Cryptochromes in the field: how blue light influences crop development

Synergistic effects of selenium nanoparticles and LED light on enhancement of secondary metabolites in sandalwood (Santalum album) plants through in-vitro callus culturing technique

The yield and concentration of secondary metabolites (SMs) in plants can vary due to numerous challenges such as dynamic environmental conditions, moisture, soil quality, soil organic matter and plant genetics. To obtain a good yield of SMs novel elicitation approaches, such as the use of biotic and abiotic stressors, genetic modifications, and optimized growth conditions, have been practiced, particularly the use of selenium nanoparticles (SeNPs) and light emitting diode (LED) interaction through employing tissue culture technique. In the present study, in vitro callus cultures of sandalwood (Santalum album L.) were subjected to elicitation with different concentrations of SeNPs with doses of 30 µg/L, 60 µg/L, and 90 µg/L in combination with green (∼550 nm), red (∼660 nm) and blue (∼460 nm) LED lights. Interaction of these treatments produced 16 treatments replicated three times in 48 test tubes. The results were analysed using two-way ANOVA and Tukey's HSD test. The study revealed that synergistic interaction between SeNPs and LED light wavelengths significantly enhanced callus growth and secondary metabolite (SM) production eliciting callus cultures with blue LED light and a dose of 90 µg/L SeNPs resulted in an increase in callus growth including fresh weight, dry weight, and the number of shoot branches per callus. This combined treatment positively influenced the functions of major bioactive antioxidants such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and phenylalanine ammonia-lyase (PAL). Furthermore, the concentrations of essential secondary metabolites, including total phenolic, total saponins, casein/BSA/PVPP-bound tannins, flavan-3-ols, and tocopherols experienced substantial elevation under the synergistic influence of SeNPs and LED light conditions. The sandalwood plants produced through the callus culturing technique using optimized SeNPs and LED lights show an enhanced yield of secondary metabolites, which will be very useful and potential for pharmaceutical, cosmetic and various other industries to discover and develop novel products.

Effect of Light Quality on the seed Germination and Development of Coffee Seedlings (Coffea arabica)

Coffee (Coffea arabica) cultivation is vital to the global economic, social and cultural life of farmers. However, senescent and disease-susceptible plantations affect coffee productivity. Therefore, it is crucial to improve biotechnological strategies such as micropropagation to increase the number of plants for replanting. In this study, the dark condition (T1) and different light qualities (T0-white light 400-700 nm; T2-red light 660 nm and T3-blue light 460 nm) were evaluated to optimize the in vitro propagation of 4 and 9 month-old coffee seeds. The results showed that red light had the highest percentage, an outstanding germination rate index, which may suggest that in the case of coffee seeds could be involved phytochromes that promote germination in a red light quality. In summary, the ideal conditions for in vitro micropropagation of coffee are under white and red light condition.

The growth, nutrient uptake and fruit quality in four strawberry cultivars under different Spectra of LED supplemental light

An experiment was conducted in a greenhouse to determine the effects of different supplemental light spectra on the growth, nutrient uptake, and fruit quality of four strawberry cultivars. The plants were grown under natural light and treated with blue (460 nm), red (660 nm), and red/blue (3:1) lights. Results showed that the "Parous" and "Camarosa" had higher fresh and dry mass of leaves, roots, and crowns compared to the "Sabrina" and "Albion". The use of artificial LED lights improved the vegetative growth of strawberry plants. All three supplemental light spectra significantly increased the early fruit yield of cultivars except for "Parous". The red/blue supplemental light spectrum also increased the fruit mass and length of the "Albion". Supplemental light increased the total chlorophyll in "Camarosa" and "Albion", as well as the total soluble solids in fruits. The "Albion" had the highest concentration of fruit anthocyanin, while the "Sabrina" had the lowest. The use of supplemental light spectra significantly increased the fruit anthocyanin concentration in all cultivars. Without supplemental light, the "Camarosa" had the lowest concentration of K and Mg, which increased to the highest concentration with the use of supplemental light spectra. All three spectra increased Fe concentration to the highest value in the "Sabrina", while only the red/blue light spectrum was effective on the "Camarosa". In conclusion, the use of supplemental light can increase the yield and fruit quality of strawberries by elevating nutrients, chlorophyll, and anthocyanin concentrations in plants.

'Seeing' the electromagnetic spectrum: spotlight on the cryptochrome photocycle

Cryptochromes are widely dispersed flavoprotein photoreceptors that regulate numerous developmental responses to light in plants, as well as to stress and entrainment of the circadian clock in animals and humans. All cryptochromes are closely related to an ancient family of light-absorbing flavoenzymes known as photolyases, which use light as an energy source for DNA repair but themselves have no light sensing role. Here we review the means by which plant cryptochromes acquired a light sensing function. This transition involved subtle changes within the flavin binding pocket which gave rise to a visual photocycle consisting of light-inducible and dark-reversible flavin redox state transitions. In this photocycle, light first triggers flavin reduction from an initial dark-adapted resting state (FADox). The reduced state is the biologically active or 'lit' state, correlating with biological activity. Subsequently, the photoreduced flavin reoxidises back to the dark adapted or 'resting' state. Because the rate of reoxidation determines the lifetime of the signaling state, it significantly modulates biological activity. As a consequence of this redox photocycle Crys respond to both the wavelength and the intensity of light, but are in addition regulated by factors such as temperature, oxygen concentration, and cellular metabolites that alter rates of flavin reoxidation even independently of light. Mechanistically, flavin reduction is correlated with conformational change in the protein, which is thought to mediate biological activity through interaction with biological signaling partners. In addition, a second, entirely independent signaling mechanism arises from the cryptochrome photocycle in the form of reactive oxygen species (ROS). These are synthesized during flavin reoxidation, are known mediators of biotic and abiotic stress responses, and have been linked to Cry biological activity in plants and animals. Additional special properties arising from the cryptochrome photocycle include responsivity to electromagnetic fields and their applications in optogenetics. Finally, innovations in methodology such as the use of Nitrogen Vacancy (NV) diamond centers to follow cryptochrome magnetic field sensitivity in vivo are discussed, as well as the potential for a whole new technology of 'magneto-genetics' for future applications in synthetic biology and medicine.

A Review of the Current State of Magnetic Force Microscopy to Unravel the Magnetic Properties of Nanomaterials Applied in Biological Systems and Future Directions for Quantum Technologies

Magnetism plays a pivotal role in many biological systems. However, the intensity of the magnetic forces exerted between magnetic bodies is usually low, which demands the development of ultra-sensitivity tools for proper sensing. In this framework, magnetic force microscopy (MFM) offers excellent lateral resolution and the possibility of conducting single-molecule studies like other single-probe microscopy (SPM) techniques. This comprehensive review attempts to describe the paramount importance of magnetic forces for biological applications by highlighting MFM's main advantages but also intrinsic limitations. While the working principles are described in depth, the article also focuses on novel micro- and nanofabrication procedures for MFM tips, which enhance the magnetic response signal of tested biomaterials compared to commercial nanoprobes. This work also depicts some relevant examples where MFM can quantitatively assess the magnetic performance of nanomaterials involved in biological systems, including magnetotactic bacteria, cryptochrome flavoproteins, and magnetic nanoparticles that can interact with animal tissues. Additionally, the most promising perspectives in this field are highlighted to make the reader aware of upcoming challenges when aiming toward quantum technologies.

The Role of Light Quality in Regulating Early Seedling Development

It is well-established that plants are sessile and photoautotrophic organisms that rely on light throughout their entire life cycle. Light quality (spectral composition) is especially important as it provides energy for photosynthesis and influences signaling pathways that regulate plant development in the complex process of photomorphogenesis. During previous years, significant progress has been made in light quality's physiological and biochemical effects on crops. However, understanding how light quality modulates plant growth and development remains a complex challenge. In this review, we provide an overview of the role of light quality in regulating the early development of plants, encompassing processes such as seed germination, seedling de-etiolation, and seedling establishment. These insights can be harnessed to improve production planning and crop quality by producing high-quality seedlings in plant factories and improving the theoretical framework for modern agriculture.

Photomorphogenesis and Photosynthetic Traits Changes in Rice Seedlings Responding to Red and Blue Light

The purpose of this study is to determine the effects of red and blue lights on the photomorphogenesis and photosynthetic traits of rice seedlings. The rice seedlings were cultured with red light (R), blue light (B), combined red and blue lights (R3B1/R1B1/R1B3), and white light (CK) as the control. The combined application of red and blue lights could promote the growth of rice seedlings to varying degrees; enhance photosynthesis by increasing the seedling leaf area, chlorophyll content, and chlorophyll fluorescence; improve root characteristics by increasing root number, root volume, and root activity; and thus increase the dry matter accumulation of rice seedlings. In addition, the combination of red and blue lights could regulate the expression of genes related to photosynthesis in rice leaves, affect the activity of the Rubisco enzyme, and then affect the photosynthesis of rice seedlings. These results indicate that red and blue lights have direct synergistic effects, which can regulate the growth of rice seedlings and promote the morphogenesis of rice seedlings. The combined application of red and blue lights can be used to supplement the light in rice-factory seedling raising.

Simultaneous Application of Red and Blue Light Regulate Carbon and Nitrogen Metabolism, Induces Antioxidant Defense System and Promote Growth in Rice Seedlings under Low Light Stress

The purpose of this study is to determine the effect of light quality on growth, carbon and nitrogen metabolism, and antioxidant defense system of rice seedlings. Six light conditions were employed, including white (W), red (R), blue (B), combined LED of R and B at 3:1 (R3B1), combined LED of R and B at 1:1 (R1B1), as well as combined LED of R and B at 1:3 (R1B3). Combined application of red light and blue light could promote the growth of rice seedling leaves and roots under low light stress to varying degrees, increase the photosynthetic area by increasing the leaf area, improve the root characteristics by increasing the root volume, and increase the dry matter accumulation of rice seedlings. In addition, the combination of red light and blue light could increase carbon and nitrogen metabolites in rice seedling leaves, regulate the expression of genes related to carbon and nitrogen metabolism and enzyme activity, and enhance the antioxidant enzyme activity of rice seedlings. These results indicate that red light and blue light directly have synergistic effects which can regulate the carbon and nitrogen metabolism of rice seedlings, promote the morphogenesis of rice seedlings under low light stress, and promote growth, which has never been reported in previous studies. This study is a new discovery in the application of light quality in crop production and provides new avenues to enhance crop stress resistance. However, further study is needed to explore the physio-biochemical and molecular mechanisms of light quality in crop production.

The red/blue light ratios from light-emitting diodes affect growth and flower quality of Hippeastrum hybridum 'Red Lion'

Light quality strongly impacts the growth and flower quality of ornamental plants. The optimum light quality for the growth and flowering of Hippeastrum remains to be validated. In the present study, we investigated the effect of the red/blue light ratio of LEDs on the growth and flowering quality of H. hybrid 'Red Lion'. Two LEDs with red/blue light ratio of 1:9 (R₁₀B₉₀) and 9:1 (R₉₀B₁₀) were designed. LEDs of white light were the control. In the earlier vegetative and reproductive growth phase, R₉₀B₁₀ increased the biomass of the bulbs, leaves, and flowers. Compared with the control and R₁₀B₉₀ group, R₉₀B₁₀ LEDs delayed flowering by 2.30 d and 3.26 d, respectively. Based on chlorophyll contents, photosynthetic capacity, chlorophyll fluorescence parameters, and carbohydrate contents, the photosynthesis rate was higher in the R₁₀B₉₀ group. Optimal red and blue light intensity promoted the accumulation of carbohydrates and early flowering and prolonged the flowering period of H. hybrid. Microscopic analysis showed that stomatal density was high, and the number of chloroplasts was large in the R₁₀B₉₀ treatment group, which enhanced photosynthesis. Particularly, R₁₀B₉₀ promoted the expression of seven key genes related to chlorophyll synthesis. R₁₀B₉₀ also promoted early overexpression of the HpCOL gene that promotes early flowering. Thus, higher blue light and 10% red light intensities promote early and extended flowering, while higher red light and 10% blue light promote vegetative plant growth but delay flowering.

Underlying Biochemical and Molecular Mechanisms for Seed Germination

With the burgeoning population of the world, the successful germination of seeds to achieve maximum crop production is very important. Seed germination is a precise balance of phytohormones, light, and temperature that induces endosperm decay. Abscisic acid and gibberellins—mainly with auxins, ethylene, and jasmonic and salicylic acid through interdependent molecular pathways—lead to the rupture of the seed testa, after which the radicle protrudes out and the endosperm provides nutrients according to its growing energy demand. The incident light wavelength and low and supra-optimal temperature modulates phytohormone signaling pathways that induce the synthesis of ROS, which results in the maintenance of seed dormancy and germination. In this review, we have summarized in detail the biochemical and molecular processes occurring in the seed that lead to the germination of the seed. Moreover, an accurate explanation in chronological order of how phytohormones inside the seed act in accordance with the temperature and light signals from outside to degenerate the seed testa for the thriving seed’s germination has also been discussed.

Supplemental Blue Light Frequencies Improve Ripening and Nutritional Qualities of Tomato Fruits

Tomatoes (Solanum lycopersicum L. Micro-Tom) were grown in a plastic greenhouse. When plants anthesis, the 100 μmol m^-2 s^-1 blue light-emitting diode (LED) light (430 ± 10 nm) was supplemented from 6:00 to 18:00. There were 5 treatments, which contained different blue light frequencies with the same intensity: S6 (30 min blue light and 30 min pause), S8 (30 min blue light and 15 min pause), S10 (30 min blue and 8 min pause), S12 (continuous blue light for 12 h), and control (CK) (natural light, without any supplemental light). Agronomic traits and nutritional qualities of tomato fruits were measured at 30, 34, 38, 42, and 46 days after anthesis (DAA), respectively. Different frequencies of supplemental blue light could accelerate flowering of tomato plants and promote fruit ripening about 3-4 days early via promoting ethylene evolution of fruits, which significantly facilitated the processes of color change and maturity in tomato fruits. The contents of lycopene, total phenolic compounds, total flavonoids, vitamin C, and soluble sugar, as well as the overall antioxidant activity of tomato fruits were significantly enhanced by all the supplemental blue light treatments. In all, different frequencies of supplemental blue light prominently reinforced the antioxidant levels and nutritional qualities of tomato fruits, especially lycopene content, and S10 was more optimal for tomato fruits production in a plastic greenhouse.

Genomic Regions, Molecular Markers, and Flanking Genes of Metribuzin Tolerance in Wheat (Triticum aestivum L.)

Understanding the genetics of metribuzin (a group C herbicide) tolerance in wheat is vital in developing tolerant cultivars to improve wheat productivity in dryland farming systems. This study investigated metribuzin tolerance in wheat by conducting a Genome-wide Association Studies (GWAS) with a panel of 150 wheat genotypes of diverse genetic backgrounds and genotyped them with the wheat 90 K SNP genotyping assay. The phenotyping was conducted in a temperature-controlled glasshouse at the University of Western Australia (UWA). Genotypes were sprayed with a metribuzin dose of 400 grams of active ingredient (g. a.i.) ha^-1 as pre-emergent in a specialized spraying cabinet and transferred to the glasshouse where the tolerance level of the genotypes was assessed by measuring the relative reduction in chlorophyll content of the leaves. The decrease in chlorophyll content of the treated plants compared to the control was regarded as the phytotoxic effects of metribuzin. GWAS analysis following a mixed linear model revealed 19 genomic regions with significant marker-trait associations (MTAs), including ten on chromosome 6A, three on chromosome 2B, and one on chromosomes 3A, 5B, 6B 6D, 7A, and 7B, respectively. Sequences of the significant markers were blasted against the wheat genome, IWGSC RefSeq V1.0, and candidate genes having annotations related to herbicide tolerance in wheat, especially in pathways reported to be involved in metribuzin tolerance, such as cytochrome P450 pathways and ATP Binding Cassette (ABC) superfamilies, were identified in these genomic regions. These included TraesCS6A01G028800, TraesCS6A02G353700, TraesCS6A01G326200, TraesCS7A02G331000, and TraesCS2B01G465200. These genomic regions were validated on 30 top tolerant and 30 most susceptible genotypes using the five closest SSR makers to the flanked SNPs. Sufficient polymorphism was detected on two markers (wms193 and barc1036) that were found to differentiate between the susceptible and tolerant alleles and a t-test analysis of the phenotypic data shows a significant (value of p < 0.001) difference suggesting that these markers can be used for marker-assisted selection (MAS) in metribuzin studies and wheat breeding programs.

Understorey light quality affects leaf pigments and leaf phenology in different plant functional types

Forest understorey plants receive most sunlight in springtime before canopy closure, and in autumn following leaf-fall. We hypothesised that plant species must adjust their phenological and photoprotective strategies in response to large changes in the spectral composition of the sunlight they receive. Here, we identified how plant species growing in northern deciduous and evergreen forest understoreys differ in their response to blue light and ultraviolet (UV) radiation according to their functional strategy. We installed filters in a forest understorey in southern Finland, to create the following treatments attenuating: UV radiation below 350 nm, all UV radiation (< 400 nm), all blue light and UV radiation (< 500 nm), and a transparent control. In eight species, representing different functional strategies, we assessed leaf optical properties, phenology, and epidermal flavonoid contents over two years. Blue light accelerated leaf senescence in all species measured in the understorey, apart from Quercus robur seedlings, whereas UV radiation only accelerated leaf senescence in Acer platanoides seedlings. More light-demanding species accumulated flavonols in response to seasonal changes in light quality compared to shade-tolerant and wintergreen species and were particularly responsive to blue light. Reduction of blue and UV radiation under shade reveals an important role for microclimatic effects on autumn phenology and leaf photoprotection. An extension of canopy cover under climate change, and its associated suppression of understorey blue light and UV radiation, may delay leaf senescence for understorey species with an autumn niche.

AtCRY2 Negatively Regulates the Functions of AtANN2 and AtANN3 in Drought Tolerance by Affecting Their Subcellular Localization and Transmembrane Ca2+ Flow

Annexins are a multifunctional class of calcium-binding proteins in plants, and their physiological functions and regulation in response to drought stress remain to be elucidated. Here, we found that AtANN2 and AtANN3 conferred to drought tolerance under short-day and long-day conditions, respectively. Under their functional photoperiod, AtANN2 and AtANN3 gene expression was enhanced in the mannitol-treated roots, and their encoded proteins were rapidly targeted to the plasma membrane, and mediated significant Ca²⁺ flows across the plasma membrane. Cryptochromes as photoreceptors can not only sense the photoperiod and regulate ion channels on the plasma membrane to influence ion flow but also induce downstream physiological responses. AtCRY2 repressed the functions of AtANN2 and AtANN3 by affecting their plasma membrane localization and inhibited AtANN2- and AtANN3-dependent transmembrane Ca²⁺ flow in response to drought stress. Taken together, these results uncover a mechanism linking Annexins-AtCRY2 to transmembrane Ca²⁺ flow and resulting in enhanced drought tolerance in Arabidopsis.

A Review of Strawberry Photobiology and Fruit Flavonoids in Controlled Environments

Rapid technology development in controlled environment (CE) plant production has been applied to a large variety of plants. In recent years, strawberries have become a popular fruit for CE production because of their high economic and nutritional values. With the widespread use of light-emitting diode (LED) technology in the produce industry, growers can manipulate strawberry growth and development by providing specific light spectra. Manipulating light intensity and spectral composition can modify strawberry secondary metabolism and highly impact fruit quality and antioxidant properties. While the impact of visible light on secondary metabolite profiles for other greenhouse crops is well documented, more insight into the impact of different light spectra, from UV radiation to the visible light spectrum, on strawberry plants is required. This will allow growers to maximize yield and rapidly adapt to consumer preferences. In this review, a compilation of studies investigating the effect of light properties on strawberry fruit flavonoids is provided, and a comparative analysis of how light spectra influences strawberry's photobiology and secondary metabolism is presented. The effects of pre-harvest and post-harvest light treatments with UV radiation and visible light are considered. Future studies and implications for LED lighting configurations in strawberry fruit production for researchers and growers are discussed.

Cryptochrome 1 is modulated by blue light in human keratinocytes and exerts positive impact on human hair growth

Photoactivation of cryptochrome-family proteins by blue light is a well-established reaction regulating physiology of plants, fungi, bacteria, insects and birds, while impact of blue light on cryptochrome synthesis and/or activity in human non-visual cells remains unknown. Here, we show that 453 nm blue light induces cryptochrome 1 (CRY1) accumulation in human keratinocytes and the hair follicle. CRY1 is prominently expressed in the human anagen hair follicle, including epithelial stem cells. Specific silencing of CRY1 promotes catagen, while stimulation of CRY1 by KL001 prolongs anagen ex vivo by altering the expression of genes involved in apoptosis and proliferation. Together, our study identifies a role for CRY1 in sustaining human hair growth. Previously, we demonstrated positive effects of 453 nm blue light on hair growth ex vivo. Taken all together, our study suggests that CRY1 might mediate blue light-dependent positive effects on hair growth.

The International Symposium on Plant Photobiology 2019: a bright and colourful experience

Light is a key resource for plants as it fuels photosynthesis. It also provides essential information about their habitat. Thus, light tracking is of great importance to plants throughout their life cycle. To gain information about their light environment, plants possess light receptors that cover the perception of the complete light spectrum, including light invisible to the human eye (far-red and ultra-violet light). The information sensed by these photoreceptors is utilized for optimal growth during day-night cycles and in sub-optimal light conditions, such as shaded areas and high-light sun flecks. Plant photobiology research focuses on the perception of light by plants, their developmental adaptations to a changing light environment and the mechanistic and genetic basis of these adaptations. The International Symposium on Plant Photobiology (ISPP) is a biannual meeting where the world's leaders, as well as upcoming talents in the field, gather to share their latest results and discuss future directions. The past edition was held between June 3 and 8 of 2019 in the beautiful PRBB research park building on the seafront of the city of Barcelona (Spain). The ISPP2019 was organized by a gender-balanced committee formed by two junior (Lot Gommers and Jordi Moreno-Romero) and two senior researchers (Jamie F. Martínez-Garcia and Elena Monte).