Chinese Tea Plantations?

Simple SummaryLeafhoppers are serious insect pests in agriculture across the world. Both nymphs and adults suck the sap of plant shoots and leaves with their piercing–sucking mouthparts causing damage called “hopperburn”. The tea green leafhopper, Empoasca onukii, is one of most damaging pests in tea plantations in Asia. In China, yellow sticky cards and light traps are increasingly used to control leafhoppers in tea plantations, especially the tea green leafhopper. Visually, several leafhoppers appear to be captured and killed, however, the real control efficiency and the damage to natural enemies remains unclear. In our study, a 16-week open field experiment with daily weather monitoring was designed to test the responses of tea green leafhopper, parasitoids and spiders to yellow sticky cards and light traps (cover with sticky cards) that used different light colours. An exclosure experiment was also designed to further test the influence of the three light systems (without sticky card) on the same groups of species. The results suggested that light, especially green and white, can be useful as a way to control leafhopper populations without affecting parasitoids and spiders too much.In Chinese tea plantations, yellow sticky cards and light traps are increasingly used to control insect pests, especially the tea green leafhopper Empoasca onukii. In this study, a 16-week open-field experiment with daily weather monitoring was designed to test the responses of tea green leafhopper, parasitoids and spiders to yellow sticky cards and three light traps with different wavelengths (covered with sticky cards). An exclosure experiment was also designed to further test the influence of the three light systems (without sticky card) on the same species. The results showed that all three light emitting diode (LED) light traps (white, green and yellow) and yellow sticky cards attracted many more E. onukii male adults than females during the course of the open field experiment, with less than 25% of trapped adults being females. Parasitoids and spiders were also attracted by these systems. Weather variables, especially rainfall, influenced the trapping efficiency. In the exclosure experiment, the population of leafhoppers in the yellow sticky card treatment did not decline significantly, but the number of spiders significantly decreased. The green and white light treatments without sticky cards showed a significant control of E. onukii and no obvious harm to spiders. These results suggest that yellow sticky cards and light traps have limited capacity to control tea green leafhoppers. However, light, especially green light, may be a promising population control measure for tea green leafhoppers, not as killing agents in the traps, but rather as a behavioral control system.

Effects of Light-Emitting Diodes on the Accumulation of Phenolic Compounds and Glucosinolates in Brassica juncea Sprouts

Recent improvements in light-emitting diode (LED) technology afford an excellent opportunity to investigate the relationship between different light sources and plant metabolites. Accordingly, the goal of the present study was to determine the effect of different LED (white, blue, and red) treatments on the contents of glucosinolates (glucoiberin, gluconapin, sinigrin, gluconasturtiin, 4-methoxyglucobrassicin, 4-hydroxyglucobrassicin, glucobrassicin, and neoglucobrassicin) and phenolic compounds (4-hydroxybenzonate, catechin, chlorogenic acid, caffeate, gallate, sinapate, and quercetin) in Brassica juncea sprouts. The sprouts were grown in a growth chamber at 25 °C under irradiation with white, blue, or red LED with a flux rate of 90 μmol·m−2·s−1 and a long-day photoperiod (16 h light/8 h dark cycle). Marked differences in desulfoglucosinolate contents were observed in response to treatment with different LEDs and different treatment durations. In addition, the highest total desulfoglucosinolate content was observed in response to white LED light treatment, followed by treatment with red LED light, and then blue LED light. Among the individual desulfoglucosinolates identified in the sprouts, sinigrin exhibited the highest content, which was observed after three weeks of white LED light treatment. The highest total phenolic contents were recorded after one week of white and blue LED light treatment, whereas blue LED irradiation increased the production of most of the phenolic compounds identified, including 4-hydroxybenzonate, gallate, sinapate, caffeate, quercetin, and chlorogenic acid. The production of phenolics decreased gradually with increasing duration of LED light treatment, whereas anthocyanin accumulation showed a progressive increase during the treatment. These findings indicate that white LED light is appropriate for glucosinolate accumulation, whereas blue LED light is effective in increasing the production of phenolic compounds in B. juncea sprouts.

Systematic Identification of the Light-quality Responding Anthocyanin Synthesis-related Transcripts in Petunia Petals

Previous studies have shown that high light intensity can induce anthocyanin synthesis (AS) in petunia plants. To identify which kind of light quality plays a role in inducing such metabolic process, and what transcripts participate in controlling it, we carried out whole-transcriptome sequencing and analysis of petunia petals treated with different light-quality conditions. Among the red and white light treatments, a total of 2 205 differentially expressed genes and 15, 22, and 20 differentially expressed circRNAs, miRNAs, and lncRNAs, were identified respectively. The AS-related genes, including the structural genes CHSj, F3′H, F3′5′H, DFR, and ANS, and the regulatory genes AN4, DPL, PHZ and MYBx were found to be downregulated under red light condition compared with their levels under white light condition. Furthermore, the light photoreceptor Cryptochrome 3 (CRY3) and a series of light-dependent genes, such as PIF, HY5, and BBXs, were also determined to respond to the light treatments. The anthocyanin contents in early petunia petals under red light were significantly lower than that under white and blue light. The results of qRT-PCR further confirmed the expression pattern of some AS-related and light-response genes in response to different light quality. Yeast two-hybrid results showed that the key elements in the light signal pathway, HY5 can interact with BBX19, BBX24 and BBX25. And PHZ, the important AS regulator can induce anthocyanin synthesis in response to blue light quality from transient expression analysis in petunia petals. These findings presented here not only deepen our understanding of how light quality controls anthocyanin synthesis, but also allow us to explore potential target genes for improving pigment production in petunia flower petals.

Blue LED light promotes indican accumulation and flowering in indigo plant, Polygonum tinctorium

The photoperiod is a day-length-dependent seasonal change of physiological or developmental activities, such as flowering, in many plant species. Polygonum tinctorium (P. tinctorium) is an important industrial crop producing indigo blue dyes, and indican is an important substance as a precursor of indigo. Here, we report the day-length-dependent responses of growth, flowering, and indican synthesis in P. tinctorium. Indigo plants were grown in a hydroponic system under artificial light conditions in a completely-controlled plant factory. The growth parameters and indican content of leaves were measured and compared. Certain growth parameters (such as fresh weight and number of leaves) under 24-h continuous irradiation were significantly higher than those under other day-length conditions. Under 12-h photoperiod conditions, the flowering rate of plants with blue LED treatment increased six-fold compared with fluorescent white light treatment, while none of the plants flowered with red LED treatment. In the leaves, the relative expression levels of Pt’IGS and Pt’BGL were significantly higher in newer leaves compared to older ones. Indican content was greatly enhanced by blue light under 24-h continuous irradiation, which was reflected by increased expression levels of Pt’IGS. These findings demonstrate that there is a new regulatory mechanism for the indican synthesis pathway through blue light signalling. Blue light provides feasible strategy for artificially regulating indican synthesis and flowering in P. tinctorium.

The degradation of chloroplast components during postharvest senescence of broccoli florets is delayed by low-intensity visible light pulses

Abstract Senescence in harvested green organs, such as broccoli inflorescences, is a highly regulated process characterized by a massive degradation of chloroplast components. The dismantling of the chloroplast involves small “senescence-associated vacuoles” (SAVs) with high protease activity. The expression of the senescence associated gene, SAG12 (here BoSAG12), which encodes a senescence associated cysteine protease, correlated with SAVs appearance. One environmental factor that delays senescence is low-intensity visible light. Daily irradiation with pulses of 2 h of low-intensity white light (20–25 μmol m−2 s−1) is a promising technology to delay postharvest senescence of broccoli stored at room temperature. The aim of this study was to analyze the effects of low-intensity white (W) and red (R) light treatments on some events related to chloroplast dismantling during postharvest senescence of broccoli inflorescences. We detected that chloroplasts number did not change during postharvest senescence. We found that SAVs participate in the dismantling of chloroplasts during the postharvest senescence of broccoli florets. SAVs appearance occurred earlier than visible yellowing. The two light treatments used, i.e. pulses of low-intensity W and R light, delayed chloroplast changes, including chlorophyll degradation and SAVs appearance. The delay of SAVs appearance was accompanied by the delay of BoSAG12 induction in broccoli florets. Regarding protein degradation, not all proteins analyzed were affected equally. The light treatments had greater effect on the retention of thylakoid proteins than on Rubisco and apparently, the effects of light treatment were higher on proteins from PSII (LHCII) than on those from PSI (LHCI and PsaA).