12-h Dark Research Articles

Identification and management of a novel Danshen leaf anthracnose caused by Colletotrichum karstii in Salvia miltiorrhiza Bunge in China

Danshen (Salvia miltiorrhiza Bunge), a member of the genus Salvia within the Lamiaceae family, holds significant economic and medicinal value. Regrettably, the emergence of a novel leaf anthracnose in 2020 has significantly impacted its cultivation, leading to decreased yield and compromised quality. This newly identified pathogen was meticulously isolated from affected leaves, employing meticulous single conidia isolation techniques. Subsequent confirmation of pathogenicity was achieved through strict adherence of Koch’s postulates. To ensure precise identification, morphological characteristics were supplemented with tandem sequence analysis targeting the rDNA internal transcribed spacer (ITS), β-tubulin (TUB), and histone (His3) regions. Combining molecular biology techniques with morphological observation and Koch’s postulates, the pathogen was conclusively identified as Colletotrichum karstii. Further investigations focused on understanding the environmental factors influencing the mycelial growth and sporulation of the pathogen. The optimum temperature for the growth of C.karstii is 25°C, the suitable light conditions are 12h light/12h dark or 24h dark, and the suitable pH is 5 to 9. Utilizing BIOLOG phenotypic analysis technique, the metabolic utilization of carbon and nitrogen sources by the pathogen was assessed across different temperatures (20°C, 25°C, and 30°C). Results indicated the highest utilization rates at 25°C, particularly for arbutin and L-tryptophan. Lastly, the efficacy of 15 chemical fungicides and six botanical fungiticide against C. karstii was evaluated in vitro, revealing fluazinam as the most potent inhibitor against mycelial growth with EC50 of 0.0725 mg/mL for mycelium and 0.0378 mg/mL for spore germination, respectively. The 1 % osthole emulsion in water was found to have the strongest inhibitory effect on the growth of mycelium, with an EC50 value of 4.8984 µg/mL. Spore germination was most strongly inhibited by the 80 % ethylicin EC, which had an EC50 value of 0.5541 µg/mL. This study represents the first documentation of C. karstii as a causative agent of anthrax in Danshen, underscoring the significance of these findings for agricultural management and disease control strategies.

Removal of nutrients from synthetic wastewater by different Brazilian chlorophyte strains in batch bioreactors under various light regimes.

With the increase in pollution and improper waste disposal, aquatic ecosystems are experiencing escalating degradation leading to various detrimental effects, including eutrophication and adverse impacts on the health of the population reliant on these water resources. Consequently, microalgae have demonstrated efficacy in nutrient removal, minimal environmental disruption, and superior cost-effectiveness in comparison to traditional treatment methods. Thus, this study aimed to investigate wastewater treatment in an aerobic batch system, using two strains of non-axenic mixotrophic chlorophytes, Chlorella sp. and Desmodesmus sp., across distinct light regimes: continuous light exposure for 24h, a photoperiod of 12h light and 12h darkness, and complete absence of light for 24h. The Desmodesmus sp. strain exhibited superior efficiency in the proposed biological treatment, yielding more favorable nutrient removal results across all conditions, except for total nitrogen removal under the 24-h continuous light condition in which Chlorella sp. removed 0.199 ± 0.02% by biomass. In other parameters, Desmodesmus sp., remediated by biomass 0.408 ± 0.013% of inorganic phosphorus in 24h light, 0.372 ± 0.011% of COD and 0.416 ± 0.004% of carbohydrate in 24h dark. While Chlorella sp. removed 0.221 ± 0.01% of inorganic phosphorus in 24h light, 0.164 ± 0.02% of COD in 24h light and 0.214 ± 0.002% of carbohydrates in 24h dark. Nevertheless, both strains displayed potential as viable alternatives for wastewater biological treatment, indicating that nutrient removal is achievable across all tested light conditions, albeit with variations in efficiency depending on the specific nutrient type.

Revealing the adaptation mechanism of different color morphs of sea cucumber Apostichopus japonicus to light intensities from the perspective of metabolomics

Global warming has multi-dimensional and complex impacts on the Earth's system, among which changes in light intensities cannot be overlooked. Sea cucumbers are a marine biological resource with significant economic and ecological value. Their presence and activity help maintain the balance and stability of marine ecosystems. The variation in light intensities have important ecological effects on sea cucumbers. Light intensities can alter the synthesis and degradation of metabolic substances within the bodies of Apostichopus japonicus by changing their body color. Their changes affect the production of microorganisms in the environment, thereby achieving the goal of bioremediation. This study investigated metabolic variations in green, purple, and white sea cucumber Apostichopus japonicus under different light conditions (0 lx and 910 lx) with a 12-h light and 12-h dark photoperiod. The findings indicated that the sea cucumbers displayed more diverse metabolic alterations under 910 lx illumination compared to 0 lx. Specifically, these color morphs primarily responded to changes in light intensities through “tryptophan metabolism” and “biosynthesis of steroid hormones”. Additionally, high light intensities environment exacerbated the consumption of fatty acids by sea cucumbers. Different color morphs of sea cucumbers have differences in key metabolites in response to changes in light intensities. Green and white sea cucumbers primarily adapt to environment through phospholipids, while purple sea cucumbers mainly utilize fatty acids. These results enhance our comprehension of how sea cucumbers adapt ecologically to varying light intensities, and they offer valuable insights for systematically uncovering the regulatory processes that marine animals employ in response to environmental changes.

Light sensitivity of the circadian system in the social Highveld mole-rat Cryptomys hottentotus pretoriae.

Highveld mole-rats (Cryptomys hottentotus pretoriae) are social rodents that inhabit networks of subterranean tunnels. In their natural environment, they are rarely exposed to light, and consequently their visual systems have regressed over evolutionary time. However, in the laboratory they display nocturnal activity, suggesting that they are sensitive to changes in ambient illumination. We examined the robustness of the Highveld mole-rat circadian system by assessing its locomotor activity under decreasing light intensities. Mole-rats were subjected to seven consecutive light cycles commencing with a control cycle (overhead fluorescent lighting at 150lx), followed by decreasing LED lighting (500, 300, 100, 10 and 1lx) on a 12h light:12h dark (L:D) photoperiod and finally a constant darkness (DD) cycle. Mole-rats displayed nocturnal activity under the whole range of experimental lighting conditions, with a distinct spike in activity at the end of the dark phase in all cycles. The mole-rats were least active during the control cycle under fluorescent light, locomotor activity increased steadily with decreasing LED light intensities, and the highest activity was exhibited when the light was completely removed. In constant darkness, mole-rats displayed free-running rhythms with periods (τ) ranging from 23.77 to 24.38 h, but was overall very close to 24 h at 24.07 h. Our findings confirm that the Highveld mole-rat has a higher threshold for light compared with aboveground dwelling rodents, which is congruent with previous neurological findings, and has implications for behavioural rhythms.

Enhancement of In Vitro Seed Germination, Growth, and Root Development in Two Sideritis Species through GA3 Application and Diverse LED Light Conditions

The Sideritis genus includes over 150 species primarily found in the Mediterranean basin, including the S. clandestina subsp. pelopponesiaca from the Peloponnese and S. scardica from North and Central Greece. In vitro seed germination has proven effective for conserving and amplifying the genetic diversity of endangered species such as Sideritis. This study aimed to optimize in vitro germination and seedling growth of S. scardica and S. clandestina subsp. pelopponesiaca under different lighting conditions at 22 °C, including white fluorescent lamps (WFL-BG-40) and LEDs (LED-BGYOR-40, LED-BR-40, LED-BR-80, LED-BR-120) all under a 16-h light/8-h dark photoperiod (WFL: white fluorescent light, B:blue, G:green, Y:yellow, O:orange, R:red, 40–80–120 μmol m−2 s−1), along with a 24-h dark treatment. The results indicated that LED-BR-80 combined with 250 mg L−1 GA3 in the MS medium promoted best germination (40%, day 55) and shoot proliferation in S. clandestina subsp. pelopponesiaca. Conversely, 5-year-old cold stratified S. scardica seeds showed higher germination rates (80%) and robust seedling growth under LED-BGYOR-40 with 250 mg L−1 GA3, particularly thriving in LED-BR-120 for increased shoot height and root number. This is the first report of the efficacy of LED technology in optimizing in vitro conditions for Sideritis species, crucial for their conservation and sustainable commercial cultivation.

The impacts of sex and the 5xFAD model of Alzheimer's disease on the sleep and spatial learning responses to feeding time.

The relationships between the feeding rhythm, sleep and cognition in Alzheimer's disease (AD) are incompletely understood, but meal time could provide an easy-to-implement method of curtailing disease-associated disruptions in sleep and cognition. Furthermore, known sex differences in AD incidence could relate to sex differences in circadian rhythm/sleep/cognition interactions. The 5xFAD transgenic mouse model of AD and non-transgenic wild-type controls were studied. Both female and male mice were used. Food access was restricted each day to either the 12-h light phase (light-fed groups) or the 12-h dark phase (dark-fed groups). Sleep (electroencephalographic/electromyographic) recording and cognitive behavior measures were collected. The 5xFAD genotype reduces NREM and REM as well as the number of sleep spindles. In wild-type mice, light-fed groups had disrupted vigilance state amounts, characteristics, and rhythms relative to dark-fed groups. These feeding time differences were reduced in 5xFAD mice. Sex modulates these effects. 5xFAD mice display poorer spatial memory that, in female mice, is curtailed by dark phase feeding. Similarly, female 5xFAD mice have decreased anxiety-associated behavior. These emotional and cognitive measures are correlated with REM amount. Our study demonstrates that the timing of feeding can alter many aspects of wake, NREM and REM. Unexpectedly, 5xFAD mice are less sensitive to these feeding time effects. 5xFAD mice demonstrate deficits in cognition which are correlated with REM, suggesting that this circadian-timed aspect of sleep may link feeding time and cognition. Sex plays an important role in regulating the impact of feeding time on sleep and cognition in both wild-type and 5xFAD mice, with females showing a greater cognitive response to feeding time than males.

EFFECTS OF MELATONIN ADMINISTRATION ON MORTALITY AND ECONOMICS OF BROILER CHICKENS EXPOSED TO CONTINUOUS LIGHTING AND HEAT STRESS

This study was conducted to determine the impact of continuous lighting and heat stress on the mortality and economics of broiler chickens, administered with melatonin during the hot-dry season. Broiler chicks were assigned randomly into three groups, comprising 100 chicks each. Group I was raised under natural photoperiod of 12-h light and 12-h darkness, without melatonin supplementation. Group II was kept under 24-h continuous lighting, without melatonin administration. Group III was raised under 24-h continuous lighting, with melatonin supplementation at 0.5 mg/kg per os, via drinking water. Melatonin was administered once daily for 42 consecutive days at 17:00 h. The weekly mean temperature-humidity index recorded inside the poultry house was lowest at week 4 of the study, with the value of 48.60 ± 0.08 "C; but highest at week 1, with the value of 53.48 ± 0.97 °C (P<0.0001). Groups I, II and III had overall mortality of 5, 6 and 1 %, respectively. The highest profit value of 667:55 was obtained in group III broiler chickens, administered with melatonin. In conclusion, oral administration of melatonin may enhance adaptation to heat stress and productivity of broiler chickens in the tropical zones of the world.

Effects of light on reproduction of the Mediterranean medicinal leech, Hirudo verbana Carena, 1820: do circadian rhythm disruptions positively affect reproductive performance of leeches?

ABSTRACT This study aimed to assess the impact of light on the reproductive performance of leeches for the first time using the Mediterranean medicinal leech Hirudo verbana Carena, 1820, which is important in medicinal leech aquaculture. Gravid leeches were subjected to three different light conditions: 24-h Light, 24-h Dark, and Daylight (14-h light and 10-h dark) for 11 weeks. Gravidity ended at the 8th week for the Dark (5.33 ± 0.38 weeks) and Daylight (5.41 ± 0.29 weeks) groups, whereas it persisted for 11 weeks in the Light group (6.75 ± 0.51 weeks) (p = 0.031). In comparison to the Daylight group (cocoons: 40, offspring: 538), the Light (cocoons: 50, offspring: 723) and Dark (cocoons: 45, offspring: 576) groups achieved a greater yield of cocoons (p = 0.312) and offspring (p = 0.323). We invite discussion on the notion that the enhanced reproductive capacity of leeches in full light and full dark conditions, as opposed to daylight, may be attributed to the disturbance of their circadian rhythms.

Research Note: Effects of different light-emitting diode lights during egg incubation on hatching performance and embryo development in White King pigeons

The light provide during incubation can influence hatching characteristics (hatching time, hatchability, etc.) and embryo development in chickens, geese, and turkeys. However, relevant studies on this factor in pigeons are lacking. This study investigated the effects of in ovo photostimulation during embryogenesis on hatching performance, squab quality, and embryo development in pigeons. 400 eggs from paired- bred pigeons were randomly distributed into 4 incubation lighting treatments, with 2 replicates per treatment. The treatments included dark as a control (NL), 12-h light, and 12-h dark photoperiods of white light (WL), red light (RL), and green light (GL) (100 lx at egg level) during the first 15 d of incubation. A total of 1,600 eggs in 4 batches from White King pigeons were used. The results showed that hatching time of the WL group was significantly shorter than that of the dark light group (P < 0.05). The hatchability of fertile eggs in the WL group was significantly higher (P < 0.05), whereas the hatchability of fertile eggs in the RL group was significantly lower (P < 0.05) than that of in the control group. Light stimulation had no effect on time to 90% hatching or average hatching time (P > 0.05). In addition, the hatch window was not extended by light stimulation (P > 0.05). The group incubated under GL showed an increase in embryo weight and relative leg muscle on embryonic d 14 and the hatching day compared to the dark incubation (P < 0.05). Green light stimulated the heart and liver development during the early and middle stages of embryogenesis. It was concluded that white light stimulation during embryogenesis accelerated the hatching process, whereas monochromatic green light had a positive effect on embryo development. Our findings provide important guidance for developing light protocols for pigeon egg incubation.

Lengthened circadian rhythms in mice with self-controlled ambient light intensity

Laboratory animals are typically maintained under 12-h light and 12-h dark (12:12 LD) conditions with a daytime light intensity of ~ 200 lx. In this study, we designed an apparatus that allowed mice to self-select the room light intensity by nose poking. We measured the behavioral rhythms of the mice under this self-controlled light regimen. The mice quickly learned the relationship between their nose pokes and the resulting changes in the light intensity. Under these conditions, the mice exhibited free-running circadian behavior with a period of 24.5 ± 0.4 h. This circadian period was ~ 1 h longer than that of the same strain of mice when they were kept in constant darkness (DD) after 12:12 LD entrainment, and the lengthened period lasted for at least 30 days. The rhythm of the light intensity controlled by the mice also exhibited a similar period, but the phase of the illuminance rhythm preceded the phase of the locomotor activity rhythm. Mice that did not have access to the light controller were also entrained to the illuminance cycle produced by the mice that did have access to the light controller, but with a slightly delayed phase. The rhythm was likely controlled by the canonical circadian clock because mice with tau mutations in the circadian clock gene CSNK1E exhibited short periods of circadian rhythm under the same conditions. These results indicate that the free-running period of mice in the wild may differ from what they exhibit if they are attuned by forced light cycles in laboratories because mice in their natural habitats can self-control their exposure to ambient light, similar to our experimental conditions.

Effect of pH and Light Intensity on the Growth of Dunaliella Salina

&#x0D; &#x0D; &#x0D; Dunaliella salina is a unicellular halophilic green alga dominantly found in salt lakes, and high saline ponds in slatterns all over the world. A rigid cell wall is absent in D. salina while the cells are covered by mucous materials that are enclosed by a thin elastic plasma membrane. This species has both environmental and economic validity as they are capable of producing β–carotene during photosynthesis. Synthesis of β–carotene in D. salina is a function of environmental factors, and thus, the present study was designed to study the effect of pH of the medium and light intensity on the growth of D. salina. The Algae sample was collected from a crystalizing pond of Hambantota Saltern, Sri Lanka, and a monoculture was maintained under suitable laboratory conditions. The seawater sample with pH 7.66 was used to prepare a series of pH using sodium carbonate anhydrous. These cultures were exposed to a series of pH (7.66, 8.0, 8.50, and 9.0) at two light intensities (885 lux and 200 lux). All experimental setups were maintained at 25oC with the photoperiod of 12h light and 12h dark. Four replicates of each pH medium were arranged into a 4×4 setup of flasks for each light intensity and the experiment was conducted for four weeks. At the end of the fourth week, the pH level of all flasks ranged from 8.27 to 8.53 due to the self-adjustment of the pH level in the culture medium in parallel to algal growth. The maximum growth was reflected by the highest absorbance of 1.46 at 750 nm. Taken together, our findings revealed that the optimum pH range and light intensity for culturing D. salina is 8.27-8.53 and 885 lux respectively. This study recommends further research on culturing of D. salina for extracting the bioproduct of β -carotene at various light intensity levels.&#x0D; Keywords: Cell density, β –carotene, Light intensity, Self-adjusted&#x0D; &#x0D; &#x0D;

Influence of coloured lights on growth and enzyme production of beneficial endophytic fungi.

The influence of light regulation on fungal growth and enzyme production was tested on endophytic isolates of Fusarium proliferatum (CCH), Colletotrichum boninense (PL1, PL9, OL2), Colletotrichum gloeosporiodes (OL3) and Colletotrichum siamense (PL3). The isolates were treated with blue, red, green, and yellow light, while white fluorescent light (12h light/12h dark photoperiod) and 24h dark conditions were applied as control. Results revealed that coloured light treatments induced formation of circadian rings, while exposure to white light and dark conditions showed less pronounced circadian rings. Growth and sporulation of endophytes were not significantly influenced by light. By contrast, enzyme production was affected by coloured light treatments, notably with red (amylase), blue (cellulase) and yellow (cellulase, xylanase, L-asparaginase) light, resulting in lower enzyme levels for certain isolates. Under control conditions, enzyme production was relatively higher for amylase, cellulase, xylanase (for cultures incubated in the dark), and for L-asparaginase (for cultures incubated in white fluorescent light). Among the endophytic isolates, F. proliferatum (CCH) showed better response to coloured light treatment as higher sporulation and enzyme production was detected, although growth was significantly suppressed. On the contrary, C. gloeosporiodes (OL3) showed better growth but significantly lower enzyme production and sporulation when treated with the various coloured light. This study revealed that coloured light may have the potential to manipulate growth, sporulation and enzyme production in certain fungal species as strategies for fungal control or for harnessing of valuable enzymes.

High photoreactivation activities of Rad2 and Rad14 in recovering insecticidal Beauveria bassiana from solar UV damage

Anti-ultraviolet (UV) roles of Rad2 and Rad14 depend on nucleotide excision repair (NER) of UV-induced DNA lesions in budding yeast but remain unexplored yet in filamentous fungi. Here, nucleus-specific Rad2 and Rad14 orthologs are shown to recover Beauveria bassiana, a main source of wide-spectrum mycoinsecticides, from solar UV damage through photorepair-depending photoreactivation. As a photorepair index, photoreactivation (germination) rates of lethal UVB dose-irradiated conidia via a 3- or 5-h light plus 9- or 7-h dark incubation at 25 °C were drastically reduced in the Δrad2 and Δrad14 mutants versus a wild-type strain. As an NER index, nighttime-mimicking 12-h dark reactivation rates of low UVB dose-impaired conidia decreased sharply compared to the corresponding photoreactivation rates in the presence or absence of either ortholog, indicating that its extant NER activity was limited to recovering light UVB damage in the field. The high photoreactivation activity of either Rad2 or Rad14 was derived from its tight link to a large protein complex formed by photolyase regulators and other anti-UV proteins through multiple protein-protein interactions revealed by yeast two-hybrid assays. Therefore, Rad2 and Rad14 recover B. bassiana from solar UV damage through photoreactiovation in vivo that depends primarily on photorepair, although they contribute little to the fungal lifecycle-related phenotypes. These findings unveil a novel scenario distinguished from the NER-depending anti-UV roles of Rad2 and Rad14 in the model yeast and broaden a biological basis crucial for rational application of fungal insecticides to improve pest control efficacy via feasible recovery of solar UV damage.

Rad6, a ubiquitin conjugator required for insect-pathogenic lifestyle, UV damage repair, and genomic expression of Beauveria bassiana

The E2 ubiquitin conjugator Rad6 is required for DNA damage bypass in budding yeast but remain functionally unknown in filamentous fungi. Here, we report pleiotropic effect of Rad6 ortholog in Beauveria bassiana, a wide-spectrum fungal insecticide. Global ubiquitination signal was greatly attenuated in the absence of rad6. The blocked ubiquitination led to severe growth defect, blocked asexual development, and abolished infectivity/insect pathogenicity, which correlated with compromised conidial quality (including viability, hydrophobicity, adherence to insect cuticle, and thermotolerance) and blocked secretion of cuticle-degrading enzymes including Pr1 family proteases. Importantly, Rad6 played much greater role in photoreactivation of UVB-impaired conidia by a 3- or 5-h light plus 9- or 7-h dark incubation than in dark reactivation of those impaired conidia by a 12-h dark incubation. The high activity of Rad6 in photoreactivation in vivo was derived from its link to a protein complex cored by the photolyase regulators WC1 and WC2 via the strong interactions of Rad6 with the E3 partner Rad18 and Rad18 with WC2 revealed in yeast two-hybrid assays. Transcriptomic analysis resulted in identification of 2700 differentially regulated genes involved in various function categories and metabolism pathways, indicating a regulatory role of Rad6-mediated ubiquitination in gene expression networks and genomic stability. Conclusively, Rad6 is required for asexual and insect-pathogenic lifecycles, solar UV damage repair, and genomic expression of B. bassiana. The primary dependence of its strong anti-UV role on photoreactivation in vivo unveils a scenario distinct from the core role of its yeast ortholog in DNA damage bypass.

Rad2, Rad14 and Rad26 recover Metarhizium robertsii from solar UV damage through photoreactivation in vivo

Rad2, Rad14 and Rad26 recover ultraviolet (UV) damage by nucleotide excision repair (NER) in budding yeast but their functions in filamentous fungi have not been elucidated. Here, we report mechanistically different anti-UV effects of nucleus-specific Rad2, Rad14 and Rad26 orthologs in Metarhizium robertsii, an insect-pathogenic fungus. The null mutants of rad2, rad14 and rad26 showed a decrease of ∼90% in conidial resistance to UVB irradiation. When conidia were impaired at a UVB dose of 0.15 J/cm2, they were photoreactivated (germinated) by only 6–13% through a 5-h light plus 19-h dark incubation, whereas 100%, 80% and 70% of the wild-type conidia were photoreactivated at 0.15, 0.3 and 0.4 J/cm2, respectively. The dose-dependent photoreactivation rates were far greater than the corresponding 24-h dark reactivation rates and were largely enhanced by the overexpression (OE) of rad2, rad14 or rad26 in the wild-type strain. The OE strains exhibited markedly greater activities in photoreactivation of conidia inactivated at 0.5–0.7 J/cm2 than did the wild-type strain. Confirmed interactions of Rad2, Rad14 and Rad26 with photolyase regulators and/or Rad1 or Rad10 suggest that each of these proteins could have evolved into a component of the photolyase regulator-cored protein complex to mediate photoreactivation. The interactions inhibited in the null mutants resulted in transcriptional abolishment or repression of those factors involved in the complex. In conclusion, the anti-UV effects of Rad2, Rad14 and Rad26 depend primarily on DNA photorepair-dependent photoreactivation in M. robertsii and mechanistically differ from those of yeast orthologs depending on NER.

In vitro asymbiotic propagation of the vulnerable slipper orchid Cypripedium cordigerum D. Don

This paper presents an attempt to establish a protocol for the conservation of Cypripedium cordigerum D. Don a vulnerable species of orchid using in vitro symbiotic seed germination. The suitability of four orchids seed germination media [Terrestrial orchid medium (BM), modified terrestrial orchid seed germination medium (BM-1), Malmgren modified terrestrial orchid medium (MM), Knudson C medium (KC)] was tested using different photoperiods i.e. 24-h dark or 12-h light per day. The seed capsules were harvested at two different stages of development in order to determine the effect of capsule maturity on seed germination. The maximum percentage germination of seed from intact capsules in the dark was 65.00 ± 0.12% on the BM-1 medium. Release of brownish exudates was stopped by the addition of activated charcoal to the cultures. Seedlings developed in 26.17 ± 0.17 weeks. The current study is the first to report the ex-situ conservation of C. cordigerum.

MiR-277 regulates the phase of circadian activity-rest rhythm in Drosophila melanogaster.

Circadian clocks temporally organize behaviour and physiology of organisms with a rhythmicity of about 24h. In Drosophila, the circadian clock is composed of mainly four clock genes: period (per), timeless (tim), Clock (Clk) and cycle (cyc) which constitutes the transcription-translation feedback loop. The circadian clock is further regulated via post-transcriptional and post-translational mechanisms among which microRNAs (miRNAs) are well known post-transcriptional regulatory molecules. Here, we identified and characterized the role of miRNA-277 (miR-277) expressed in the clock neurons in regulating the circadian rhythm. Downregulation of miR-277 in the pacemaker neurons expressing circadian neuropeptide, pigment dispersing factor (PDF) advanced the phase of the morning activity peak under 12h light: 12h dark cycles (LD) at lower light intensities and these flies exhibited less robust rhythms compared to the controls under constant darkness. In addition, downregulation of miR-277 in the PDF expressing neurons abolished the Clk gene transcript oscillation under LD. Our study points to the potential role of miR-277 in fine tuning the Clk expression and in maintaining the phase of the circadian rhythm in Drosophila.

First Report of Bacterial Leaf Blight caused by Enterobacter asburiae on Sorghum in Jiangsu Province, China.

Sorghum (Sorghum bicolor [L.] Moench) is a major cereal crop in China, with a planting area of more than 674666 ha in 2021. In August 2022, bacterial leaf blight symptoms were observed on sorghum plants grown in a field in Huai'an (119.30437 ºE, 33.999644 ºN), in Jiangsu Province (Fig. 1). To determine the causal agent, four symptomatic leaves from different plants were surface sterilized with 75% (v/v) ethanol for 1 min and washed three times with ddH2O. The surface-sterilized plant tissues were cut into small pieces (4 × 4 mm in size) and cultured on Nutrient Agar (NA) plates at 28ºC for 24 h. To obtain pure cultures, these colonies were transferred to fresh NA plates by using the conventional streak plate method. The purified bacterial cells were rod-shaped, from 1.14 to 1.66 μm long, and from 0.61 to 0.86 μm wide (number of observations = 31) (Fig. 2). Three isolates were used for further characterization. The Gram stain test indicated that the three isolates were Gram negative. 16S rRNA (27F/1492R primers) and gyrB (UP1/Up2r) genes were amplified and sequenced (Marchesi et al. 1998; Yamamoto and Harayama 1995). The obtained 16S rRNA (0R143361-0R143363) and gyrB sequences (0R146993-0R146995) were submitted to GenBank. The 16S rRNA sequences of the three isolated strains showed over 98% identity (1447/1462, 1438/1462 and 1443/1460 bp) to the E. asburiae reference strains ENIPBJ CG1, CAV1043 and 1808 013 (CP014993.1, CP011591.1 and AP019632.1, respectively). Similarly, the gyrB sequences of the three strains showed 98% identity (1103/1129, 1105/1129 and 1108/1129 bp) to the same E. asburiae reference strains. Four-week-old sorghum plants were used in the pathogenicity tests. A phylogenetic tree was constructed with reference strains (Hoffmann et al., 2005). The healthy leaves were inoculated with bacterial suspensions of the three bacterial isolates (OD600 = 0.6~1.0) using the leaf cutting method (Kauffman et al. 1973). For the control group, sterilized ddH2O was used. Each isolate was inoculated in three healthy plants. Inoculated plants were incubated at 28ºC and 75% humidity with alternating 12-h light and 12-h dark cycles with a photon flux density of 200 mmol/m2/s. After 10 days, bacterial leaf blight symptoms were observed in all the inoculated leaves. The inoculated leaves showed severe browning near the inoculation site (1-2 cm), and advanced yellowing from 2 to 7 cm from the inoculation site, while no symptoms were found in control group. The pathogen was recovered from the infected leaves, and its identity was confirmed by 16S rRNA/gyrB sequencing and morphological analysis, fulfilling Koch's postulates (Fig 2). To our knowledge, this is the first report of E. asburiae causing bacterial leaf blight on sorghum worldwide. This species is a well-known pathogen of humans that can cause nosocomial infections (Markovska et al. 2019; Zhu et al. 2017). Recently, E. asburiae was identified as the causal agent of bacterial blight on rice and tuber rot on radish (Wang et al. 2023; Yu et al. 2021). The emergence E. asburiae as a plant pathogen may be produced by the numerous resistant strains reported during recent years. Pantoea ananatis has been reported as a common companion pathogen of E. asburiae (Xue et al. 2021). This report will help to better understand the host promiscuity of E. asburiae and reveals a new pathogen that affects sorghum production in China. This study also serves as a basis for future studies to develop management strategies and cultivation for the disease to prevent sorghum yield loss. As far as we know, no control method for the management of this new plant pathogen was reported to date, which highlights the potential hazard of this discovery. Reference Hoffmann, H., et al. 2005. Syst. Appl. Microbiol. 28:196. Kauffman, H. E., et al. 1973. Plant Dis. Rep. 57:537. Marchesi, J. R., et al. 1998. Appl. Environ. Microbiol. 64:795. Markovska, R., et al. 2019. Infect. Dis. 51:627. Wang, R., et al. 2023. Plant Dis. in press. https://doi.org/10.1094/PDIS-11-22-2650-PDN Xue, Y., et al. 2021. Plant Dis. 105:2078. Yamamoto, S., et al. 1995. Appl. Environ. Microbiol. 61:1104. Yu, L., et al. 2021. Plant Dis. 106:310. Zhu, B., et al. 2017. J. Glob. Antimicrob. Resist. 8:104.

Differential responses to artificial photoperiods of the rising and falling phases of human melatonin rhythm are consistent with a dual oscillator hypothesis.

Circadian rhythms and sleep-wake cycles were measured in volunteers staying singly in temporal isolation unit where they were exposed to artificial short and long light-dark (LD) cycles for 7 days. The long day consisted of 16-h light and 8-h dark (LD 16:8) and the short day consisted of 8-h light and 16-h dark (LD 8:16). During the light period, bright light of approximately 5,000 lux was given from the ceiling and during the dark period there was no illumination. Sleep was monitored by bed sensors, wrist actiwatch, and polysomnography (PSG) on the first and last nights of the schedule. Sleep length was significantly longer under LD 8:16 than under LD 16:8 and the sleep quality estimated by PSG was worse under LD 8:16 than under LD 16:8, which were comparable to natural seasonality in sleep. The circadian rhythm in plasma melatonin was measured in dim light (10 lux) before and after the LD exposures. The nocturnal melatonin secretion (NMS) was significantly longer after LD 8:16 than after LD 16:8 due to differential phase shifts of the rising and falling phases of NMS. After LD 8:16, the falling phase was much advanced than the rising phase, whereas after LD 16:8 the rising phase was much delayed than the falling phase, resulting in the NMS compression. These results indicate that the light sensitivity in terms of phase shifting is different in the two circadian phases, supporting a dual oscillator hypothesis with different phase-response curves for light in the human circadian system.NEW & NOTEWORTHY The present study demonstrated differential light responsiveness of the rising and falling phases of nocturnal melatonin secretion in human subjects exposed to artificial long (LD 16:8) and short days (LD 8:16) and suggested the involvement of different oscillators under these phases. The findings well mimicked the seasonality of the circadian rhythms in nature and consisted with the evening/morning dual oscillator hypothesis proposed originally for nocturnal rodents, providing a new concept for the human circadian system.

Seasonal light hours modulate peripheral clocks and energy metabolism in mice

Except for latitudes close to the equator, seasonal variation in light hours can change dramatically between summer and winter. Yet investigations into the interplay between energy metabolism and circadian rhythms typically use a 12h light:12h dark photoperiod corresponding to the light duration at the equator. We hypothesized that altering the seasonal photoperiod affects both the rhythmicity of peripheral tissue clocks and energy homeostasis. Mice were housed at photoperiods representing either light hours in summer, winter, or the equinox. Mice housed at a winter photoperiod exhibited an increase in the amplitude of rhythmic lipid metabolism and a modest reduction in fat mass and liver triglyceride content. Comparing melatonin-proficient and -deficient mice, the effect of seasonal light on energy metabolism was largely driven by differences in the rhythmicity of food intake and not melatonin. Together, these data indicate that seasonal light impacts energy metabolism by modulating the timing of eating.