Light-dark Periods Research Articles

Is the diel cycle of routine metabolic rate in mummichog (Fundulus heteroclitus) affected by near-infrared lighting used for visualizing behavior of fishes at night?

The metabolic rate of a freely moving fish (routine metabolic rate) is tightly coupled with volitional movement (spontaneous activity), both of which commonly show strong daily cycles linked to the species-specific diel activity pattern. Mummichog (Fundulus heteroclitus), an important estuarine fish in the north western Atlantic Ocean, are historically reported as diurnal (i.e., more active during daylight). Our recent laboratory studies on a Bay of Fundy population, however, showed a free-running (i.e., similarly active daytime and night-time) or even nocturnal (i.e., more active at night-time) diel activity pattern. In the laboratory, near-infrared (NIR) illumination is commonly used with a NIR-sensitive camera to visualize fish activity across the light-dark periods of the day. Because NIR light is close to the visible light spectrum and certain fishes show sensitivity to NIR, the use of NIR with mummichog possibly could disturb the animals and obscure the identification of their true diel activity pattern. We aimed to determine if NIR illumination (940 nm wavelength) influences the diel activity pattern of mummichog. We used measurements of routine metabolic rate (oxygen consumption rate, MO2) as a proxy for activity, as evaluating the effect of NIR requires treatments where NIR lights are off, which precludes visualization and direct assessment of fish activity at night-time. We measured routine MO2 of mummichogs over 6 days, exposed to either NIR off-on-off (2 days for each off or on period) or the opposite sequence of NIR on-off-on (to control for time-dependent effects). NIR lights did not influence the diel cycle of routine MO2, and activity by proxy, in mummichog. Thus, NIR illumination is a suitable method to visualize mummichog during light-dark diel cycles. Routine MO2, and presumably activity, was similar or higher during night-time periods compared to daytime periods, confirming a free-running or nocturnal activity pattern for at least certain populations of mummichog.

RNA-Seq Analysis Demystify the Pathways of UV-A Supplementation in Different Photoperiods Integrated with Blue and Red Light on Morphology and Phytochemical Profile of Kale

As an indispensable element in the morphology and phytochemical profile of plants, UV-A has proved to help promote the growth and quality of kale. In this study, UV-A supplementation in different photoperiods (light period supplemental UVA = LS, dark period supplemental UVA = DS, and light-dark period supplemental UVA = LDS) contributed to yielding greater biomass production (fresh weight, dry weight, and plant moisture content), thus improving morphology (plant height, stem diameter, etc.) and promoting higher phytochemicals content (flavonoids, vitamin c, etc.), especially glucosinolates. To fathom its mechanisms, this study, using RNA-seq, verified that UV-A supplementation treatments signally generated related DEGs of plant hormone signal pathway, circadian rhythm plant pathway, glucosinolate pathway, etc. Moreover, 2047 DEGs were obtained in WGCNA, illustrating the correlations between genes, treatments, and pathways. Additionally, DS remarkedly up-regulated related DEGs of the key pathways and ultimately contributed to promoting the stem diameter, plant height, etc., thus increasing the pigment, biomass, vitamin c, etc., enhancing the antioxidant capacity, and most importantly, boosting the accumulations of glucosinolates in kale. In short, this study displayed new insights into UV-A supplementation affected the pathways related to the morphology and phytochemical profile of kale in plant factories.

INTERACTION OF CO2 AND LIGHT AVAILABILITY ON PHOTOPHYSIOLOGY OF TROPICAL COCCOLITOPHORIDS (EMILIANIA HUXLEYI, GEPHYROCAPSA OCEANICA, AND OCHOSPHAERA SP.)

The study to examine the calcification rate, adaptation, and the biotic response of three tropical coccolithophorids (Emiliania huxleyi, Gephyrocapsa oceanica, and Ochosphaera sp) to changes in CO2 concentration. Three selected calcifying coccolitophorids were grown at batch culture with CO2 system at two levels of CO2 (385 and 1000 ppm) and two light dark periods. The parameters measured and calculation including growth rate, particulate organic carbon content, particulate inorganic carbon content, chlorophyll a, cell size, photosynthetic, organic, inorganic carbon production, photosynthesis, and calcification rate. The results showed that there was a different response to carbonate chemistry changes and dark and light periods in any of the analyzed parameters. The growth rate of three selected calcifying microalgae tested was decreasing significantly at high concentrations of CO2 (1000 ppm) treatment on 14:10 hour light: dark periods. However, there was no significant difference between the two CO2 concentrations where they were illuminated by 24 hours light in growth rate. The increasing CO2 concentration and light-dark periods were species-specific responses to photosynthesis and calcification rate for three selected calcifying microalgae.

First report of Coniella koreana causing leaf blight on Loropetalum chinense var. rubrum (Chinese Fringe Flower) in Sichuan, China.

Loropetalum chinense var. rubrum (Chinese Fringe Flower) is widely distributed in the middle and lower reaches of the Yangtze River, as well as northern India. It is a popular landscape plant for its red evergreen foliage and its showy red flowers in the spring. In July 2020, This leaf blight was discovered in Chengdu city (30°42＇41＂N, 103°51＇58＂E). In June 2021, the disease incidence rate at two places in Wenjiang District of Chengdu was 76% and 64%, respectively. The symptoms began to appear from May to June, worsened from July to August, and then disappeared gradually in November. Initially, brown-edged irregular necrotic patches appeared at the leaf margins. Progressively, the patches increased in number, expanded to leaf middle, and turned grayish-white. The scattered black fruiting bodies (conidia) were appeared at patches under humid conditions. Eventually, the leaves tended to dry up and fall off. Infected tissues from five samples and collected were cut into small pieces 2×2 mm, surface sterilized for 30 s in 3% sodium hypochlorite, 60 s in 75% ethanol, rinsed three times in sterile water, placed onto potato dextrose agar (PDA), and incubated at 25℃ in the dark. A total of eight isolates were collected, five isolates exhibited similar culture characteristics while two were Nigrospora sp. and one was a Fusarium sp.. The five similar isolates produced sparse, grayish-withe mycelia with a flat elevation and curled margin. Abundant globose and yellow pycnidia were formed on the PDA surface and arranged in irregular concentric zones. Conidia were 18.20 to 22.36 × 2.64 to 3.05 μm (average 20.36 × 2.82 μm, n=50) in size, fusiform, sickle-shaped, aseptate. DNA was extracted from the representative strain (HMcj B03), and the internal transcribed spacer (ITS) region, the large subunit of the nuclear ribosomal DNA (LSU), translation elongation factor 1-alpha (tef1-α), and the DNA-directed RNA polymerase II second largest subunit (rpb2), were amplified by polymerase chain reaction and sequenced with primers ITS1/ITS4 (White et al. 1990), LR0R/LR7 (Rehner and Samuels 1994; Vilaglys and Hester 1990), 728F/986R (Carbome and Kohn 1999), and 5F2/7cR (Alvarez et al. 2016), respectively. The sequences were deposited in GenBank, viz. OL468959, OL469170, OL489770, and OL855833, respectively. BLAST analysis showed >98.7% identity with several reference sequences of Coniella koreana strain CBS 143.97 and Coniella quercicola strain CBS 904.69, deposited in GenBank. A conidial suspension (1 × 107 conidia/mL) having 0.05% Tween 80 buffer was used for foliar inoculation of 6-year-old Loropetalum chinense var. rubrum plants for pathogenicity test. Ten leaves of each plant (10 pots in total) were inoculated with spore suspensions (20 μL onto the wounded sites). An equal number of control leaves were sprayed with 0.05% Tween 80 buffer to serve as a control. The experiment was repeated three times, and all plants were incubated in a growth chamber (a 12h light and 12h dark period, 25°C, RH > 80%). Twenty days later, all the inoculated leaves showed similar symptoms as the original diseased plants, however, the controls remained asymptomatic. The C. koreana was re-isolated from the infected leaves. To our knowledge, this is the first report of L. chinense var. rubrum caused by C. koreana in China. The discovery of this new disease will provide useful information for developing effective control strategies, and prove beneficial in reducing economic losses in floral product.

The impact of different seed dormancy release treatments on seed germination of juniper (Juniperus procera)

BackgroundJuniper (Juniperus procera) is a common forest tree species in Saudi Arabia. The Juniper forests face frequent episodes of wildfires; therefore, reforestation is necessary to maintain optimum forest cover in the country. However, Juniper seeds are extremely dormant and germinating them is a tough task. This study assessed the potential of different seed dormancy release treatments in improving the seed germination of Juniper. MethodsEight different seed dormancy-release treatments, i.e., boiling seeds for 2, 4 and 6 min, chemical scarification with concentrated sulfuric acid for 2, 4 and 6 min, stratification at 4 °C for 8 weeks and mechanical scarification with sandpaper were tested. A control treatment without any seed dormancy-release treatment was included in the experiment for comparison. The experiments were conducted under three different light:dark regimes, i.e., continuous dark, continuous light and alternating light and dark period of 12 h. Furthermore, the impact of four different potassium nitrate (KNO3) levels, i.e., 0, 2.5, 5 and 10 Mm was tested on seedling traits. Data related to seed germination was recorded at 4, 6, 8 and 10 weeks after initiation of the experiment. ResultsThe seeds were highly dormant and those in control treatment failed to germinate after 4 weeks. The highest seed germination was recorded for mechanical scarification under all light dark periods (37, 33 and 41 % for continuous dark, continuous light and alternating light and dark, respectively). Overall, the improvement in seed germination by mechanical scarification was 47, 25 and 34 % under continuous dark, continuous light and alternating light and dark, respectively compared to control treatment after 10 weeks. Seedling traits were significantly improved by the application of 5 Mm KNO3 compared to control treatment and higher concentration proved toxic. ConclusionIt is concluded that mechanical scarification can be used to releases seed dormancy of Juniper seeds. Furthermore, 5 Mm KNO3 could be utilized to improve the early seedling growth.

IoT-based LED Lighting System with Variable Pulsing Frequency and Dark Periods for Sunflower Microgreens

For growing microgreens, it is necessary to understand the effect of the lighting conditions to reach a balance between energy consumption and optimal production of a particular crop. The objective of this study is to develop an IoT-based LED lighting system with adjustable lighting parameters that will maximize the production of sunflower microgreens. The system implemented a controlled environment monitored by sensors and regulated through a single-board computer and microcontroller module. A central composite design and response surface methodology were also used to distinguish the optimum combination of light pulse frequency and dark period. Results proved that shorter dark periods and lower frequencies produced large leaf areas and longer stem lengths. However, increasing the dark period to a maximum of 8 seconds can still result in sizeable crop production by adjusting the pulse frequency between 300 Hz to 600 Hz. It is then possible for growers to decrease power consumption and produce quality yield by controlling the dark period and pulse frequency subjected to the crops

Effect of Photoblastism on Rice Morphogenesis and Seedling Development

The effect of continuous light and complete dark period on seed germination to first leaf emergence was examined in BRRIdhan71 and BRRIdhan81 in controlled environment at 22 ± 2 ᵒC and 82± 2 % of relative humidity, with or without supplemental LED white light. In the dark, BRRIdhan71 had a germination rate of 97 percent and BRRIdhan81 had a germination rate of 57 percent. Germination was 92 percent in BRRIdhan81 and 77 percent in BRRIdhan71 under photoblastic conditions (Light). The dark and light treatments had a noticeable impact on the percentage of seeds that germinated. Coleoptile was longer in dark than light in BRRIdhan71. In both rice varieties, the light and dark treatments had little effect on the first leaf length, although the first leaf breadth increased noticeably in BRRIdhan81. The growth condition had an impact on root length, seedling fresh weight, and dry weight. Germination percent, coleoptile length, prophyll length, first leaf length, and root length all decreased in BRRIdhan71, whereas germination percent, first leaf length, first leaf breadth, seedling freash, and dry weight all increased significantly in BRRIdhan81.The findings imply that BRRIdhan71 and BRRIdhan81, in particular, responded to photoblastic treatment and predominantly possess photoblastic biocomponents in seed, which affect germination and subsequent growth phases. Rice seed during germinate in the field will light stress if photoblastism is not considered during the development and release of rice varieties for different seasons, such as Aman and Boro, because light affects seeding photomorphogenesis differently in different growth environments.
 Environ. Sci. & Natural Resources, 13(1&2): 43-49, 2020

First Report of Coniella castaneicola Causing Leaf Blight on Blueberry (Vaccinium virgatum) in China.

Blueberry (Vaccinium virgatum), an economically important small fruit crop, is characterized by its highly nutritive compounds and high content and wide diversity of bioactive compounds (Miller et al. 2019). In September 2020, an unknown leaf blight disease was observed on Rabbiteye blueberry at the Agricultural Science and Technology Park of Jiangxi Agricultural University in Nanchang, China (28°45'51"N, 115°50'52"E). Disease surveys were conducted at that time, the results showed that disease incidence was 90% from a sampled population of 100 plants in the field, and this disease had not been found at other cultivation fields in Nanchang. Leaf blight disease on blueberry caused the leaves to shrivel and curl, or even fall off, which hindered floral bud development and subsequent yield potential. Symptoms of the disease initially appeared as irregular brown spots (1 to 7 mm in diameter) on the leaves, subsequently coalescing to form large irregular taupe lesions (4 to 15 mm in diameter) which became curly. As the disease progressed, irregular grey-brown and blighted lesion ran throughout the leaf lamina from leaf tip to entire leaf sheath and finally caused dieback and even shoot blight. To identify the causal agent, 15 small pieces (5 mm2) of symptomatic leaves were excised from the junction of diseased and healthy tissue, surface-sterilized in 75% ethanol solution for 30 sec and 0.1% mercuric chloride solution for 2 min, rinsed three times with sterile distilled water, and then incubated on potato dextrose agar (PDA) at 28°C for 5-7 days in darkness. Five fungal isolates showing similar morphological characteristics were obtained as pure cultures by single-spore isolation. All fungal colonies on PDA were white with sparse creeping hyphae. Pycnidia were spherical, light brown, and produced numerous conidia. Conidia were 10.60 to 20.12 × 1.98 to 3.11 µm (average 15.27 × 2.52 µm, n = 100), fusiform, sickle-shaped, light brown, without septa. Based on morphological characteristics, the fungal isolates were suspected to be Coniella castaneicola (Cui 2015). To further confirm the identity of this putative pathogen, two representative isolates LGZ2 and LGZ3 were selected for molecular identification. The internal transcribed spacer region (ITS) and large subunit (LSU) were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004) and LROR/LR7 (Castlebury and Rossman 2002). The sequences of ITS region (GenBank accession nos. MW672530 and MW856809) showed 100% identity with accessions numbers KF564280 (576/576 bp), MW208111 (544/544 bp), MW208112 (544/544 bp) of C. castaneicola. LSU gene sequences (GenBank accession nos. MW856810 to 11) was 99.85% (1324/1326 bp, 1329/1331 bp) identical to the sequences of C. castaneicola (KY473971, KR232683 to 84). Pathogenicity was tested on three blueberry varieties ('Rabbiteye', 'Double Peak' and 'Pink Lemonade'), and four healthy young leaves of a potted blueberry of each variety with and without injury were inoculated with 20 μl suspension of prepared spores (106 conidia/mL) derived from 7-day-old cultures of LGZ2, respectively. In addition, four leaves of each variety with and without injury were sprayed with sterile distilled water as a control, respectively. The experiment was repeated three times, and all plants were incubated in a growth chamber (a 12h light and 12h dark period, 25°C, RH greater than 80%). After 4 days, all the inoculated leaves started showing disease symptoms (large irregular grey-brown lesions) as those observed in the field and there was no difference in severity recorded between the blueberry varieties, whereas the control leaves showed no symptoms. The fungus was reisolated from the inoculated leaves and confirmed as C. castaneicola by morphological and molecular identification, fulfilling Koch's postulates. To our knowledge, this is the first report of C. castaneicola causing leaf blight on blueberries in China. The discovery of this new disease and the identification of the pathogen will provide useful information for developing effective control strategies, reducing economic losses in blueberry production, and promoting the development of the blueberry industry.

The Circadian Clock Is Sustained in the Thyroid Gland of VIP Receptor 2 Deficient Mice.

VIP/VPAC2-receptor signaling is crucial for functioning of the circadian clock in the suprachiasmatic nucleus (SCN) since the lack results in disrupted synchrony between SCN cells and altered locomotor activity, body temperature, hormone secretion and heart rhythm. Endocrine glands, including the thyroid, show daily oscillations in clock gene expression and hormone secretion, and SCN projections target neurosecretory hypothalamic thyroid-stimulating hormone (TSH)-releasing hormone cells. The aim of the study was to gain knowledge of mechanisms important for regulation of the thyroid clock by evaluating the impact of VIP/VPAC2-receptor signaling. Quantifications of mRNAs of three clock genes (Per1, Per2 and Bmal1) in thyroids of wild type (WT) and VPAC2-receptor deficient mice were done by qPCR. Tissues were taken every 4th h during 24-h 12:12 light-dark (LD) and constant darkness (DD) periods, both genders were used. PER1 immunoreactivity was visualized on sections of both WT and VPAC2 lacking mice during a LD cycle. Finally, TSH and the thyroid hormone T4 levels were measured in the sera by commercial ELISAs. During LD, rhythmic expression of all three mRNA was found in both the WT and knockout animals. In VPAC2-receptor knockout animals, the amplitudes were approximately halved compared to the ones in the WT mice. In the WT, Per1 mRNA peaked around “sunset”, Per2 mRNA followed with approximately 2 h, while Bmal1 mRNA was in antiphase with Per1. In the VPAC2 knockout mice, the phases of the mRNAs were advanced approximately 5 h compared to the WT. During DD, the phases of all the mRNAs were identical to the ones found during LD in both groups of mice. PER1 immunoreactivity was delayed compared to its mRNA and peaked during the night in follicular cells of both the thyroid and parathyroid glands in the WT animals. In WT animals, TSH was high around the transition to darkness compared to light-on, while T4 did not change during the 24 h cycle. In conclusion, sustained and identical rhythms (phases and amplitudes) of three clock genes were found in VPAC2 deficient mice during LD and DD suggesting high degree of independence of the thyroid clock from the master SCN clock.

Investigation of complement system activation and regulation during Indian Antarctic expedition

Antarctica is one of the most effective sites to measure the impact of human isolation, sleep deprivation, light-dark period and harsh environmental conditions. In the present study we address several aspects of the activation and regulation of the complement system. Alterations in the body systems mainly related to immunology, physiology and psychology, during expeditions to the Antarctica, leads to various complexities. In the present study the research findings are based on two group members from 34th Indian Scientific Expedition to the Antarctic. The first group-included members from “summer” expedition, while the second group-included members subjected to the Antarctic environment for the “winter” expedition. Blood samples were collected from both the groups and evaluated for various activation and regulatory complement protein. Serum levels of C3, C4 & C5a were analysed. Anaphylatoxin C3a was up regulated significantly in both the teams. However, C5a, another anaphylatoxin was also increased in both teams though not significantly during winter expedition. Complement regulatory proteins C1- Inhibitor, Factor D, Factor H were unregulated significantly during summer and winter exposures. However, Factor D levels increased significantly only in the month of April (W2) of summer exposure. Thus, this indicates that harsh Antarctic conditions could be detrimental factor for activation of complement system in both the teams. However, the effect of activated complement system during the expedition was regulated in positive manner and could not be correlated with clinical manifestations due to the multiple stressors and small population size during Antarctic expedition.

Complementary phase responses via functional differentiation of dual negative feedback loops.

Multiple feedback loops are often found in gene regulations for various cellular functions. In mammalian circadian clocks, oscillations of Period1 (Per1) and Period2 (Per2) expression are caused by interacting negative feedback loops (NFLs) whose protein products with similar molecular functions repress each other. However, Per1 expression peaks earlier than Per2 in the pacemaker tissue, raising the question of whether the peak time difference reflects their different dynamical functions. Here, we address this question by analyzing phase responses of the circadian clock caused by light-induced transcription of both Per1 and Per2 mRNAs. Through mathematical analyses of dual NFLs, we show that phase advance is mainly driven by light inputs to the repressor with an earlier expression peak as Per1, whereas phase delay is driven by the other repressor with a later peak as Per2. Due to the complementary contributions to phase responses, the ratio of light-induced transcription rates between Per1 and Per2 determines the magnitude and direction of phase shifts at each time of day. Specifically, stronger Per1 light induction than Per2 results in a phase response curve (PRC) with a larger phase advance zone than delay zone as observed in rats and hamsters, whereas stronger Per2 induction causes a larger delay zone as observed in mice. Furthermore, the ratio of light-induced transcription rates required for entrainment is determined by the relation between the circadian and light-dark periods. Namely, if the autonomous period of a circadian clock is longer than the light-dark period, a larger light-induced transcription rate of Per1 than Per2 is required for entrainment, and vice versa. In short, the time difference between Per1 and Per2 expression peaks can differentiate their dynamical functions. The resultant complementary contributions to phase responses can determine entrainability of the circadian clock to the light-dark cycle.

First Report of Alternaria tenuissimain Causing Leaf Spot of Celery (Apium graveolens) in China.

Celery (Apium graveolens) is one of the most widely grown vegetables in the world. A survey in Anding District of Gansu Province in 2019 showed that the incidence of celery leaf spot was 25%-45%. The disease mainly occurs in late June and July. The leaf spot is conducive to the onset at high temperature and humidity environment. The initial symptoms were many small light brown, irregular-shaped on the leaves. The lesions gradually enlarged in the later stage of the disease, and multiple lesions coalesced to form large irregular brown spots, eventually the whole leaves died. A 3~4mm leaf tissue was cut from the junction of the diseased leaf and the healthy area, the leaf tisse was surface-sterilized in 1.5% NaClO for 1 min and washed with sterile water. Then, it was incubated on potato dextrose agar (PDA) and obtained the pure culture (Q1). After 5 days of cultivation at 25°C, the fungal colonies were olivaceous to dark olive with white margins and abundant aerial mycelia. The conidia were obclavate or ellipsoid, pale brown, with 3~4 longitudinal septa and 2~7 transverse septa, and measured 20.0 to 50.0 × 3.5 to 14.0μm (n=50). Conidiophores were septate, arising singly, and measured 3.5 to 40.0 × 2.5 to 4.5 μm (n=50). Based on morphological characteristics, the fungus was preliminarily identified as A.tenuissima (Simmons 2007). To further confirm the identification, the internal transcribed spacer region (ITS), translation elongation factor 1-α gene (TEF), RNA polymerase II second largest subunit (RPB2), major allergen Alt a 1 gene (Alt a 1), endopolygalacturonase gene (endoPG), anonymous gene region (OPA10-2) and glyceraldehyde 3-phos-phatedehydrogenase (GAPDH) were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004), EF1-728F/EF1-986R (Carbone et al. 1999), RPB2-5F2/RPB2-5R (Sung et al. 2007), Alt-for/Alt-rev (Hong et al. 2005), EPG-specific/EPG-3b (Peever et al. 2004), OPA10-2R/OPA10-2L (Peever et al. 2004) and Gpd1/Gpd2 (Berbee et al. 1999) (GenBank accession no.MN046364, MW016001, MW016002, MW016003, MW016004, MW016005, MW016006). DNA sequences of TEF, RPB2, endoPG, OPA10-2 and GAPDH were 100% identical to those of A. tenuissima (MN256108, MK605866, KP789503, JQ859829 and MK683802), but ITS and Alt a 1 were 100% similarity with A. tenuissima (MN615420, JQ282277) and A. alternate (MT626589, KP123847). The ITS and Alt a 1 sequence did not distinguish A. tenuissima from the A. alternate complex. Maximum likelihood phylogenetic analyses were performed for the combined data set with TEF, RPB2, and endoPG using MEGA6 under the Tamura-Nei model (Kumar et al. 2016). The isolate Q1 clustered with type strain A. tenuissima CBS 918.96. The 20 celery plants of 4-7 leaf age were used test the pathogenicity of Q1, the ten plants were sprayed with 20ml of spore suspension (1×105 spores/ml), the control was sprayed with 20mL sterile water, which were placed in a growth chamber (25℃, a 14h light and 10h dark period, RH > 80%). Eight days after inoculation, 40% of the leaves formed lesions, which were consistent with the field observation，the control group was asymptomatic. The pathogen was reisolated from infected leaves to fulfill Koch's postulates. To our knowledge, this is the first report of A. tenuissima causing leaf spot on celery in China.

Altering light–dark cycle at pre-harvest stage regulated growth, nutritional quality, and photosynthetic pigment content of hydroponic lettuce

Lettuce exposed to red (R) and blue (B) LEDs (4R:1B, 200 μmol·m−2·s−1) were cultivated hydroponically in an environmentally controlled plant factory to examine the effects of light–dark cycle (LDC) conversion at pre-harvest stage on the growth, phytochemical, and photosynthetic pigment accumulation of lettuce. Lettuce plants of four groups were firstly cultivated with the same LDC of 16/8 h (light/dark) for fourteen days. Six days before harvest, the LDC of three groups were altered to 8/4 h (T12), 24/12 h (T36), and 32/16 h (T48), respectively. The last group had invariable photoperiod and was concerned as control (CK, 16/8 h). The results showed that T12 and T36 significantly improved while T48 reduced leaf area and shoot fresh and dry weight of lettuce compared with the CK. The plants treated with altered LDC had higher phytochemicals (soluble sugar, soluble protein, and ascorbate) and photosynthetic pigments (chlorophyll and carotenoids) contents than the CK, but the starch and nitrate contents of the CK were higher. These results suggested that the yield and nutritional quality of lettuce can be increased by changing the LDC properly in the later growth stage. But if the light–dark period was too long, it would have negative effects on the growth of lettuce. In addition, shorten the LDC at pre-harvest stage promoted better production yield and nutritional quality based on the same electricity consumption.

Behavioral change and transcriptomics reveal the effects of 2, 2′, 4, 4′-tetrabromodiphenyl ether exposure on neurodevelopmental toxicity to zebrafish (Danio rerio) in early life stage

Polybrominated diphenyl ethers (PBDEs) are a class of widely used flame retardants, and their residue in the environment may threaten the ecosystem and human health. The neurodevelopmental toxic effects of PBDEs have been verified in previous studies, but the mechanisms are still unclear. Behavioral analysis and transcriptomics were performed in this study to assess the neurodevelopmental toxic effects of PBDEs on zebrafish embryos and larvae, and the potential mechanisms. The embryos were collected after fertilization and exposed to control (0.05% DMSO), 10, 50, 100 (ug/L) 2, 2′, 4, 4′-tetrabromodiphenyl ether (BDE-47) for 7 days. The locomotion parameters of larvae were recorded and analyzed by a behavioral analysis system (EthoVision XT, Noldus). Enrichment of functions and signaling pathways of differentially expressed genes (DEGs) were analyzed by GO and DAVID database. The comparison with the control group showed adverse developments such as low hatching rate, high mortality rate, alterative heart rate, and abnormal spontaneous tail coiling frequency of embryos (24hpf). For the zebrafish larvae, behavioral analyses results suggested decreased activities and movements of the treatment in the light-dark period at 120, 144 and 168hpf, especially the 50 and 100μg/L groups. The affected functions included steroid hormone regulation, neuro regulation, circadian regulation, cardioblast differentiation, immune-related regulation. The enrichment of KEGG pathways were Hedgehog signaling (Shh), Toll-like receptor signaling, FoxO signaling, and Steroid biosynthesis pathway. Hedgehog signaling pathway was further verified via RT-qPCR for its major role in the development of neurogenesis. The mRNA levels of Shh pathway indicated the inhibition of Shh signal in our study since shha, patched1, gli1 and gli2 genes were significantly down-regulated. In summary, PBDEs might influence the neurodevelopment of zebrafish in the early life stage by multiple toxic signaling pathways alteration.

Differential carbohydrate dynamics in Arabidopsis wild-type and ntrc mutant after trehalose feeding

The trehalose sugar plays pivotal roles in plants. In Arabidopsis, trehalose supplied to the medium leads to starch accumulation through redox activation of the ADP-glucose pyrophosphorylase (AGPase) by the NADPH-dependent thioredoxin reductase C (NTRC). To gain further insight on the regulation of carbohydrate metabolism by trehalose and NTRC, Arabidopsis wild-type (wt) and ntrc plants were raised in the MS medium supplemented with or without 100-mM sucrose or trehalose and alterations in sugar and starch contents as well as the activities and expressions of some carbohydrate metabolizing enzymes were investigated. The ntrc plants displayed lower growth rate compared to wt by sugar feeding. Under trehalose treatment, the total soluble, reducing and non-reducing sugars of wt and ntrc plants decreased between end of the day and end of the night, but starch in the ntrc plants remained unaltered during the aforementioned period. The obtained data showed that trehalase activity and gene expression display diurnal rhythms. Meanwhile, under darkness, trehalase gene expression required functional NTRC. Trehalose feeding induced NTRC expression during the day, but suppressed it during the night. Moreover, AGPase expression found to be jointly regulated by carbon nutrition and the light–dark period in both wt and mutant plants. The current data also revealed that AMY3 (α-amylase 3) gene expression depends on the presence of functional NTRC in plants. It seems that cross-talk between trehalose and NTRC regulates diurnal carbohydrate metabolism in plants.

Blue and red light upregulate α-expansin 1 (EXPA1) in transgenic Brassica rapa and its overexpression promotes leaf and root growth in Arabidopsis

Light quality and the cell-growth-related proteins called expansins (EXPs) are two crucial factors in plant growth and development. However, molecular insights into the light responses of EXPs and the influences of light-dependent EXP expression changes on plant growth and development remain scarce. A preliminary analysis using a cDNA microarray revealed that red, blue, violet, and far-red light emitting diode (LED) light exposure and dark periods differentially regulate the expression of 27 Brassica rapa EXPs (BrEXPs). The results indicated that photosynthetically significant red and blue light induce the expression of BrEXPA1, and these results were further confirmed using a semi-qRT-PCR assay. The identification of several light-responsive cis-regulatory elements in the BrEXP promoter sequences suggested that light signals were perceived through these promoter motifs to regulate the gene expression that eventually controls growth and development. To substantiate our hypothesis that the light-dependent regulation of EXPs modulates growth and development, we developed transgenic reporter lines of B. rapa expressing GUS under the BrEXPA1 promoter. A histochemical analysis showed that BrEXPA1-promoter-driven GUS activity was prominent in the leaves, radicles, lateral roots, and flowers of plants grown under monochromatic red or blue light. The biological functions of BrEXPA1 were further tested by overexpressing sense (OE-S) and antisense BrEXPA1 (OE-AS) transcripts in Arabidopsis. The OE-S lines displayed long radicles, wide leaves, and additional rosette leaves compared to the controls, whereas the OE-AS lines exhibited early bolting. Collectively, our results demonstrated the relationship between light and BrEXPs and also the light-dependent role of BrEXPA1 in growth regulation.

Is light dark periodicity an obligate requirement for flower opening in Oenothera glazioviana Micheli: a nocturnal flower

Flower opening depends on light–dark periods in diurnal plants, while this role of light in nocturnal plants is elusive. To elucidate this, an experiment with sprays of Oenothera glazioviana was carried out. Sprays were divided into 3 sets. First set of sprays was kept in the laboratory with alternate light and dark period (Control), second set of sprays was kept under continuous light and third set of sprays was kept under continuous darkness held in distilled water or sucrose (0.025 M) along with CoCl2 (0.01 mM). Flowers opened normally in all treatments but the sprays kept under continuous darkness showed maximum flower longevity, floral diameter, % blooms, soluble proteins and sugar fractions as compared to control which instead maintained an increased membrane stability index besides a decrease in lipid peroxidation. The sprays under continuous light showed increased α-amino acid and total phenolic content. The addition of sucrose augmented flower opening even under continuous light or darkness suggesting that light is not an obligatory requirement for flower opening in Oenothera glazioviana.

Daily oscillations in expression and responsiveness of Toll-like receptors in splenic immune cells

Circadian rhythms refer to biologic processes that oscillate with an approximate 24-h period. These rhythms direct nearly all aspects of animal behavior and physiology. The aim of our study was to determine if Toll-like receptor (TLR) expression and responsiveness exhibit time-of-day dependent differences. Therefore, we isolated an adherent splenocyte population, which consisted primarily of B cells, dendritic cells, and macrophages, over the course of a 24-h light-dark period and measured daily changes in Tlr1-8 mRNA levels and cytokine expression after cells were challenged at Zeitgeber time (ZT) 1 or ZT13 with a TLR ligand. In addition, we assessed TLR3 protein levels in adherent splenocytes over the 24-h light-dark period and challenged mice at ZT1 or ZT13 with poly(I:C), the TLR3 ligand. Our study revealed that in this adherent cell population, all Tlrs exhibited rhythmic expression except Tlr2 and Tlr5, and all TLRs, except TLR8, demonstrated daily variations in responsiveness after challenge with their respective ligand. We also revealed that TLR3 protein levels fluctuate over the daily light-dark cycle in adherent splenocytes and mice exhibit a time-of-day dependent immune response when challenged with poly(I:C). Finally, we demonstrated that mRNA levels of Tlr2 and Tlr6 display rhythmic expression in splenic macrophages. Taken together, these findings could have important implications for TLR-directed therapeutics.

Field and laboratory experiments on the locomotor activity patterns in juvenile and adult individuals of the desert isopod Hemilepistus reaumurii

In recent years, many studies were interested in the activity behaviour in the field which represents the best way to study ecological aspects of locomotor activity behaviour. This has been facilitated by advances in methodological approaches to the recording of locomotor activity in the laboratory. Behavioural activity of adults and juveniles of Hemilepistus reaumurii collected from the arid region of Bchachma (Kairouan, Tunisia) was investigated by both field and laboratory studies during the beginning of summer (June). In their natural environment, results showed a bimodal distribution of activities occurring around dawn and dusk for both adults and juveniles. However, adults were more active in the early morning whereas the most important activity peak of juveniles occurred later in the afternoon. Under controlled environmental conditions, our results showed that adults and juveniles exploit differently the temporal niche. Furthermore, adults’ locomotor rhythm was more stable and better defined than juveniles. Activity patterns of adults recorded in the laboratory were found to be similar to that observed in nature. Indeed, adults have limited their activity to light-dark transition periods coinciding with the experimental dawn and dusk. However, juveniles were found to be more active around sunrise and during the middle of the experimental day.

Rewarding Effects of Operant Dry-Licking Behavior on Neuronal Firing in the Nucleus Accumbens Core.

Certain eating behaviors are characterized by a trend of elevated food consumption. However, neural mechanisms mediating the motivation for food consumption are not fully understood. Food impacts the brain-rewarding-system via both oral-sensory and post-ingestive information. Recent studies have reported an important role of visceral gut information in mediating dopamine (DA) release in the brain rewarding system. This is independent of oral sensation, suggesting a role of the gut-brain-DA-axis in feeding behavior. In this study, we investigated the effects of intra-gastric (IG) self-administration of glucose on neuronal firings in the nucleus accumbens (NA) of water-deprived rats. Rats were trained in an operant-licking paradigm. During training, when the light was on for 2 min (light-period), rats were required to lick a spout to acquire the water oral-intake learning, and either an IG self-infusion of 0.4 M glucose (GLU group) or water (H2O group). Rats rested in the dark-period (3 min) following the light-period. Four cycles of the operant-licking paradigm consisting of the light–dark periods were performed per day, for 4 consecutive days. In the test session, the same rats licked the same spout to acquire the IG self-administration of the corresponding solutions, without oral water ingestion (dry licking). Behavioral results indicated IG self-administration of glucose elicits more dry-licking behavior than that of water. Neurophysiological results indicated in the dark period, coefficient of variance (CV) measuring the inter-spike interval variability of putative medial spiny neurons (pMSNs) in the NA was reduced in the H2O group compared to the GLU group, while there was no significant difference in physical behaviors in the dark period between the two groups. Since previous studies reported that DA release increases CV of MSNs, the present results suggest that greater CV of pMSNs in the GLU group reflects greater DA release in the NA and elevated motivation in the GLU group, which might increase lickings in the test session in the GLU group compared to the H2O group.