Carbohydrate Availability Research Articles

Mucosal sugars delineate pyrazine vs pyrazinone autoinducer signaling in Klebsiella oxytoca

Virulent Klebsiella oxytoca strains are associated with gut and lung pathologies, yet our understanding of the molecular signals governing pathogenesis remains limited. Here, we characterized a family of K. oxytoca pyrazine and pyrazinone autoinducers and explored their roles in microbial and host signaling. We identified the human mucin capping sugar Neu5Ac as a selective elicitor of leupeptin, a protease inhibitor prevalent in clinical lung isolates of K. oxytoca, and leupeptin-derived pyrazinone biosynthesis. Additionally, we uncovered a separate pyrazine pathway, regulated by general carbohydrate metabolism, derived from a broadly conserved PLP-dependent enzyme. While both pyrazine and pyrazinone signaling induce iron acquisition responses, including enterobactin biosynthesis, pyrazinone signaling enhances yersiniabactin virulence factor production and selectively activates the proinflammatory human histamine receptor H4 (HRH4). Our findings suggest that the availability of specific carbohydrates delineates distinct autoinducer pathways in K. oxytoca that may have differential effects on bacterial virulence and host immune responses.

Brown fat ATP-citrate lyase links carbohydrate availability to thermogenesis and guards against metabolic stress.

Brown adipose tissue (BAT) engages futile fatty acid synthesis-oxidation cycling, the purpose of which has remained elusive. Here, we show that ATP-citrate lyase (ACLY), which generates acetyl-CoA for fatty acid synthesis, promotes thermogenesis by mitigating metabolic stress. Without ACLY, BAT overloads the tricarboxylic acid cycle, activates the integrated stress response (ISR) and suppresses thermogenesis. ACLY's role in preventing BAT stress becomes critical when mice are weaned onto a carbohydrate-plentiful diet, while removing dietary carbohydrates prevents stress induction in ACLY-deficient BAT. ACLY loss also upregulates fatty acid synthase (Fasn); yet while ISR activation is not caused by impaired fatty acid synthesis per se, deleting Fasn and Acly unlocks an alternative metabolic programme that overcomes tricarboxylic acid cycle overload, prevents ISR activation and rescues thermogenesis. Overall, we uncover a previously unappreciated role for ACLY in mitigating mitochondrial stress that links dietary carbohydrates to uncoupling protein 1-dependent thermogenesis and provides fundamental insight into the fatty acid synthesis-oxidation paradox in BAT.

Examination Of Energy Availability, Eating Disorders And Carbohydrate Availability Among College-age Runners

Examination Of Energy Availability, Eating Disorders And Carbohydrate Availability Among College-age Runners

Examination Of Energy Availability, Eating Disorder Risk, Carbohydrate Availability Among Collegiate Rotc Cadets

Examination Of Energy Availability, Eating Disorder Risk, Carbohydrate Availability Among Collegiate Rotc Cadets

Responses to Exercise with Low Carbohydrate Availability on Muscle Glycogen and Cell Signaling: A Systematic Review and Meta-analysis.

The growing interest in how exercise and carbohydrate (CHO) restriction may modify molecular responses that promote endurance adaptations has led to many interesting controversies. We conducted a systematic review and a meta-analysis regarding the effect of low-carbohydrate availability (LOW) pre-, during, or post-exercise, on the mRNA content of commonly measured genes involved in mitochondrial biogenesis (PGC-1α, TFAM mRNA) and metabolism (PDK4, UCP3 and GLUT4 mRNA), and on muscle glycogen levels, compared with a high-CHO (CON) condition. MEDLINE, Scopus, and Web of Science databases were searched following the PRISMA 2020 guidelines (with an end date of November 2023). In total, 19 randomized-controlled studies were considered for inclusion. We evaluated the methodological quality of all studies using the Cochrane Risk of Bias tool for randomized clinical studies. A meta-analysis was performed using a random effects model to calculate the standardized mean difference (SMD), estimated by Hedges' g, and 95% confidence intervals (CIs). The LOW condition was associated with an increased mRNA content of several genes during the early recovery period post-exercise, such as PDK4 (SMD 1.61; 95% CI 0.80-2.42), GLUT4 (SMD 1.38; 95% CI 0.46-2.30), and UCP3 (SMD 2.05; 95% CI 0.40-3.69). However, overall, there was no significant effect on the mRNA content of PGC-1α or TFAM. Finally, CHO restriction and exercise significantly reduced muscle glycogen levels (SMD 3.69; 95% CI 2.82-5.09). A meta-analysis of subgroups from studies with a difference in muscle glycogen concentration of > 200mmolkgdw-1 between the LOW and CON conditions showed an increase in exercise-induced PGC-1α mRNA (SMD 2.08; 95% CI 0.64-3.52; p = 0.005; I2 = 75%) and a greater effect in PDK4 and GLUT4 mRNA. The meta-analysis results show that CHO restriction was associated with an increase in the exercise-induced mRNA content of PDK4, UCP3, and GLUT4, but not the exercise-induced mRNA content of PGC-1ɑ and TFAM. However, when there were substantial differences in glycogen depletion between CON and LOW CHO conditions (> 200mmolkgdw-1), there was a greater effect of CHO restriction on the exercise-induced mRNA content of metabolic genes, and an increase in exercise-induced PGC-1α mRNA.

Training with reduced carbohydrate availability affects markers of bone resorption and formation in male academy soccer players from the English Premier League.

To test the hypothesis that training with reduced carbohydrate (CHO) availability increases bone resorption in adolescent soccer players. In a randomised crossover design, ten male players (age: 17.4 ± 0.8years) from an English Premier League academy completed an acute 90-min field-based training session (occurring between 10:30-12:00) in conditions of high (TRAIN HIGH; 1.5g.kg-1, 60g, 1.5g.kg-1 and 1.5g.kg-1 consumed at 08:00, during training, 12:30 and 13:30, respectively) or low CHO availability (TRAIN LOW; 0g.kg-1). Participants also completed a non-exercise trial (REST) under identical dietary conditions to TRAIN LOW. Venous blood samples were obtained at 08:30, 10:30, 12:30 and 14:30 for assessment of bone resorption (βCTX), bone formation (PINP) and calcium metabolism (PTH and ACa). External training load did not differ (all P > 0.05) between TRAIN HIGH and TRAIN LOW, as evident for total distance (5.6 ± 0.8; 5.5 ± 0.1km), average speed (81 ± 9; 85 ± 12m.min-1) and high-speed running (350 ± 239; 270 ± 89m). Area under the curve for both βCTX and PINP was significantly greater (P < 0.01 and P = 0.03) in TRAIN LOW versus TRAIN HIGH, whilst no differences in PTH or ACa (P = 0.11 and P = 0.89) were observed between all three trials. CHO restriction before, during and after an acute soccer training session increased bone (re)modelling markers in academy players. Despite acute anabolic effects of bone formation, the long-term consequence of bone resorption may impair skeletal development and increase injury risk during growth and maturation.

The Influence of Nutrition Intervention on the P1NP and CTX-1 Response to an Acute Exercise Bout: A Systematic Review with Meta-Analysis.

Although nutrition and exercise both influence bone metabolism, little is currently known abouttheir interaction, or whether nutritional intervention can modulate the bone biomarker response to acute exercise. Improved understanding of the relationships between nutrition, exercise and bone metabolism may have substantial potential to inform nutritional interventions to protect the bone health of exercising individuals, and to elucidate mechanisms by which exercise and nutrition influence bone. The aim was to synthesise available evidence related to the influence of nutrition on the response of the bone biomarkers procollagen type 1 N-terminal propeptide (P1NP) and C-terminal telopeptide of type 1 collagen (CTX-1) to acute exercise, using a systematic review and meta-analytic approach. Studies evaluating the influence of nutritional status or intervention on the bone biomarker response to an acute exercise bout were included and separated into four categories: (1) feeding status and energy availability, (2) macronutrients, (3) micronutrients and (4) other. Studies conducted on healthy human populations of any age or training status were included. Meta-analysis was conducted when data from at least five studies with independent datasets were available. In the case of insufficient data to warrant meta-analysis, results from individual studies were narratively synthesised and standardised mean effect sizes visually represented. Twenty-two articles were included. Of these, three investigated feeding status or energy availability, eight macronutrients, eight micronutrients (all calcium) and six other interventions including dairy products or collagen supplementation. Three studies had more than one intervention and were included in all relevant outcomes. The largest and most commonly reported effects were for the bone resorption marker CTX-1. Meta-analysis indicated that calcium intake, whether provided via supplements, diet or infusion, reduced exercise-induced increases in CTX-1 (effect size - 1.1; 95% credible interval [CrI] - 2.2 to - 0.05), with substantially larger effects observed in studies that delivered calcium via direct infusion versus in supplements or foods. Narrative synthesis suggests that carbohydrate supplementation may support bone during acute exercise, via reducing exercise-induced increases in CTX-1. Conversely, a low-carbohydrate/high-fat diet appears to induce the opposite effect, as evidenced by an increased exercise associated CTX-1 response, and reduced P1NP response. Low energy availability may amplify the CTX-1 response to exercise, but it is unclear whether this is directly attributable to energy availability or to the lack of specific nutrients, such as carbohydrate. Nutritional intervention can modulate the acute bone biomarker response to exercise, which primarily manifests as an increase in bone resorption. Ensuring adequate attention to nutritional factors may be important to protect bone health of exercising individuals, with energy, carbohydrate and calcium availability particularly important to consider. Although a wide breadth of data were availablefor this evidence synthesis, there was substantial heterogeneity in relation to design and intervention characteristics. Direct and indirect replication is required to confirm key findings and to generate better estimates of true effect sizes.

Increased resting lactate levels and reduced carbohydrate intake cause νLa.max underestimation by reducing net lactate accumulation-A pilot study in young adults.

Modulation of testing conditions such as resting lactate (Larest) levels or carbohydrate intake may affect the calculation of the maximal glycolytic rate (νLa.max). To evaluate the impact of elevated Larest as well as reduced and increased carbohydrate availability on νLa.max in running sprints (RST), twenty-one participants completed five 15-s RST tests on a running track under five different conditions: (I). baseline: Larest ≤1.5 mmol·L-1; (II). Lactate+: Larest ≥2.5 mmol·L-1; (III). CHO-: carbohydrate intake: ≤ 1 g·kg-1 BW d-1 for 3 days; (IV). CHO+: carbohydrate intake: ≥ 9 g·kg-1 BW d-1 for one day; and (V). acuteCHO: 500 mL glucose containing beverage consumed before RST. νLa.max was significantly reduced in lactate+ and CHO- conditions compared to the baseline RST, due to a reduction in the arithmetic mean delta (∆) between Lapeak and Larest lactate concentration (Lapeak, mmol · L-1). AcuteCHO led to an increase in Larest compared to baseline, CHO- and CHO+ with a high interindividual variability but did not significantly reduce νLa.max. Therefore, avoiding low carbohydrate nutrition before νLa.max testing, along with carefully adjusting Larest to below ≤1.5 mmol·L-1, is crucial to prevent the unintentional underestimation of νLa.max.

In Vitro Fermentation of Animal and Plant Protein Isolates by the Human Gut Microbiota Under High and Low Carbohydrate Conditions.

There is a lack of research comparing how different protein isolates influence the microbiome, especially when carbohydrate (CHO) availability is varied. The objective is to determine changes in gut microbiota composition and function during fermentation of digested protein isolates under high and low CHO conditions. Protein isolates from beef, egg white, milk, pea, and soy are subjected to in vitro digestion and fermentation with human fecal microbiota. Under low CHO conditions, the microbiota is primarily proteolytic with decreased concentrations of peptides and increased variance among microbial taxa and production of ammonia and branched chain fatty acids by the microbiota. Milk protein not only results in the highest production of butyrate and p-hydroxyphenylacetate but also has high concentrations of deleterious fermentation metabolites. Amino acid composition of the protein isolates is significantly correlated with abundances of many microbial taxa and metabolites, but the correlations are stronger in the low CHO medium. This study shows that low CHO conditions increase proteolytic fermentation and result in increased differences in microbiota response to protein isolates. It also showed that amino acid composition is highly associated with microbiota composition and function especially under low CHO conditions.

Effect of a high carbohydrate pre-exercise meal on metabolic and performance-related parameters in male athletes following two different strategies to improve fat utilization: An exploratory examination

The purpose of this additional examination of a larger intervention was to determine the effects of a carbohydrate-rich pre-exercise meal on metabolic and performance-related parameters in a group of male endurance athletes, who had previously followed either a high fat low carbohydrate (HFLC; n = 6) or high carbohydrate low glycaemic (LGI; n = 6) diet for 4 weeks. Participants continued their regular training routine during the intervention. Respiratory exchange ratio (RER), lactate concentrations ([La−]), substrate oxidation rates at rest and during a cycle ergometry with incremental workload were determined in the fasted state and 2 h after consuming a carbohydrate-rich (2 g per kg of body mass) pre-exercise meal. Power output at lactate thresholds, peak oxygen uptake (V̇O2peak), absolute and relative peak power during the incremental test were assessed. After consuming the pre-exercise meal, both groups showed increased levels of RER, [La−] and carbohydrate oxidation at rest and during the incremental test (p < 0.05; Cohen’s d > 0.8), and an improved V̇O2peak (p < 0.05; Cohen’s d > 0.5). Rm ANOVA revealed significant group differences in metabolic parameters. Despite meaningful baseline differences ([La−]: p = 0.133; ηp2 = 0.185; RER: p = 0.037; ηp2 = 0.367; carbohydrate oxidation: p = 0.041; ηp2 = 0.355) upregulation of carbohydrate metabolism was more pronounced in the LGI subgroup compared to the HFLC group after 4-weeks intervention, in both fasted ([La−]: p = 0.130; ηp2 = 0.214; RER: p = 0.001; ηp2 = 0.713; carbohydrate oxidation: p = 0.001; ηp2 =0.684) and postprandial states ([La−]: p = 0.036; ηp2 =0.369; RER: p = 0.001; ηp2 =0.705; carbohydrate oxidation: p = 0.001; ηp2 =0.665). Peak power during the final incremental test was slightly higher in the LGI subgroup compared with the HFLC subgroup (p = 0.320; ηp2 = 0.100). In this group of male endurance athletes, a LGI diet seemed to result in more favourable performance metrics as compared to a HFLC diet despite increases in carbohydrate availability before undertaking the performance test likely due to the ability to sustain higher workloads in training.

Microbiological survey and physicochemical analysis of Moroccan durum, soft and red wheat landraces

Morocco possesses a significant genetic diversity of wheat cultivars in the form of landraces conserved by local farmers in several regions. This study aimed to evaluate the microbiological quality of refined flour and bran derived from 75 samples of Moroccan durum, soft, and red wheat landraces and to estimate their microbiological stability for controlling and preventing undesirable microbial proliferation. Various microbial and physicochemical parameters were evaluated according to ISO and AOAC standards, and results were interpreted based on Codex Alimentarius Commission regulation. Compliance of the analyzed refined flour and bran samples with current regulatory limits and satisfactory microbiological quality were observed. The phenotypic characterization revealed the identification of 16 yeast species belonging to the genera Trichosporon, Candida, Cryptococcus, Rhodotorula, and Saccharomyces, which had not been previously explored. Furthermore, the biodiversity of lactic acid bacteria is notably characterized by the predominance of Pediococcus acidilactici and Lactobacillus plantarum species. The analysis of moisture content and water activity exhibited values falling below the maximum limits defined by international standards, demonstrating the effectiveness of the implemented processing and storage practices. The neutral pH recorded confirms the absence of excessive proliferation of the assessed microbial contaminants. The abundant availability of carbohydrates, lipids, proteins, and minerals creates a favorable non-competitive environment essential for maintaining their functional stability in the analyzed samples. These findings hold significant implications for the agricultural and food industries, providing insights into preserving indigenous wheat varieties and producing safe wheat-based products with high nutritional quality.

Analysis of Supply and Adequacy of Food Based on Food Balance Sheets (Case Study in Purworejo Regency)

One of the factors that cause poverty is the inadequacy of calories from food. The purpose of this study was to find out how much the availability of food ingredients in Purworejo Regency was to meet the needs of the community and to provide an overview of the existing food availability situation. This study used a survey involving 180 respondents from wholesalers in 16 sub-districts in Purworejo Regency, as well as secondary data from related offices/agencies. The method used is a calculation using the Foodstuff Balance which consists of 11 food groups, the level of public consumption of these food groups, to the availability of carbohydrate, protein and fat energy per capita. The results of the analysis obtained: (1) The availability of carbohydrates in Purworejo Regency is 2,619 kcal/cap/day, (2) The availability of Protein is 71.60 grams/cap/day and (3) The availability of Fat is 43.54 grams/day cap/day. Overall the availability of calories and protein in Purworejo has met national standards according to WNPG XI 2018, which is set at 2400 kcal/cap/day, so that the sufficiency of food availability in Purworejo Regency is more than sufficient to meet the needs of its people.

UV-C Treatment Impact on the Availability of Water-Soluble Carbohydrates, Polyphenols, and Antioxidant Capacity of an Algerian Underutilized Date Fruit (Phoenix dactylifera L.).

Underutilized dates are considered as a socioeconomically important fruit for local and global communities, such as Degla-Beida, a common date fruit variety. The aim of this research was to elucidate, for the first time, the efficiency of UV-C light treatment (over different irradiation durations 5, 10, 20, and 40 min) in the enhancement of soluble carbohydrates and phenolic compounds, and to evaluate its effect on the antioxidant capacity. Furthermore, the content of dietary fiber was analyzed: insoluble dietary fiber (11.89 g/100 g); soluble dietary fiber (5.15 g/100 g); and total dietary fiber (17.06 g/100 g). The techno-functional properties were also determined: swelling capacity (3.94 mL/g); oil holding capacity (7.38 g/g); water holding capacity (9.30 g/g); and bulk density (1.81 g/mL). All were carried out to study the potential of exploiting this underutilized fruit for other applications as for feed or food. The results suggest that UV-C technology changes minimally the total water-soluble carbohydrate content; however, this preservation technology can affect the availability of different soluble carbohydrates depending on the irradiation time (IT), increasing the high molecular weight polysaccharides with IT up to 20 min, and some oligosaccharides with IT up to 5 min. The polyphenolic content determined by HPLC-QTOF was increased when the samples were submitted to UV-C reaching the maximum at 20 min (111.62 mg/100 g) and then to decrease in those submitted to IT of 40 min (12.05 mg/100 g). Regarding antioxidant capacity in the UV-C treated samples, FRAP decreased and EC50 on DPPH increased when IT was increased, while ORAC was hardly maintained. In addition, considering UV-C radiation associated with preservation and the studied date fruit as a rich source of dietary fiber with adequate techno-functional properties, this study presents valuable information for its potential use as a new food ingredient.

Assessing the effect of artificial shading and saccharose sprays on the yield and fruit quality of cranberry (Vaccinium macrocarpon Aiton)

ABSTRACT A natural low fruit set is reported in cranberry. It is hypothesised that a carbohydrate shortage limits fruit set, and thus yield potential. We aimed to evaluate the effect of carbohydrate availability induced by shade and saccharose spraying during reproductive stages of ‘Stevens’ cranberry to identify critical periods for yield and juice quality (soluble solids, acidity, and colour). Two independent experiments were conducted. On five separate dates, artificial shade (90% shade nets) was imposed for two weeks. On the same dates, 417 kg ha−1 of saccharose was sprayed as a 10% w/v solution. Results showed that shading from full bloom to the beginning of the fruit set reduced fruit number and juice colour. In contrast, 10% saccharose spray increased yield by 22% compared to the control without compromising juice quality. Therefore, the period between the end of full bloom and the beginning of fruit growth is the most critical stage for ‘Stevens’ cranberry.

Effect of PEF Treatment on Chosen Properties of Raw and Hot Air- and Freeze-Dried Poultry Meat

The properties of fresh meat, such as high water activity, a slightly acidic reaction, and the availability of carbohydrates and proteins, make it a microbiologically unstable and easily perishable raw material. One of the oldest food preservation techniques is drying. Furthermore, non-thermal food processing techniques such as pulse electric field (PEF) treatment can be used to support the drying process and change the properties of the obtained product. Thus, this study aimed to analyze the impact of pulsed electric field treatment on the hot air-drying and freeze-drying of poultry meat as well as on the quality of the dried meat. The PEF pretreatment and drying methods significantly altered the physical characteristics of the poultry meat. The PEF treatment enhanced the efficiency of freeze-drying by electroporation, reducing drying time and shrinkage. However, in the hot air-drying, the PEF-treated samples prolonged drying, potentially due to muscle structure damage and increased shrinkage. The pretreatment techniques affected the structure of the meat and positively influenced the higher porosity and lower shrinkage. Also, drying decreased the water activity and increased the dry matter content, which ensured the safety of the final product. The freeze-dried material exhibited a higher rehydration rate, improved hygroscopic properties, and better meat color compared to the hot air-dried material. Nevertheless, the selection of the process parameters, for both the pretreatment and drying process, is crucial to ensure a high quality of the dried meat product and should be selected carefully in order to guarantee that the highest quality of the dried product is obtained.

A Five-Week Periodized Carbohydrate Diet Does Not Improve Maximal Lactate Steady-State Exercise Capacity and Substrate Oxidation in Well-Trained Cyclists compared to a High-Carbohydrate Diet.

There is a growing interest in studies involving carbohydrate (CHO) manipulation and subsequent adaptations to endurance training. This study aimed to analyze whether a periodized carbohydrate feeding strategy based on a daily training session has any advantages compared to a high-carbohydrate diet in well-trained cyclists. Seventeen trained cyclists (VO2peak = 70.8 ± 6.5 mL·kg-1·min-1) were divided into two groups, a periodized (PCHO) group and a high-carbohydrate (HCHO) group. Both groups performed the same training sessions for five weeks. In the PCHO group, 13 training sessions were performed with low carbohydrate availability. In the HCHO group, all sessions were completed following previous carbohydrate intake to ensure high pre-exercise glycogen levels. In both groups, there was an increase in the maximal lactate steady state (MLSS) (PCHO: 244.1 ± 29.9 W to 253.2 ± 28.4 W; p = 0.008; HCHO: 235.8 ± 21.4 W to 246.9 ± 16.7 W; p = 0.012) but not in the time to exhaustion at MLSS intensity. Both groups increased the percentage of muscle mass (PCHO: p = 0.021; HCHO: p = 0.042) and decreased the percent body fat (PCHO: p = 0.021; HCHO: p = 0.012). We found no differences in carbohydrate or lipid oxidation, heart rate, and post-exercise lactate concentration. Periodizing the CHO intake in well-trained cyclists during a 5-week intervention did not elicit superior results to an energy intake-matched high-carbohydrate diet in any of the measured outcomes.

Blood glucose control in acute stroke patients under total energy restriction with different carbohydrate intake and SGLT2 inhibitors availability: a retrospective cohort study

Hyperglycemia in acute stroke patients worsens neurological outcomes. However, effective and safe management during the acute stage has not been established. Therefore, we aimed to compare the effect of medications and nutrition therapy on blood glucose control in three cohorts with different carbohydrate content and availability of sodium-glucose cotransporter 2 inhibitors (SGLT2is) to identify the current optimal treatment for acute-stage hyperglycemia. We retrospectively studied patients with acute stroke admitted to our hospital between 2011 and 2019. We divided the study period into three periods as follows: traditional (Td, 2011–2013), transition (Ts, 2013–2014), and novel (N, 2014–2019). To evaluate glucose-lowering efficacy and safety, we included conscious patients with glycated hemoglobin A1c ≥6.5%, blood glucose levels ≥11.1 mmol/L, normal renal function at admission, oral diet and medications, and fasting blood glucose (FBG) test on day 7. We performed total energy restriction (TER) in each period with different carbohydrate contents: 60% in Td, 40% in Ts, and N. The attending physicians chose glucose-lowering medications. SGLT2is were available in the N period only. Our target FBG was &lt;7 mmol/L by day 7. The 26, 22 and 36 patients were enrolled in the Td, Ts and N periods. The blood glucose levels significantly decreased by day 7 in all periods. The target FBG was achieved in 30.8% of Td patients, 31.8% of Ts patients, and 72.2% of N patients. The N period had the highest population of achieving the target FBG. The 40%-carbohydrate diet based on TER plus SGLT2is was the most effective way to lower blood glucose levels. The N period had the highest population of positive urine ketones. However, no symptomatic ketoacidosis occurred. A 40%-carbohydrate diet based on TER combined with SGLT2is might be a potentially effective and safe treatment for hyperglycemia in acute stroke-conscious patients.

Ethylene inhibits photosynthesis via temporally distinct responses in tomato plants.

Ethylene is a volatile plant hormone that regulates many developmental processes and responses toward (a)biotic stress. Studies have shown that high levels of ethylene repress vegetative growth in many important crops, including tomato (Solanum lycopersicum), possibly by inhibiting photosynthesis. We investigated the temporal effects of ethylene on young tomato plants using an automated ethylene gassing system to monitor the physiological, biochemical, and molecular responses through time course RNA-seq of a photosynthetically active source leaf. We found that ethylene evokes a dose-dependent inhibition of photosynthesis, which can be characterized by 3 temporally distinct phases. The earliest ethylene responses that marked the first phase and occurred a few hours after the start of the treatment were leaf epinasty and a decline in stomatal conductance, which led to lower light perception and CO2 uptake, respectively, resulting in a rapid decline of soluble sugar levels (glucose, fructose). The second phase of the ethylene effect was marked by low carbohydrate availability, which modulated plant energy metabolism to adapt by using alternative substrates (lipids and proteins) to fuel the TCA cycle. Long-term continuous exposure to ethylene led to the third phase, characterized by starch and chlorophyll breakdown, which further inhibited photosynthesis, leading to premature leaf senescence. To reveal early (3 h) ethylene-dependent regulators of photosynthesis, we performed a ChIP-seq experiment using anti-ETHYLENE INSENSITIVE 3-like 1 (EIL1) antibodies and found several candidate transcriptional regulators. Collectively, our study revealed a temporal sequence of events that led to the inhibition of photosynthesis by ethylene and identified potential transcriptional regulators responsible for this regulation.

Nonstructural carbohydrates explain post-fire tree mortality and recovery patterns.

Trees use nonstructural carbohydrates (NSCs) to support many functions, including recovery from disturbances. However, NSC's importance for recovery following fire and whether NSC depletion contributes to post-fire delayed mortality are largely unknown. We investigated how fire affects NSCs based on fire-caused injury from a prescribed fire in a young Pinus ponderosa (Lawson & C. Lawson) stand. We assessed crown injury (needle scorch and bud kill) and measured NSCs of needles and inner bark (i.e., secondary phloem) of branches and main stems of trees subject to fire and at an adjacent unburned site. We measured NSCs pre-fire and at six timesteps post-fire (4days-16months). While all trees initially survived the fire, NSC concentrations declined quickly in burned trees relative to unburned controls over the same post-fire period. This decline was strongest for trees that eventually died, but those that survived recovered to unburned levels within 14months post-fire. Two months post-fire, the relationship between crown scorch and NSCs of the main stem inner bark was strongly negative (Adj-R2=0.83). Our results support the importance of NSCs for tree survival and recovery post-fire and suggest that post-fire NSC depletion is in part related to reduced photosynthetic leaf area that subsequently limits carbohydrate availability for maintaining tree function. Crown scorch is a commonly measured metric of tree-level fire severity and is often linked to post-fire tree outcome (i.e., recovery or mortality). Thus, our finding that NSC depletion may be the mechanistic link between the fire-caused injury and tree outcome will help improve models of post-fire tree mortality and forest recovery.

Purine and carbohydrate availability drive Enterococcus faecalis fitness during wound and urinary tract infections.

Although E. faecalis is a common wound pathogen, its pathogenic mechanisms during wound infection are unexplored. Here, combining a mouse wound infection model with in vivo transposon and RNA sequencing approaches, we identified the E. faecalis purine biosynthetic pathway and galactose/mannose MptABCD phosphotransferase system as essential for E. faecalis acute replication and persistence during wound infection, respectively. The essentiality of purine biosynthesis and the MptABCD PTS is driven by the consumption of purine metabolites by E. faecalis during acute replication and changing carbohydrate availability during the course of wound infection. Overall, our findings reveal the importance of the wound microenvironment in E. faecalis wound pathogenesis and how these metabolic pathways can be targeted to better control wound infections.