Starvation Stress Research Articles

Start-up and Recovery Performance of ANAMMOX Reactors Under Long-term Starvation

The application of ANAMMOX technology is constrained by sluggish growth and difficulty in enriching ANAMMOX bacteria. Long-term starvation of functioning bacteria due to limited substrate supply makes the steady operation of ANAMMOX reactors more difficult. Re-examining the start-up and recovery performance of the ANAMMOX reactor and identifying its resistance mechanism are important from the standpoint of long-term starvation. By inoculating nitrifying and denitrifying sludge under various operating circumstances, the ANAMMOX reactors were successfully started. Under various start-up procedures, the tolerance mechanism and recovery performance were examined. The outcomes demonstrated that the denitrifying sludge-inoculated reactor operated steadily with a high substrate concentration and low flow rate. After 85 days of operation, the removal efficiencies of NH4+-N, NO2--N, and total nitrogen reached 98.7%, 99.3%, and 89.3%, respectively. After 144 days of starvation and 30 days of recovery, the better nitrogen removal performance was achieved at a low substrate concentration and high flow rate, and the removal efficiencies were 99.8% （NH4+-N）, 99.8% （NO2--N）, and 93.6% （total nitrogen）. During the starvation, extracellular polymeric substances wrapped the ANAMMOX bacteria and kept them intact to resist long-term starvation stress. The expression of nirS, hzsA, and hdh genes ensured the synthesis of nitrite/nitric oxide oxidoreductase, hydrazine synthase, and hydrazine dehydrogenase to maintain ANAMMOX activity. There was no significant difference in the relative abundance of ANAMMOX bacteria before and after starvation recovery. Candidatus Kuenenia had better anti-hunger ability, and the relative abundance increased by more than 86% after 30 days of recovery, confirming its tolerance to long-term starvation.

Natural variation in starvation sensitivity maps to a point mutation in phospholipase IPLA2-VIA in Drosophila melanogaster.

Resistance to starvation is a classic complex trait, where genetic and environmental variables can greatly modify an animal's ability to survive without nutrients. In this study, we investigate the genetic basis of starvation resistance using complementary quantitative and classical genetic mapping in Drosophila melanogaster. Using the Drosophila Genetics Reference Panel (DGRP) as a starting point, we queried the genetic basis of starvation sensitivity in one of the most sensitive DGRP lines. We localize a major effect locus modifying starvation resistance to the phospholipase iPLA2-VIA. This finding is consistent with the work of others which demonstrate the importance of lipid regulation in starvation stress. Furthermore, we demonstrate that iPLA2-VIA plays a role in the maintenance of sugar reserves post-starvation, which highlights a key dynamic between lipid remodeling, sugar metabolism and resistance to starvation stress.

Respiration rate and intestinal microbiota as promising indicators for assessing starvation intensity and health status in Pacific oyster (Crassostrea gigas)

Implementing early disease warning is vital to prevent large-scale mortality of mollusks cultured in open waters. Starvation-induced emaciation syndrome is an undeniable prerequisite for mollusk mortality. Nevertheless, the indicators of mollusk response to starvation remain poorly understood. In this study, the effects of a 44-day starvation period on the physiological performance and symbiotic microbiota of oysters were investigated. Starvation resulted in reduced growth and survival and notable damage to intestinal structure, including shrinking lumens and shortened intestinal walls and villi. Analyses of the respiration rate and intestinal microbiota, including OTUs, taxonomy, and predicted functions, revealed a stepped change pattern with a tipping point on day 10, indicating that oysters employed distinct strategies to adapt to prolonged starvation. Biomarkers associated with nutrient digestion and uptake, such as Firmicutes and Staphylococcus abundance, as well as the Firmicutes/Bacteroidetes ratio, progressively declined with increasing starvation. Conversely, Proteobacteria, an indicator of energy disequilibrium and unstable gut microbiota, and pathogenic Vibrio, showed significant enrichment. As starvation progressed, bacterial competition intensified, as evidenced by the reduced network connectivity and the increasing percentage of negative correlations. Functional predictions demonstrated an early-stage enrichment of degradation functions followed by later-stage suppression during prolonged starvation. In contrast, biosynthesis functions exhibited the opposite trend, suggesting that intestinal microbiota adjusted their specific functions to cope with food deprivation. Collectively, a conceptual model of starvation stress tolerance limits (SSTL) was introduced to define critical thresholds and candidate markers for evaluating starvation intensity and oyster health. This study offers valuable insights into non-feeding mollusks' adaptation to prolonged starvation and provides potential indicators for mollusk mortality events.

Starvation-induced changes in the proteome and transcriptome of the salivary glands of leech (Hirudo nipponia).

Hirudo nipponia is an important medicinal animal in China. Its salivary gland secretions contain a variety of protein bioactive substances. Investigations of its salivary glands are of great significance in the study of the medicinal value and mechanism of leech secretions. Illumina RNA-Seq technology was used to perform transcriptome sequencing of salivary gland tissue of H. nipponia under starvation (D30) and fed (D0) states. A total of 2,650 differentially expressed genes (DEGs) were screened. Using the label-free protein quantification technique and bioinformatics analysis, the expression of differentially expressed proteins (DEPs) in the salivary gland tissue of H. nipponia was compared. A total of 2,021 proteins were identified, among which 181 proteins were differentially expressed between the starvation and fed states, with 72 significantly upregulated and 109 significantly downregulated. The salivary glands of H. nipponia synthesized protein-based active substances after 30 days of starvation and adapted to the starvation environment by weakening respiratory activity and reducing metabolic activity to reduce energy expenditure. Energy was produced by glycolysis and the tricarboxylic acid cycle for the synthesis of substances such as antibiotics. This study combined transcriptome and proteome sequencing data to provide a data reference for an in-depth study of the regulatory mechanism of salivary gland secretions of H. nipponia under starvation stress by analyzing DEGs and DEPs.

Comparative physiological, biochemical and transcriptomic analyses to reveal potential regulatory mechanisms in response to starvation stress in Cipangopaludina chinensis

Cipangopaludina chinensis, as a financially significant species in China, represents a gastropod in nature which frequently encounters starvation stress owing to its limited prey options. However, the underlying response mechanisms to combat starvation have not been investigated in depth. We collected C. chinensis under several times of starvation stress (0, 7, 30, and 60 days) for nutrient, biochemical characteristics and transcriptome analyses. The results showed that prolonged starvation stress (> 30 days) caused obvious fluctuations in the nutrient composition of snails, with dramatic reductions in body weight, survival and digestive enzyme activity (amylase, protease, and lipase), and markedly enhanced the antioxidant enzyme activities of the snails. Comparative transcriptome analyses revealed 3538 differentially expressed genes (DEGs), which were significantly associated with specific starvation stress-responsive pathways, including oxidative phosphorylation and alanine, aspartate, and glutamate metabolism. Then, we identified 40 candidate genes (e.g., HACD2, Cp1, CYP1A2, and GPX1) response to starvation stress through STEM and WGCNA analyses. RT-qPCR verified the accuracy and reliability of the high-throughput sequencing results. This study provides insights into snail overwintering survival and the potential regulatory mechanisms of snail adaptation to starvation stress.

Molecular characterization and expression analysis of six small heat shock protein genes in Trogoderma granarium during cold and starvation-induced larval diapause

The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a highly invasive pest infesting stored grains, cereal products, and is recognised as a quarantine pest in many countries. Various stressors can instigate prolonged diapause among insect larvae, increasing the challenge of managing infestation. When the environmental conditions become conducive to development, diapause ceases, and the larva progresses on its developmental course. Members of the Heat Shock Protein (HSP) family play a significant role in protecting insects from the impacts of environmental stressors. In this study, six small heat shock proteins (TsHSP19.8, TsHSP20.5, TsHSP20.6, TsHSP20.8, TsHSP21.2, and TsHSP21.3) were identified and characterized in T. granarium. Transcript abundances of TsHSPs were analysed across distinct phases of larval diapause induced by both cold exposure and starvation stress treatments, alongside various developmental stages. The gene expression patterns of TsHSP20.5 and TsHSP21.2 exhibited peak mRNA levels during pre-diapause following the cold treatment, while the greatest abundances of TsHSP19.8, TsHSP20.6, TsHSP20.8, and TsHSP21.3 were detected in the diapause phases. The highest mRNA abundances of TsHSP20.5, TsHSP20.8, TsHSP21.2, and TsHSP21.3 were observed during the diapause phase following the starvation treatment, while it was noted on the first day of the post-diapause phase for TsHSP19.8 and TsHSP20.6. The remarkable levels of TsHSPs during diapause might imply their putative role in cold and starvation survival. Significant expression of TsHSP19.8, TsHSP20.6, TsHSP20.8, and TsHSP21.3 transcripts was observed in adults, suggesting their potential involvement in developmental processes. Understanding the genetic mechanisms involved in the diapause physiology of T. granarium could offer additional insights for the integrated management of this pest.

DarA-the central processing unit for the integration of osmotic with potassium and amino acid homeostasis in Bacillus subtilis.

Cyclic di-adenosine monophosphate (c-di-AMP) is a second messenger involved in diverse metabolic processes including osmolyte uptake, cell wall homeostasis, as well as antibiotic and heat resistance. This study investigates the role of the c-di-AMP receptor protein DarA in the osmotic stress response in Bacillus subtilis. Through a series of experiments, we demonstrate that DarA plays a central role in the cellular response to osmotic fluctuations. Our findings show that DarA becomes essential under extreme potassium limitation as well as upon salt stress, highlighting its significance in mediating osmotic stress adaptation. Suppressor screens with darA mutants reveal compensatory mechanisms involving the accumulation of osmoprotectants, particularly potassium and citrulline. Mutations affecting various metabolic pathways, including the citric acid cycle as well as glutamate and arginine biosynthesis, indicate a complex interplay between the osmotic stress response and metabolic regulation. In addition, the growth defects of the darA mutant during potassium starvation and salt stress in a strain lacking the high-affinity potassium uptake systems KimA and KtrAB can be rescued by increased affinity of the remaining potassium channel KtrCD or by increased expression of ktrD, thus resulting in increased potassium uptake. Finally, the darA mutant can respond to salt stress by the increased expression of MleN , which can export sodium ions.IMPORTANCEEnvironmental bacteria are exposed to rapidly changing osmotic conditions making an effective adaptation to these changes crucial for the survival of the cells. In Gram-positive bacteria, the second messenger cyclic di-AMP plays a key role in this adaptation by controlling (i) the influx of physiologically compatible organic osmolytes and (ii) the biosynthesis of such osmolytes. In several bacteria, cyclic di-adenosine monophosphate (c-di-AMP) can bind to a signal transduction protein, called DarA, in Bacillus subtilis. So far, no function for DarA has been discovered in any organism. We have identified osmotically challenging conditions that make DarA essential and have identified suppressor mutations that help the bacteria to adapt to those conditions. Our results indicate that DarA is a central component in the integration of osmotic stress with the synthesis of compatible amino acid osmolytes and with the homeostasis of potassium, the first response to osmotic stress.

Microbiome origin and stress-related changes in bacterial abundance of the photosymbiotic sea slug Berghia stephanieae (Á. Valdés, 2005)

The precise mechanisms that allow animals and phototrophic organisms to form a stable photosymbiotic relationship are still unknown. While previous studies focused on genomic adaptations of the animal host, more recent research looked into the role of bacteria in photosymbiosis. Here, we analyzed the core microbiome of the sea slug Berghia stephanieae and its food source Exaiptasia diaphana to understand if the microbiome and the linked bacterial metabolic pathways differ between unstable and stable photosymbiosis. This sea slug feeds solely on the model cnidarian E. diaphana and steals their photobionts which the slug can only maintain for a week. We additionally examined the influence of light and starvation stress on the slug’s bacterial composition, which are common experimental set-ups to elucidate the photosymbiotic relationship in the slugs. Our results show that the core microbiome of B. stephanieae and E. diaphana differed significantly suggesting that the slug’s microbiome is not obtained from its food source or the water column and indicates a vertical transmission. Further, differences in metabolic pathways imply that the microbiome of B. stephanieae does not support a stable photosymbiosis due to an insufficient nitrogen cycle on part of the photobiont. Starving the slugs induced a shift towards an increased abundance of potential pathogens and led to a downregulation in the sulphur cycle. Yet, starvation in darkness resulted in the depletion of most bacteria and induced a metabolic switch toward bacterial nitrogen fixation. This emphasizes that different holobiont members contribute to essential nutrient cycles, and it is important to look beyond the photobiont to understand the sea slug holobiont.

Sea cucumber (Acaudina leucoprocta) peptides exhibit anti-aging effect in Drosophila melanogaster via regulation of microbiota dysbiosis and metabolic disorder

As the population ages, the pursuit of extended lifespan and improved healthspan has gained significance. This study assessed the anti-aging properties of sea cucumber peptides derived from Acaudina leucoprocta (SCP) through microbiome and metabolome analyses in Drosophila melanogaster. Supplementation with 0.2%, 0.4%, 0.6%, and 0.8% of SCP significantly boosted the survival rate and extended the mean and median lifespans in both male and female flies. Among them, 0.6% SCP treatment extended the mean and median lifespans of male flies by 21.01% and 25.48 %, which showed the most prominent lifespan-prolonging effect. Moreover, SCP enhanced the healthspan of male flies by improving their climbing ability, intestinal barrier function, and memory performance. Additionally, SCP boosted the survival rate of flies subjected to oxidative, starvation, and heat stress, with no significant effect observed under cold stress conditions. The lifespan-extension effect of SCP remained unaffected by dietary restriction, but was partially inhibited when provided with antibiotic-supplemented food. SCP modulated microbiota with increased the abundance of Lactobacillus, Rhodococcus, and Propioniciclava and decreased Acetobacter, Achromobacter, Pedobacter, and norank_f_Saprospiraceae, which closely related with lifespan-extension effect. Furthermore, SCP induced a metabolic profile in 30-day-old flies more akin to that of 3-day-old flies, impacted 13 significantly regulated metabolites associated with amino acid, nucleotide, and carbohydrate metabolisms. These findings highlight SCP intervention as a promising anti-aging strategy.

The phenomenon of attachment and feeding of unfed ticks (Ixodoidea) on fed and feeding specimens of the same or different species: biological and epidemiological issues

Hyperparasitism, characterized by attachment and feeding of unfed ticks on engorged or feeding specimens of the same species (tick-to-tick attachment and feeding) has been extensively documented in laboratory colonies of ticks of the Ixodoidea superfamily. Existing literature generally assumes that hyperparasitism operates similarly across tick species in both main families, Argasidae and Ixodidae. However, a closer examination of the available data reveals distinct biological mechanisms underlying this phenomenon in different groups. In argasid ticks, hyperparasitism in laboratory colonies primarily involves unfed specimens stealing blood from their fed relatives, especially under stress of starvation or overcrowding. It remains uncertain whether this behavior of argasid ticks occurs under field conditions. If it does happen naturally, it may have originated as a consequence of the nidicolous lifestyle exhibited by soft ticks. In Ixodes ticks (Ixodinae or Prostriata), hyperparasitism of males on unfed or feeding females appears to be a side-effect in the male attempts to copulate while hyperparasitism in Amblyomminae (Metastriata) ticks is likely an aberration in feeding. This difference between Argasidae and Ixodidae may stem from independent adaptation to blood-feeding within the two Ixodoidea families. Experimental evidence of pathogen transmission between aggressor and victim during hyperparasitic feeding has only been demonstrated under laboratory conditions specifically in Ornithodoros species (Argasidae). The practical importance of this route of pathogen transmission is still unclear. Although there is an assumption in the literature that hyperparasitic pathogen transmission occurs in the taiga tick Ixodes persulcatus, it is important to know that no current data is available to support this presumption.

A Hemoglobin Bionics-Based System for Combating Antibiotic Resistance in Chronic Diabetic Wounds via Iron Homeostasis Regulation.

Owing to the increased tissue iron accumulation in patients with diabetes, microorganisms may activate high expression of iron-involved metabolic pathways, leading to the exacerbation of bacterial infections and disruption of systemic glucose metabolism. Therefore, an on-demand transdermal dosing approach that utilizes iron homeostasis regulation to combat antimicrobial resistance is a promising strategy to address the challenges associated with low administration bioavailability and high antibiotic resistance in treating infected diabetic wounds. Here, it is aimed to propose an effective therapy based on hemoglobin bionics to induce disturbances in bacterial iron homeostasis. The preferred "iron cargo" is synthesized by protoporphyrin IX chelated with dopamine and gallium (PDGa), and is delivered via a glucose/pH-responsive microneedle bandage (PDGa@GMB). The PDGa@GMB downregulates the expression levels of the iron uptake regulator (Fur) and the peroxide response regulator (perR) in Staphylococcus aureus, leading to iron nutrient starvation and oxidative stress, ultimately suppressing iron-dependent bacterial activities. Consequently, PDGa@GMB demonstrates insusceptibility to genetic resistance while maintaining sustainable antimicrobial effects (>90%) against resistant strains of both S. aureus and E. coli, and accelerates tissue recovery (<20 d). Overall, PDGa@GMB not only counteracts antibiotic resistance but also holds tremendous potential in mediating microbial-host crosstalk, synergistically attenuating pathogen virulence and pathogenicity.

Deleterious effects of the endosymbiont Rickettsiella viridis in Myzus persicae are environmentally dependent

AbstractEndosymbionts living within insect cells can modify host fitness and could provide new tools for pest control. The endosymbiont Rickettsiella viridis has been transferred experimentally into the green peach aphid, Myzus persicae, a globally important agricultural pest. This Rickettsiella spreads via vertical and horizontal transmission and induces host fitness costs which could potentially suppress pest populations. Endosymbiont prevalence can fluctuate in natural populations, and it is important to identify factors that contribute to their spread or loss. Here, we explore the effects of Rickettsiella infection when aphids are reared on eight different host plants or exposed to thermal, starvation and desiccation stresses. Rickettsiella infection reduced M. persicae fecundity and longevity across all host plants, but the magnitude of costs varied among host plants and generations. Rickettsiella was horizontally transmitted and spread in caged populations at initial ratios of 1:2 Rickettsiella (+): Rickettsiella (−) on all host plants, but with limited long-term persistence under cycling 20–30 °C. We also identified temperature-dependent costs of Rickettsiella infection on heat knockdown time, chill coma recovery, and starvation tolerance. Finally, we present evidence that Rickettsiella infection reduces host activity levels under heat stress. Our results suggest that Rickettsiella infections induce a variety of deleterious effects but with complex environment-dependent interactions. This work helps understand ecological conditions that enhance or limit the spread of these endosymbionts in aphid populations.

Differentiation granules, a dynamic regulator of T. brucei development.

Adaptation to a change of environment is an essential process for survival, in particular for parasitic organisms exposed to a wide range of hosts. Such adaptations include rapid control of gene expression through the formation of membraneless organelles composed of poly-A RNA and proteins. The African trypanosome Trypanosoma brucei is exquisitely sensitive to well-defined environmental stimuli that trigger cellular adaptations through differentiation events that characterise its complex life cycle. The parasite has been shown to form stress granules in vitro, and it has been proposed that such a stress response could have been repurposed to enable differentiation and facilitate parasite transmission. Therefore, we explored the composition and positional dynamics of membraneless granules formed in response to starvation stress and during differentiation in the mammalian host between the replicative slender and transmission-adapted stumpy forms. We find that T. brucei differentiation does not reflect the default response to environmental stress. Instead, the developmental response of the parasites involves a specific and programmed hierarchy of membraneless granule assembly, with distinct components and regulation by protein kinases such as TbDYRK, that are required for the parasite to successfully progress through its life cycle development and prepare for transmission.

Characterization of three lamp genes from largemouth bass (Micropterus salmoides): molecular cloning, expression patterns, and their transcriptional levels in response to fast and refeeding strategy.

Lysosomes-associated membrane proteins (LAMPs), a family of glycosylated proteins and major constituents of the lysosomal membranes, play a dominant role in various cellular processes, including phagocytosis, autophagy and immunity in mammals. However, their roles in aquatic species remain poorly known. In the present study, three lamp genes were cloned and characterized from Micropterus salmoides. Subsequently, their transcriptional levels in response to different nutritional status were investigated. The full-length coding sequences of lamp1, lamp2 and lamp3 were 1251bp, 1224bp and 771bp, encoding 416, 407 and 256 amino acids, respectively. Multiple sequence alignment showed that LAMP1-3 were highly conserved among the different fish species, respectively. 3-D structure prediction, genomic survey, and phylogenetic analysis were further confirmed that these genes are widely existed in vertebrates. The mRNA expression of the three genes was ubiquitously expressed in all selected tissues, including liver, brain, gill, heart, muscle, spleen, kidney, stomach, adipose and intestine, lamp1 shows highly transcript levels in brain and muscle, lamp2 displays highly expression level in heart, muscle and spleen, but lamp3 shows highly transcript level in spleen, liver and kidney. To analyze the function of the three genes under starvation stress in largemouth bass, three experimental treatment groups (fasted group and refeeding group, control group) were established in the current study. The results indicated that the expression of lamp1 was significant induced after starvation, and then returned to normal levels after refeeding in the liver. The expression of lamp2 and lamp3 exhibited the same trend in the liver. In addition, in the spleen and the kidney, the transcript level of lamp1 and lamp2 was remarkably increased in the fasted treatment group and slightly decreased in the refed treatment group, respectively. Collectively, our findings suggest that three lamp genes may have differential function in the immune and energetic organism in largemouth bass, which is helpful in understanding roles of lamps in aquatic species.

Exploring the sex dimorphism in the expression of intestinal barrier and immune-related genes and intestinal microbiota in cage-cultured large yellow croaker (Larimichthys crocea) during the overwintering period along the Zhoushan coast

In Zhejiang province, large yellow croakers are primarily cultured in net cages, facing significant challenges during the overwintering period such as susceptibility to cold and starvation stress. Notably, the observable sexual dimorphism in the large yellow croaker hints at the likelihood of gender differences in their responses to these environmental stresses. However, the potential sex-specific adaptive changes during overwintering remain unexplored. To gain deeper insights, we investigated the expression of intestinal barrier-related genes, immune responses, and changes in intestinal microbiota during the overwintering period in males and females separately. The results revealed a more pronounced loss of body weight in females than that in males. In male intestines, there was a significant decrease in the expression of intestinal barrier-related genes (arp2/3, occludin, and zo1), contrasting with a significant increase in females. The expression of TLR1, TLR3, TLR7, TLR9, MyD88, and NF-κB genes in the intestines of female fish decreased significantly in March compared to November, while the opposite trend was observed in male fish. However, in the liver, TLR1, TLR3, TLR7, TLR9, MyD88, and NF-κB genes expression were both decreased significantly in males and females. In the male intestines, there was a significant increase in the expression of inflammatory cytokine genes (IL-1β and IL-6). In the females, IL-1β gene expression significantly decreased, while IL-6 expression increased significantly. The expression of IL-10 genes decreased in both males and females. In the liver, both the males and females exhibited a significant increase in the expression of IL-1β and IL-6 genes. Further analysis revealed greater susceptibility of male intestinal microbiota diversity during the overwintering period. Firmicutes’ relative abundance exhibited opposing changes between the males and females, and Proteobacteria abundance, driven by a significant increase in Vibrio bacteria, significantly increased in the males. In conclusion, the overwintering period may compromise the structural integrity of male fish intestines, reducing their immune function. Additionally, the response strategy of the intestinal microbiota differs between sexes. The findings provide crucial insights for crafting effective strategies and management decisions in cage-cultured large yellow croaker during the overwintering period, as well as offering theoretical references for monosex aquaculture.

Effect of arbuscular mycorrhizal symbiosis on growth and biochemical characteristics of Chinese fir (Cunninghamia lanceolata) seedlings under low phosphorus environment.

The continuous establishment of Chinese fir (Cunninghamia lanceolata) plantations across multiple generations has led to the limited impact of soil phosphorus (P) on tree growth. This challenge poses a significant obstacle in maintaining the sustainable management of Chinese fir. To investigate the effects of Arbuscular mycorrhizal fungi (AMF) on the growth and physiological characteristics of Chinese fir under different P supply treatments. We conducted an indoor pot simulation experiment in the greenhouse of the Forestry College of Fujian Agriculture and Forestry University with one-and-half-year-old seedlings of Chinese fir from March 2019 to June 2019, with the two P level treatment groups included a normal P supply treatment (1.0 mmolL-1 KH2PO4, P1) and a no P supply treatment (0 mmolL-1 KH2PO4, P0). P0 and P1 were inoculated with Funneliformis mosseae (F.m) or Rhizophagus intraradices (R.i) or not inoculated with AMF treatment. The AMF colonization rate in the root system, seedling height (SH), root collar diameter (RCD) growth, chlorophyll (Chl) photosynthetic characteristics, enzyme activities, and endogenous hormone contents of Chinese fir were estimated. The results showed that the colonization rate of F.m in the roots of Chinese fir seedlings was the highest at P0, up to 85.14%, which was 1.66 times that of P1. Under P0 and P1 treatment, root inoculation with either F.m or R.i promoted SH growth, the SH of R.i treatment was 1.38 times and 1.05 times that of F.m treatment, respectively. In the P1 treatment, root inoculation with either F.m or R.i inhibited RCD growth. R.i inhibited RCD growth more aggressively than F.m. In the P0 treatment, root inoculation with F.m and R.i reduced the inhibitory effect of phosphorus deficiency on RCD. At this time, there was no significant difference in RCD between F.m, R.i and CK treatments (p < 0.05). AMF inoculation increased Fm, Fv, Fv/Fm, and Fv/Fo during the chlorophyll fluorescence response in the tested Chinese fir seedlings. Under the two phosphorus supply levels, the trend of Fv and Fm of Chinese fir seedlings in different treatment groups was F.m > R.i > CK. Under P0 treatment, The values of Fv were 235.86, 221.86 and 147.71, respectively. The values of Fm were 287.57, 275.71 and 201.57, respectively. It increased the antioxidant enzyme activity and reduced the leaf's malondialdehyde (MDA) content to a certain extent. It is concluded that AMF can enhance the photosynthetic capacity of the host, regulate the distribution of endogenous hormones in plants, and promote plant growth by increasing the activity of antioxidant enzymes. When the P supply is insufficient, AMF is more helpful to plants, and R.i is more effective than F.m in alleviating P starvation stress in Chinese fir.

Dietary restriction fails to extend lifespan of Drosophila model of Werner syndrome.

Werner syndrome (WS) is a rare genetic disease in humans, caused by mutations in the WRN gene that encodes a protein containing helicase and exonuclease domains. WS is characterized by symptoms of accelerated aging in multiple tissues and organs, involving increased risk of cancer, heart failure, and metabolic dysfunction. These conditions ultimately lead to the premature mortality of patients with WS. In this study, using the null mutant flies (WRNexoΔ) for the gene WRNexo (CG7670), homologous to the exonuclease domain of WRN in humans, we examined how diets affect the lifespan, stress resistance, and sleep/wake patterns of a Drosophila model of WS. We observed that dietary restriction (DR), one of the most robust nongenetic interventions to extend lifespan in animal models, failed to extend the lifespan of WRNexoΔ mutant flies and even had a detrimental effect in females. Interestingly, the mean lifespan of WRNexoΔ mutant flies was not reduced on a protein-rich diet compared to that of wild-type (WT) flies. Compared to WT control flies, the mutant flies also exhibited altered responses to DR in their resistance to starvation and oxidative stress, as well as changes in sleep/wake patterns. These findings show that the WRN protein is necessary for mediating the effects of DR and suggest that the exonuclease domain of WRN plays an important role in metabolism in addition to its primary role in DNA-repair and genome stability.

Transcriptome analysis revealed changes in multiple genes in Larimichthys crocea under starvation stress

To identify important functional genes of the large yellow croaker (Larimichthys crocea) under starvation stress, the expression changes of genes in muscles tissue of fish fasted for 0, 4, 8, 12, 16, and 20 d were analyzed with RNA-seq technology. Sequencing results showed that a total of 507 million clean reads were generated. Totals of 662, 998, 1015, 1260, and 1122 of differentially expressed genes (DEGs) were obtained at 4, 8, 12, 16, and 20 d, respectively, using starvation 0 d as control. Gene ontology (GO) classification and analysis showed that DEGs could be classified into 42 categories of biological processes, cellular components, and molecular functions. Of these, DEGs are enriched in regulations such as metabolic process, cellular process and single-organism process. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs involved a total of 22 pathways, eight of which were metabolic pathways. With fewer pathways enrichment entry in early starvation stages, but more pathways enrichment entry in late starvation stages (such as at 16 days of starvation), DEGs were significantly enriched in glycolysis/gluconeogenesis, biosynthesis of amino acids, carbon metabolism, fructose and mannose metabolism, methane metabolism and carbon fixation in photosynthetic organisms. After 20 days of starvation, DEGs began to be significantly enriched in the immune pathway, indicating that at this time, fish began to show an immunomodulatory response. This study systematically disclosed the changes of muscle tissue genes in large yellow croaker under starvation stress. The obtained results contribute to research on environmental stress in teleost fish.

Effect of salinity, nitrogen and phosphorus stresses on growth and photosynthetic activity of the marine microalga Dunaliella parva

The growth of the marine green alga Dunaliella parva was studied and optimized under different salinity levels of NaCl (0.5, 1, 2, 2.5, and 3.5 M). The growth was monitored by cell number pigment content (Chl. a, Chl. b, and carotenoids). The grown alga, under the optimal conditions, was exposed to different stresses (nitrogen, phosphorus starvation, and salinity either singly or combined. Under nitrogen and phosphorus starvation, either singly or combined, the growth rate and the metabolic activities were decreased. Under salt stress (2.5 M NaCl) combined with N starvation and heavy metals stress, glycerol production increased, while glycerol synthesis decreased under salt stress of 1 M NaCl and P starvation. Also, free radicals (total antioxidant, reducing power, DPPH, and Lipid peroxidation), pigment content, and activity of antioxidant enzymes were recorded. D. parva grown under salinity level (2.5 M NaCl) combined with nutrient starvation correlated with more efficient enzymatic antioxidant activity accumulation. This study strongly suggested that the induction of antioxidant defense was one component of the tolerance mechanism of D. parva to salinity, as evidenced by its growth behavior.

Nutrient limitation and oxidative stress induce the promoter of acetate operon in Salmonella Typhimurium.

Glyoxylate shunt is an important pathway for microorganisms to survive under multiple stresses. One of its enzymes, malate synthase (encoded by aceB gene), has been widely speculated for its contribution to both the pathogenesis and virulence of various microorganisms. We have previously demonstrated that malate synthase (MS) is required for the growth of Salmonella Typhimurium (S. Typhimurium) under carbon starvation and survival under oxidative stress conditions. The aceB gene is encoded by the acetate operon in S. Typhimurium. We attempted to study the activity of acetate promoter under both the starvation and oxidative stress conditions in a heterologous system. The lac promoter of the pUC19 plasmid was substituted with the putative promoter sequence of the acetate operon of S. Typhimurium upstream to the lacZ gene and transformed the vector construct into E. coli NEBα cells. The transformed cells were subjected to the stress conditions mentioned above. We observed a fourfold increase in the β-galactosidase activity in these cells resulting from the upregulation of the lacZ gene in the stationary phase of cell growth (nutrient deprived) as compared to the mid-log phase. Following exposure of stationary phase cells to hypochlorite-induced oxidative stress, we further observed a 1.6-fold increase in β galactosidase activity. These data suggest the induction of promoter activity of the acetate operon under carbon starvation and oxidative stress conditions. Thus, these observations corroborate our previous findings regarding the upregulation of aceB expression under stressful environments.