Continuous Dark Conditions Research Articles

Transcriptional Modulation during Photomorphogenesis in Rice Seedlings.

Light is one of the most important factors regulating plant gene expression patterns, metabolism, physiology, growth, and development. To explore how light may induce or alter transcript splicing, we conducted RNA-Seq-based transcriptome analyses by comparing the samples harvested as etiolated seedlings grown under continuous dark conditions vs. the light-treated green seedlings. The study aims to reveal differentially regulated protein-coding genes and novel long noncoding RNAs (lncRNAs), their light-induced alternative splicing, and their association with biological pathways. We identified 14,766 differentially expressed genes, of which 4369 genes showed alternative splicing. We observed that genes mapped to the plastid-localized methyl-erythritol-phosphate (MEP) pathway were light-upregulated compared to the cytosolic mevalonate (MVA) pathway genes. Many of these genes also undergo splicing. These pathways provide crucial metabolite precursors for the biosynthesis of secondary metabolic compounds needed for chloroplast biogenesis, the establishment of a successful photosynthetic apparatus, and photomorphogenesis. In the chromosome-wide survey of the light-induced transcriptome, we observed intron retention as the most predominant splicing event. In addition, we identified 1709 novel lncRNA transcripts in our transcriptome data. This study provides insights on light-regulated gene expression and alternative splicing in rice.

Diurnal-Rhythmic Relationships between Physiological Parameters and Photosynthesis- and Antioxidant-Enzyme Genes Expression in the Raphidophyte Chattonella marina Complex.

Diurnal rhythms in physiological functions contribute to homeostasis in many organisms. Although relationships between molecular biology and diurnal rhythms have been well studied in model organisms like higher plants, those in harmful algal bloom species are poorly understood. Here we measured several physiological parameters and the expression patterns of photosynthesis-related and antioxidant-enzyme genes in the Chattonella marina complex to understand the biological meaning of diurnal rhythm. Under a light-dark cycle, Fv/Fm and expression of psbA, psbD, and 2-Cys prx showed significant increases in the light and decreases during the dark. These rhythms remained even under continuous dark conditions. DCMU suppressed the induction of psbA, psbD, and 2-Cys prx expression under both light regimes. Oxidative stress levels and H2O2 scavenging activities were relatively stable, and there was no significant correlation between H2O2 scavenging activities and antioxidant-enzyme gene expression. These results indicate that the Chattonella marina complex has developed mechanisms for efficient photosynthetic energy production in the light. Our results showed that this species has a diurnal rhythm and a biological clock. These phenomena are thought to contribute to the efficiency of physiological activities centered on photosynthesis and cell growth related to the diurnal vertical movement of this species.

Metagenomic analysis of microbial consortia native to the Amazon, Highlands, and Galapagos regions of Ecuador with potential for wastewater remediation.

Native microbial consortia have been proposed for biological wastewater treatment, but their diversity and function remain poorly understood. This study investigated three native microalgae-bacteria consortia collected from the Amazon, Highlands, and Galapagos regions of Ecuador to assess their metagenomes and wastewater remediation potential. The consortia were evaluated for 12 days under light (LC) and continuous dark conditions (CDC) to measure their capacity for nutrient and organic matter removal from synthetic wastewater (SWW). Overall, all three consortia demonstrated higher nutrient removal efficiencies under LC than CDC, with the Amazon and Galapagos consortia outperforming the Highlands consortium in nutrient removal capabilities. Despite differences in α- and β-diversity, microbial species diversity within and between consortia did not directly correlate with their nutrient removal capabilities. However, all three consortia were enriched with core taxonomic groups associated with wastewater remediation activities. Our analyses further revealed higher abundances for nutrient removing microorganisms in the Amazon and Galapagos consortia compared with the Highland consortium. Finally, this study also uncovered the contribution of novel microbial groups that enhance wastewater bioremediation processes. These groups have not previously been reported as part of the core microbial groups commonly found in wastewater communities, thereby highlighting the potential of investigating microbial consortia isolated from ecosystems of megadiverse countries like Ecuador.

Transmittance of PDMS film on the fluorescent performance and synergistic antifouling effect of SWLAP/PDMS composite coatings

The film-forming substances in waterborne silicone coatings play a crucial role in the properties of coatings. A novel waterborne fluorescent antifouling coating inspired by fluorescent coral was reported in this paper. A series of sky-blue waterproof long afterglow phosphor (SWLAP)/polydimethylsiloxane (PDMS) composite coatings were prepared with different properties of hydroxy‑terminated silicone oil emulsion (HT-SOE). SWLAP is irradiated by sunlight during the day and emits fluorescence at night to interfere with the normal physiological activities of marine organisms. The high transmittance of PDMS films formed by HT-SOE contributes to the high fluorescence intensity of coatings. The adhesion behavior of marine bacteria and Navicula sp. on the coatings was studied under simulated alternative day-night, continuous light, and constant dark conditions. The results showed that the bacterial adhesion rate (BAR) and diatom removal rate (DRR) under simulated alternative day-night conditions of coatings was significantly decreased and increased, respectively. C-S20/5011 had the best static and dynamic antifouling performance. The BAR was only 2.46 % after 24 h and DRR reached 39.9 % after 48 h. Under continuous light or dark conditions, the antifouling abilities of coatings mainly depend on their surface performance and mechanical properties. The fluorescence effect played an important role in the synergistic antifouling mechanism. This study provides a new idea for environmentally friendly antifouling coatings and becomes an important step in the development of green and long-acting marine antifouling coatings.

Settlement behavior and mechanism of Navicula sp. on WLAP/PDMS composite coating under simulative diurnal alternation, constant light and dark conditions

Marine biological fouling is a persistent issue facing the marine industries, which not only causes damage to the underwater facilities but also results in substantial financial losses. Diatoms are one of the most harmful polluters in the ocean. In this paper, novel antifouling coatings inspired by fluorescent coral were reported. Waterproof long afterglow phosphors (WLAP) were introduced into the cross-linked network of polydimethylsiloxane (PDMS). WLAP can absorb and store light energy during the day and emit weak fluorescence at night, which affects the normal physiological activities of diatoms. Through the synergistic mechanism of low surface energy and fluorescence antifouling, excellent antifouling performance is achieved throughout the day. The settlement behavior of Navicula sp. on WLAP/PDMS composite coatings was studied under simulative diurnal alternation, continuous light, and dark conditions. The results demonstrated that the adhesion of diatoms on WLAP/PDMS composite coatings decreased significantly under simulative diurnal alternation. The inhibition effect of the sky-blue composite coating was the most obvious. The attachment reduction rate (ARR) was 35.4% compared with the blank control coating, and the diatom removal rate (DRR) after washing was 42.3%. Constant light conditions also affect the normal physiological activities of diatoms, while the feeble light of coatings is covered. In continuous dark condition, the antifouling abilities of coatings mainly depend on their low surface energy. The composite waterborne coatings prepared in this research is non-toxic and eco-friendly and can recycle solar energy, which supply a new direction for enhancing the static antifouling ability of coatings and an environmentally friendly antifouling strategy, and becomes an important step for sustainable development.

Influence of Light Conditions on the Antibacterial Performance and Mechanism of Waterborne Fluorescent Coatings Based on Waterproof Long Afterglow Phosphors/PDMS Composites.

Marine microbial adhesion is the fundamental cause of large-scale biological fouling. Low surface energy coatings can prevent marine installations from biofouling; nevertheless, their static antifouling abilities are limited in the absence of shear forces produced by seawater. Novel waterborne antifouling coatings inspired by fluorescent coral were reported in this paper. Waterproof long afterglow phosphors (WLAP) were introduced into waterborne silicone elastomers by the physical blending method. The composite coatings store energy during the day, and the various colors of light emitted at night affect the regular physiological activities of marine bacteria. Due to the synergistic effect of fouling-release and fluorescence antifouling, the WLAP/polydimethylsiloxane (PDMS) composite coating showed excellent antifouling abilities. The antibacterial performance of coatings was tested under simulated day-night alternation, continuous light, and constant dark conditions, respectively. The results illustrated that the antibacterial performance of composite coatings under simulated day-night alternation conditions was significantly better than that under continuous light or darkness. The weak lights emitted by the coating can effectively inhibit the adhesion of bacteria. C-SB/PDMS showed the best antibacterial effect, with a bacterial adhesion rate (BAR) of only 3.7%. Constant strong light also affects the normal physiological behavior of bacteria, and the weak light of coatings was covered. The antibacterial ability of coatings primarily relied on their surface properties under continuous dark conditions. The fluorescent effect played a vital role in the synergetic antifouling mechanism. This study enhanced the static antifouling abilities of coatings and provided a new direction for environmentally friendly and long-acting marine antifouling coatings.

SerpinB1 is required for Rev-erbα-mediated protection against acute lung injury induced by lipopolysaccharide-in mice.

Acute lung injury (ALI) is a serious, life-threatening inflammation of the lungs that still lacks effective treatment. We previously showed that serine protease inhibitor B1 (SerpinB1) protects against ALI induced by orthotopic autologous liver transplantation. However, the role of SerpinB1 in lipopolysaccharide (LPS)-induced ALI and its regulatory mechanisms are not known. Wild-type (WT) and SerpinB1 knockout (KO) mice were treated with intratracheal LPS stimulation to induce ALI. Some of the WT and KO mice were injected i.p. with melatonin, a rhythm-related protein Rev-erbα agonist. The circadian rhythm in WT mice was disrupted by exposing mice to 24 h of continuous dark or light conditions after intratracheal LPS. Neutrophils were isolated from alveolar lavage fluid of WT and KO mice, and from human peripheral blood. Neutrophils were treated with LPS and melatonin. Disruption of circadian rhythm by either 24-h dark or light conditions exacerbated LPS-induced ALI and decreased expression of Rev-erbα and SerpinB1 protein in lung, whereas melatonin treatment increased SerpinB1 expression and attenuated LPS-induced ALI in WT mice, but not in KO mice. In isolated neutrophils, Rev-erbα was co-localized with SerpinB1 and bound to its promoter to trigger SerpinB1 transcription. Furthermore, LPS stimulation increased formation of neutrophil extracellular traps, which was reversed by melatonin treatment in neutrophils from WT mice, but not from KO mice. In mice, SerpinB1 is rhythmically regulated by Rev-erbα, and its down-regulation exacerbates LPS-induced ALI by inducing formation of neutrophil extracellular traps.

Shoots and Roots Induction of Garlic on Different Composition of Plant Growth Regulators and Photoperiod

Plant Growth Regulators and photoperiods will affect callus morphogenesis from garlic bulbils. The study aimed to obtain the best interaction between media composition and photoperiod for shoots and root induction of the garlic callus. The research has two-stage. The first stage consisted of two factors. The first factor is the combination of PGR for shoots induction which consists of three combinations, i.e., 0.1 ppm NAA + 1 ppm BAP, 2 ppm NAA + 2 ppm BAP, and 0.4 ppm 2,4-D + 2 ppm kinetin. The second factor is photoperiod which consists of 10, 16, and 22-h light conditions. The second stage is the root induction in different PGRs (2 ppm IBA and 0.2 ppm NAA + 2.25 ppm BA) under continuous dark conditions. The results of the first stage showed that the PGR produced the most shoots was 0.1 ppm NAA + 1 ppm BAP. After four weeks, the frequency of an explant emerging during the shoot reached 64% on media 0.1 ppm NAA + 1 ppm BAP. The treatment MS media supplemented with 0.1 ppm NAA + 1 ppm BAP at 16-h photoperiods increased the growth of shoots per explant in 11-15 shoots and produced the most extended shoot length. The result of the second stage showed that the number of roots on 2 ppm IBA is the same as NAA 0,2 ppm + BA 2,25 ppm, but the treatment 2 ppm IBA has the highest root number in three months.

Comparative Analysis of Glucosinolate and Phenolic Compounds in Green and Red Kimchi Cabbage (Brassica rapa L. ssp. pekinensis) Hairy Roots after Exposure to Light and Dark Conditions

Brassica rapa L. ssp. pekinensis (Lour.) Hanelt (kimchi cabbage) is a major vegetable cultivated in Korea, and its hairy roots (HRs) are rich in glucosinolates and phenolic compounds. This study aimed to induce HRs from cotyledon explants via the transformation of the Agroacterium rhizogenes strain R1000 and examine the glucosinolate and phenolic compounds present in the HRs of two kimchi cabbage (green and red) cultivars after exposure to 16 h light/8 h dark conditions (photosynthetic photon flux density of 54.6 µmol m−2 s−1) and continuous dark conditions. The highest HR production was achieved in the green kimchi cabbage grown under dark conditions (0.37 ± 0.01 DW g/30 mL). The highest glucosinolate and phenolic contents were neoglucobrassicin and catechin hydrate, which were highest in the green kimchi HRs grown under dark (GKHD) conditions (5268.29 ± 292.84 µg/g DW) and green HRs grown under light (GKHL) conditions (203.49 ± 4.70 µg/g DW), respectively. A heat map showed that the red kimchi HRs grown under dark conditions (RKHD) and the GKHL condition accumulated the highest glucosinolate and phenolic contents. Principal component (PCA) and partial least-squares discriminant (PLS-DA) analyses of the 13 identified metabolites showed a clear separation. According to a variable importance in projection (VIP) analysis, quercetin was the most important metabolite, leading to a clear separation. The most suitable conditions for enhancing the glucosinolate and phenolic contents were the GKHD and GKHL conditions, respectively, whereas both compounds were enhanced in the RKHD condition. HRs cultures cultivated under light and dark conditions are a promising method to enhance the production of specific health-promoting bioactive metabolites, which might be helpful in the pharmaceutical and nutraceutical industries.

Hepatopancreas immune response during different photoperiods in the Chinese mitten crab, Eriocheir sinensis

Photoperiod plays an important role in the growth, development, and metabolism of crustaceans. The growth and reproduction of crabs are closely related to the photoperiod. The hepatopancreas is an important source of innate immune molecules; however, hepatopancreatic patterns of gene expression depending on the photoperiod—which may underlie changes in immune mechanisms—remain unknown. To study the molecular basis of immune regulation in the Chinese mitten crab (Eriocheir sinensis) under different light conditions, a new generation of high-throughput Illumina sequencing technology was used, and functional genes associated with immune function in the hepatopancreas of this crab were explored via assembly of high-quality sequences, gene annotation, and classification. A total of 383,899,798 clean reads from the hepatopancreas of the normal group (12 h/12 h L:D), 387,936,676 clean reads from the continuous light group (24 h/0 h L:D), and 384,872,734 clean reads from the continuous darkness group (0 h/24 h L:D) were obtained. Compared with the normal group, 141, 152, 60, 87, 90, and 101 differentially expressed genes were identified in the groups exposed to continuous light for 2 days, continuous darkness for 2 days, continuous light for 4 days, continuous darkness for 4 days, continuous light for 6 days, and continuous darkness for 6 days, respectively. The results of this study revealed that under continuous light and dark conditions, the crabs were most affected by light on day 2, but the interference gradually decreased with time. We suggest that long-term light or dark treatment makes crabs adaptable to fluctuations in the photoperiod. The expression of genes associated with immune response patterns was found to change during different photoperiods. Prophenoloxidase (proPO) and serine proteinase (kazal-type serine proteinase inhibitor 1 and serine proteinase inhibitor-3) in the proPO-activating system were significantly upregulated in the 2-day continuous light group. Glutathione peroxidase 3 was significantly downregulated under continuous light exposure, while cyclooxygenase was upregulated in the continuous light and dark environments. These results provide insights into the molecular mechanism underlying the effects of the photoperiod on immune regulation and the physiological activity of E. sinensis.

CRISPR/Cas9-mediated knockout of period reveals its function in the circadian rhythms of the diamondback moth Plutella xylostella.

Circadian clocks control the rhythmicity of many behaviors and physiological features of insects. To study the circadian clock of the moth Plutella xylostella, we employed CRISPR/Cas9-mediated genome editing to investigate the effect of loss of the clock gene period on the circadian rhythms. P. xylostella harbors a single copy of period. Phylogenetic analysis showed that P. xylostella PERIOD is more homologous to mouse PERIOD than the PERIOD proteins from bees, flies, mosquitos, and many other Lepidoptera, such as Danaus plexippus and Bombyx mori. The circadian rhythms in adult locomotor activity were altered in the period knockout strain of P. xylostella under light-dark (LD) and continuous dark (DD) conditions. Under the LD cycle, the wild-type moths displayed nocturnal activity with activity peaking very early after lights off and quickly declining after lights on. In contrast, the period knockout strain had no peak in activity when the lights were turned off and exhibited steady activity throughout the hours of darkness. Interestingly, under DD conditions, our results showed that the locomotor rhythm can be maintained without period gene, but at a lower rhythmicity ratio than wild-type. In addition, knockout of period in P. xylostella changed circadian rhythms patterns related to pupal eclosion, mating, egg-laying, and egg hatching. Mechanistically, loss of PERIOD disrupted the molecular rhythm of period and changed the clock transcription rhythm in the heads of the moths under LD and DD conditions. Together, our study indicates that the PERIOD is required for normal expression of many behavioral rhythms in P. xylostella.

Floridean Starch and Floridoside Metabolic Pathways of Neoporphyra haitanensis and Their Regulatory Mechanism under Continuous Darkness.

Floridean starch and floridoside are the main storage carbohydrates of red algae. However, their complete metabolic pathways and the origin, function, and regulatory mechanism of their pathway genes have not been fully elucidated. In this study, we identified their metabolic pathway genes and analyzed the changes in related gene expression and metabolite content in Neoporphyra haitanensis under continuous dark conditions. Our results showed that genes from different sources, including eukaryotic hosts, cyanobacteria, and bacteria, were combined to construct floridean starch and floridoside metabolic pathways in N. haitanensis. Moreover, compared with those in the control, under continuous dark conditions, floridean starch biosynthesis genes and some degradation genes were significantly upregulated with no significant change in floridean starch content, whereas floridoside degradation genes were significantly upregulated with a significant decrease in floridoside content. This implies that floridean starch content is maintained but floridoside is consumed in N. haitanensis under dark conditions. This study elucidates the “floridean starch–floridoside” metabolic network and its gene origins in N. haitanensis for the first time.

Earthworm Depuration: Analysis of Coprophagy and Light Impacts

Earthworms are used as biomarkers to determine the bioavailability of contaminants. As such, their uptake of contaminants has been studied extensively. Protocols have been established to ensure that laboratory-obtained data are valid and comparable. However, the method of removing the organism’s gut content (depuration) before assessing the contaminant in the tissue is not standardized. The aim of this research project is to investigate some parameters for earthworm depuration: light conditions and coprophagy prevention. Eisenia fetida were depurated for 48 hours in two separate studies according to guidelines ASTM-E1676 and OECD Test No. 317. In one study, 2 frequencies of egesta removal were employed during depuration to prevent coprophagy and compared to the control (egesta and worms removed after 48 hours). In another study, the subjects and material egested were assessed under conditions of continuous darkness and the control (continuous light). The depuration methods that included egesta removal every 12 and 24 hours resulted in 62% and 10% more egested material per mg of earthworm than the control (filter paper disc change after 48 hours), respectively. The earthworms depurated in continuous darkness egested 94% more material per mg of earthworm than the control. The results indicate that depuration would be more total under continuous darkness and employing a coprophagy prevention method. These findings could lead to more efficient depuration methods.

Effects of Biotin and Ascorbic Acid Applications on Haploid Embryo Induction in Semisolid and Double Layer Nutrient Media in Pepper (Capsicum annuum L.) Anther Culture

Generation of homozygous double haploid (DH) lines by androgenesis is a promising alternative to selfpollination programs across generations. Despite the routine use of anther culture in peppers, there are still many bottlenecks and improvements in methodology are required. The aim of this study was to determine the effects of the structure of the nutrient medium (semi-solid and double layer) and the addition of biotin and ascorbic acid to the nutrient media on obtaining haploid embryos by anther culture method. MS (Murashige and Skoog 1962) medium containing 4 mg l-1 NAA, 0.1 mg l-1 BAP, 0.25% activated charcoal, 30 g l-1 sucrose, and 10 mg l-1 AgNO3 (silver nitrate) were used as the basal nutrient medium. A total of 8 nutrient media compounds were studied using 0.05 mg l-1 biotin and 0.5 mg l-1 ascorbic acid separately or together in semi-solid and bi-layer (double-phase) nutrient media. Solidification of nutrient media was achieved with 7 g 1-1 agar. The cultured anthers were subjected to high-temperature pre-treatments at 35 °C in continuous dark conditions for 2 days. Then they were taken to a climate chamber at of 25 °C temperature adjusted to 16/8 hour photoperiod. It has been observed that the success of obtaining embryos of semi-solid medium was higher than double-layer medium. The addition of biotin and ascorbic acid to the nutrient medium provided 8.8 fold increases in embryo regeneration compared to the control medium. In the presence of only one of biotin or ascorbic acid in the nutrient medium, the number of embryos increased compared to the control.

Expression and function analysis of FaCO gene in Festuca arundinacea

Photoperiod plays an important role in transformation from vegetative growth to reproductive growth in plants. CONSTANS (CO), as a unique gene in the photoperiod pathway, responds to changes of day length to initiate flowering in the plant. In this study, the expression level of FaCONSTANS (FaCO) gene under long-day, short-day, continuous light and continuous darkness conditions was analyzed by real-time quantitative PCR. We constructed the over-expression vector p1300-FaCO and infected into Arabidopsis thaliana by Agrobacterium-mediated method. We constructed the silencing vector p1300-FaCO-RNAi and infected into Festuca arundinacea by Agrobacterium-mediated method. The expression of FaCO gene was regulated by photoperiod. The over-expression of FaCO promoted flowering in wild type of Arabidopsis thaliana under long day condition and rescued the late flowering phenotype in co-2 mutant of Arabidopsis thaliana. Silencing FaCO gene in Festuca arundinacea by RNAi showed late-flowering phenotype or always kept in the vegetative growth stage. Our understanding the function of FaCO in flowering regulation will help further understand biological function of this gene in Festuca arundinacea.

Development and characterization of flower and capsule in Borneo jewel orchid Macodes limii J.J. Wood and A.L. Lamb (Orchidaceae: Asparagales)

Macodes limii J.J. Wood & A.L. Lamb is an endemic jewel orchid of Sabah in Borneo. The species has unique characteristic with high potential to be commercialized as ornamental plant. However, it was understudied due to its scarcity in nature, which can only be found at certain area in Sabah with ultramafic soil. To understand the reproduction biology of this species, the present study was conducted to document the developmental stages of flower and capsule to determine the right harvesting time for further use in seed germination study. Macodes limii was collected from its natural habitat and cultivated ex situ throughout this study. Flower development was recorded starting from inflorescence initiation until full bloom, which took over 54 days to complete. Flower was artificially pollinated, and capsule was produced within 22 days, and harvesting was performed prior to dehiscence. Seeds were aseptically cultured on half-strength Murashige and Skoog medium + 3% (w/v) sucrose, and 29% of seeds were successfully germinated after 24 weeks under continuous dark condition. The current findings are beneficial as a reference to support the conservation efforts of this endemic species.

Induced Thermo-dormancy in Rapeseed (Brassica napus L.) Cultivars by Sub- and Supra-optimal Temperatures

Till now the impacts of sub- and supra-optimal temperatures on the induction of secondary dormancy (SD) in rapeseed seeds have not yet been investigated. Therefore, the possibility of SD induction at sub- and supra-optimal temperatures (thermo-dormancy) was investigated in six rapeseed cultivars with high (Trapper and Agamax), medium (Hayola-50 and Hayola-420) and low (Rohan and Zarfam) SD potential. Seeds were incubated at 5, 10, 15, 20, 25, 30, 35, 37 and 40 °C under both light (12 h light/12 h dark) and continuous dark conditions to assess for thermo-dormancy induction. Thermo-dormancy in high SD potential cultivars was more than 90% at 5, 37 and 40 °C in the dark. The cultivars with medium SD potential only displayed high level of thermo-dormancy (> 70%) at 37 and 40 °C, but at 5 °C it was less than 25% in the dark. In high and medium SD cultivars, light stimulated germination and reduced thermo-dormant seeds at sub- and supra-optimal temperatures. In the low SD cultivars, which displayed very low percentages of thermo-dormancy and thermo-inhibition of germination at sub- and supra-optimal temperatures, seed mortality increased with rise of temperature. Accordingly, the reduced germination of rapeseed at sub- and supra-optimal temperatures may be due to thermo-inhibition, thermo-dormancy and seed mortality, which are also affected by light condition. Use of seeds with low potential for SD induction from tolerant cultivars in environments prone to temperature stress and/or adopting suitable planting date to increase crop establishment under stressful environments are recommended.

Photosynthetic fluctuation accompanied by translocation of chloroplasts in Ulva conglobata (Ulvophyceae) grown under a low irradiance regime

SUMMARYFluctuations in photosynthetic characteristics related to chloroplast translocation have been known in the foliose green algae Ulva lactuca var. latissima and var. rigida and U. mutabilis according to photoperiod. In Ulva, the single parietal chloroplast is found along the thallus surface wall and exhibits high photosynthetic activity during the light period; the chloroplast then moves towards the side walls and shows low photosynthetic activity during the dark period. In this study, we re‐investigated whether the photosynthetic ability is dependent on chloroplast location in a unialgal culture of U. conglobata grown and maintained under low irradiance regime by analyzing in vivo absorption spectra, oxygen evolution, and pulse amplitude modulation chlorophyll fluorescence. The light absorbance of the thallus was higher when chloroplast was along the thallus surface wall than when along the side walls and, therefore, the thallus absorbance at 680 nm was used as an index of chloroplast position. Some photosynthetic parameters such as maximum net photosynthetic rate per thallus area and effective quantum yield of photosystem II correlated with the thallus absorbance. The highest rate and absorption were reached 3 to 9 h after the beginning of light period (12 h), which gradually decreased at 10 to 15 h after the beginning of light or dark period. The lowest rate and absorption was observed after the beginning of the dark period. The chloroplast movement was inhibited for 12 h by colchicine, and photosynthetic parameters were found to be dependent on various chloroplast positions in the thallus. Interestingly, the chloroplast moved to the surface and the side walls of the cells under continuous dark and light conditions, respectively, at approximately 48 to 72 h. However, decreased maximum quantum yield was observed under both continuous dark and light conditions.

Physiological variability of Fusarium verticillioides causing post flowering stalk rot in maize

Post flowering stalk rot of maize caused by Fusarium verticillioides is the major disease and the occurrence of variability in the pathogen is one of the key factors for difficulty in management of the disease. The effect of temperature regimes showed the maximum radial growth and highest sporulation was obtained at 30℃ by all six isolates of F. verticillioides. At pH 7 maximum radial growth of all isolates was obtained except FV 1 and FV 7 isolates which produced maximum radial growth at pH 6. Highest sporulation of all six isolates was seen at pH 6. Exposure of pathogen to continuous dark (24 hours) condition yielded maximum radial growth in all isolates except in FV 6 isolate which produced maximum radial growth when it was exposed to continuous light (24 hours). Optimum sporulation of all the six isolates was seen under continuous dark condition followed by alternate cycles of 12 hours light and 12 hours darkness. Isolates FV 2 and FV 7 were produced maximum radial growth on soluble starch, whereas FV 3 and FV 6 isolates on sucrose. Fructose and maltose produced maximum radial growth of FV 1 and FV 5 isolate respectively. Optimum sporulation of all six isolates was obtained by supplying fructose and sucrose as carbon source.

Temperature-dependent development and survival of small hive beetle, Aethina tumida (Coleoptera: Nitidulidae)

The small hive beetle (SHB) Aethina tumida Murray, (Coleoptera: Nitidulidae) is an invasive pest of honey bees recently found in Korea. We investigated the influence of temperature on the development and survival of immature SHBs. The beetle’s immature stages were exposed to different constant temperatures (15, 20, 25, 30, 35, 37 and 39 °C) under stable and continuous dark conditions and a relative humidity of 75 ± 5%. All immature stages successfully developed to the next stage at the temperature range from 15 to 39 °C, except for the egg at 15 °C and wandering larvae and pupae, which suffered 100% mortalities at 39 °C. Total immature developmental period at 18.6 and 35 °C ranged from 53.9 days to 20, respectively. Lower developmental thresholds were determined according to a linear model as 16.0, 11.6, 9.6, 12.6, and 11.8 °C for eggs, feeding larvae, wandering larvae, pupae and total immatures, respectively. Among the non-linear models, Analytis-3/Briere-1 was selected as the best to describe the temperature-dependent developmental rate of all immature stages of SHBs based on Akaike information criterion corrected (AICc) values and biological adequacy. According to this model, optimum and high developmental threshold temperatures for eggs, feeding larvae, wandering larvae, pupae and total immatures were 39.1, 36.5, 33.2, 35.5, and 34.8 °C and 46.5, 44, 40.4, 42.5 and 41.5 °C, respectively. According to the polynomial regression model, maximum survival was estimated at temperatures of 28.2, 28.7, 26.7 and 26.5 °C, of eggs, feeding larvae, wandering larvae and pupae, respectively. This study can be used to predict the potential distribution of SHB in non-native locations.