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1.
AFB1 controls rapid auxin signalling through membrane depolarization in Arabidopsis thaliana root.
Serre, NBC, Kralík, D, Yun, P, Slouka, Z, Shabala, S, Fendrych, M
Nature plants. 2021;(9):1229-1238
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Abstract
The membrane potential reflects the difference between cytoplasmic and apoplastic electrical potentials and is essential for cellular operation. The application of the phytohormone auxin (3-indoleacetic acid (IAA)) causes instantaneous membrane depolarization in various cell types1-6, making depolarization a hallmark of IAA-induced rapid responses. In root hairs, depolarization requires functional IAA transport and TIR1-AFB signalling5, but its physiological importance is not understood. Specifically in roots, auxin triggers rapid growth inhibition7-9 (RGI), a process required for gravitropic bending. RGI is initiated by the TIR1-AFB co-receptors, with the AFB1 paralogue playing a crucial role10,11. The nature of the underlying rapid signalling is unknown, as well as the molecular machinery executing it. Even though the growth and depolarization responses to auxin show remarkable similarities, the importance of membrane depolarization for root growth inhibition and gravitropism is unclear. Here, by combining the DISBAC2(3) voltage sensor with microfluidics and vertical-stage microscopy, we show that rapid auxin-induced membrane depolarization tightly correlates with RGI. Rapid depolarization and RGI require the AFB1 auxin co-receptor. Finally, AFB1 is essential for the rapid formation of the membrane depolarization gradient across the gravistimulated root. These results clarify the role of AFB1 as the central receptor for rapid auxin responses.
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Acute Beetroot Juice Supplementation Does Not Improve Cycling Performance in Normoxia or Moderate Hypoxia.
MacLeod, KE, Nugent, SF, Barr, SI, Koehle, MS, Sporer, BC, MacInnis, MJ
International journal of sport nutrition and exercise metabolism. 2015;(4):359-66
Abstract
Beetroot juice (BR) has been shown to lower the oxygen cost of exercise in normoxia and may have similar effects in hypoxia. We investigated the effect of BR on steady-state exercise economy and 10-km time trial (TT) performance in normoxia and moderate hypoxia (simulated altitude: ~2500 m). Eleven trained male cyclists (VO 2peak ≥ 60 ml · kg(-1) · min(-1)) completed four exercise trials. Two hours before exercise, subjects consumed 70 mL BR (~6 mmol nitrate) or placebo (nitrate-depleted BR) in a randomized, double-blind manner. Subjects then completed a 15-min self-selected cycling warm-up, a 15-min steady-state exercise bout at 50% maximum power output, and a 10-km time trial (TT) in either normoxia or hypoxia. Environmental conditions were randomized and single-blind. BR supplementation increased plasma nitrate concentration and fraction of exhaled nitric oxide relative to PL (p < .05 for both comparisons). Economy at 50% power output was similar in hypoxic and normoxic conditions (p > .05), but mean power output was greater in the normoxic TT relative to the hypoxic TT (p < .05). BR did not affect economy, steady-state SpO2, mean power output, or 10-km TT completion time relative to placebo in either normoxia or hypoxia (p > .05 in all comparisons). In conclusion, BR did not lower the oxygen cost of steady-state exercise or improve exercise performance in normoxia or hypoxia in a small sample of well-trained male cyclists.
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3.
Carotenoids are more bioavailable from papaya than from tomato and carrot in humans: a randomised cross-over study.
Schweiggert, RM, Kopec, RE, Villalobos-Gutierrez, MG, Högel, J, Quesada, S, Esquivel, P, Schwartz, SJ, Carle, R
The British journal of nutrition. 2014;(3):490-8
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Abstract
Carrot, tomato and papaya represent important dietary sources of β-carotene and lycopene. The main objective of the present study was to compare the bioavailability of carotenoids from these food sources in healthy human subjects. A total of sixteen participants were recruited for a randomised cross-over study. Test meals containing raw carrots, tomatoes and papayas were adjusted to deliver an equal amount of β-carotene and lycopene. For the evaluation of bioavailability, TAG-rich lipoprotein (TRL) fractions containing newly absorbed carotenoids were analysed over 9·5 h after test meal consumption. The bioavailability of β-carotene from papayas was approximately three times higher than that from carrots and tomatoes, whereas differences in the bioavailability of β-carotene from carrots and tomatoes were insignificant. Retinyl esters appeared in the TRL fractions at a significantly higher concentration after the consumption of the papaya test meal. Similarly, lycopene was approximately 2·6 times more bioavailable from papayas than from tomatoes. Furthermore, the bioavailability of β-cryptoxanthin from papayas was shown to be 2·9 and 2·3 times higher than that of the other papaya carotenoids β-carotene and lycopene, respectively. The morphology of chromoplasts and the physical deposition form of carotenoids were hypothesised to play a major role in the differences observed in the bioavailability of carotenoids from the foods investigated. Particularly, the liquid-crystalline deposition of β-carotene and the storage of lycopene in very small crystalloids in papayas were found to be associated with their high bioavailability. In conclusion, papaya was shown to provide highly bioavailable β-carotene, β-cryptoxanthin and lycopene and may represent a readily available dietary source of provitamin A for reducing the incidence of vitamin A deficiencies in many subtropical and tropical developing countries.
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Aged garlic extract reduces blood pressure in hypertensives: a dose-response trial.
Ried, K, Frank, OR, Stocks, NP
European journal of clinical nutrition. 2013;(1):64-70
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Abstract
BACKGROUND/OBJECTIVES Hypertension affects about 30% of adults worldwide. Garlic has blood pressure-lowering properties and the mechanism of action is biologically plausible. Our trial assessed the effect, dose-response, tolerability and acceptability of different doses of aged garlic extract as an adjunct treatment to existing antihypertensive medication in patients with uncontrolled hypertension. SUBJECTS/METHODS A total of 79 general practice patients with uncontrolled systolic hypertension participated in a double-blind randomised placebo-controlled dose-response trial of 12 weeks. Participants were allocated to one of three garlic groups with either of one, two or four capsules daily of aged garlic extract (240/480/960 mg containing 0.6/1.2/2.4 mg of S-allylcysteine) or placebo. Blood pressure was assessed at 4, 8 and 12 weeks and compared with baseline using a mixed-model approach. Tolerability was monitored throughout the trial and acceptability was assessed at 12 weeks by questionnaire. RESULTS Mean systolic blood pressure was significantly reduced by 11.8±5.4 mm Hg in the garlic-2-capsule group over 12 weeks compared with placebo (P=0.006), and reached borderline significant reduction in the garlic-4-capsule group at 8 weeks (-7.4±4.1 mm Hg, P=0.07). Changes in systolic blood pressure in the garlic-1-capsule group and diastolic blood pressure were not significantly different to placebo. Tolerability, compliance and acceptability were high in all garlic groups (93%) and highest in the groups taking one or two capsules daily. CONCLUSIONS Our trial suggests aged garlic extract to be an effective and tolerable treatment in uncontrolled hypertension, and may be considered as a safe adjunct treatment to conventional antihypertensive therapy.
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Blood pressure-lowering effects of beetroot juice and novel beetroot-enriched bread products in normotensive male subjects.
Hobbs, DA, Kaffa, N, George, TW, Methven, L, Lovegrove, JA
The British journal of nutrition. 2012;(11):2066-74
Abstract
A number of vegetables have a high nitrate content which after ingestion can be reduced to nitrite by oral bacteria, and further to vasoprotective NO endogenously. In the present study, two separate randomly controlled, single-blind, cross-over, postprandial studies were performed in normotensive volunteers. Ambulatory blood pressure (BP) was measured over a 24 h period following consumption of either four doses of beetroot juice (BJ), 0, 100, 250 and 500 g (n 18), or three bread products, control bread (0 g beetroot), red beetroot- and white beetroot-enriched breads (n 14). Total urinary nitrate/nitrite (NO(x)) was measured at baseline, and at 2, 4 and 24 h post-ingestion. BJ consumption significantly, and in a near dose-dependent manner, lowered systolic BP (SBP, P < 0·01) and diastolic BP (DBP, P < 0·001) over a period of 24 h, compared with water control. Furthermore, bread products enriched with 100 g red or white beetroot lowered SBP and DBP over a period of 24 h (red beetroot-enriched bread, P <0·05), with no statistical differences between the varieties. Total urinary NO(x) significantly increased following the consumption of 100 g (P < 0·01), 250 g (P <0·001) and 500 g BJ (P <0·001) and after red beetroot-enriched bread ingestion (P <0·05), but did not reach significance for white beetroot-enriched bread compared with the no-beetroot condition. These studies demonstrated significant hypotensive effects of a low dose (100 g) of beetroot which was unaffected by processing or the presence of betacyanins. These data strengthen the evidence for cardioprotective BP-lowering effects of dietary nitrate-rich vegetables.
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Application of plant-based antimicrobials for the growth inhibition of clostridia in pressed beet pulp silage.
Emerstorfer, F, Hein, W, Resch, R, Poetsch, EM, Zitz, U, Kneifel, W
Journal of the science of food and agriculture. 2011;(11):2038-44
Abstract
BACKGROUND In this study the inhibition of hop beta acids on the growth of clostridia in soil-contaminated pressed sugar beet pulp silages was investigated. Hop beta acids are natural substances which display their effect at low concentrations. Fresh pressed beet pulp material was mixed with soil to artificially contaminate it with clostridia. Laboratory silos were filled with the substrate, stored at 25 °C and opened for sampling at 0, 2, 8, 15, 30, 60, and 90 days. The impact on clostridial growth during silage fermentation was monitored by determination of the pH value and dry matter content, as well as chemical analysis of the fermentation products. Throughout the experiments, the effect of a commercial silage inoculant based on lactic acid bacteria (LAB) and hop-resistant LAB were examined with and without the combination of plant-based antimicrobials. RESULTS Results indicate that in contaminated silage samples without any additives high butyric acid contents occurred due to clostridial growth. This spoilage could not be suppressed by the application of LAB, whereas the combined application of LAB and hop beta acids significantly improved silage quality, which was reflected by favourable organic acid composition (P < 0.05). CONCLUSION The experimental data indicate that the application of hop beta acids improves the preservation effect of LAB in suppressing clostridial growth in silages and thus demonstrates some potential for the combined use of plant-based antimicrobials and LAB.
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HPLC analysis of oleuropein, hydroxytyrosol, and tyrosol in stems and roots of Olea europaea L. cv. Picual during ripening.
Ortega-García, F, Peragón, J
Journal of the science of food and agriculture. 2010;(13):2295-300
Abstract
BACKGROUND Oleuropein (Ole), hydroxytyrosol (Htyr), and tyrosol (Tyr) are three of the main phenolic compounds present in the olive tree (Olea europaea L.) that have important antioxidant properties. To investigate the role of these phenolic compounds in the metabolism of stems and roots of Olea europaea L. cv. Picual during olive ripening, we identify and quantify the concentration of Htyr, Tyr, and Ole by reversed-phase high-performance liquid chromatography (RP-HPLC). Rain-fed olive trees, 30 years old, under traditional cultivation were studied in Jaén (Spain). From August to November, seven representative samples of the ripening process were taken. RESULTS The concentration of these phenolic compounds proved higher in the stems than in the roots. From the middle of September to October the Htyr and Tyr concentration significantly increased in stems. The Ole concentration increased from the middle of September to the end of November. In the roots, the concentration of Htyr and Ole significantly declined during ripening. CONCLUSION Ole, Htyr, and Tyr are present in the stems and roots of the olive tree and significantly change in concentration during ripening, demonstrating the involvement of these compounds in the metabolism of both organs during this phase.
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Petasites hybridus root (butterbur) is an effective preventive treatment for migraine.
Lipton, RB, Göbel, H, Einhäupl, KM, Wilks, K, Mauskop, A
Neurology. 2004;(12):2240-4
Abstract
OBJECTIVE To evaluate the clinical efficacy of a standardized special root extract from the plant Petasites hybridus as a preventive therapy for migraine. METHODS This is a three-arm, parallel-group, randomized trial comparing Petasites extract 75 mg bid, Petasites extract 50 mg bid, or placebo bid in 245 patients with migraine. Eligible patients met International Headache Society criteria for migraine, were ages 18 to 65, and had at least two to six attacks per month over the preceding 3 months. The main outcome measure was the decrease in migraine attack frequency per month calculated as percentage change from baseline over a 4-month treatment period. RESULTS Over 4 months of treatment, in the per-protocol analysis, migraine attack frequency was reduced by 48% for Petasites extract 75 mg bid (p = 0.0012 vs placebo), 36% for Petasites extract 50 mg bid (p = 0.127 vs placebo), and 26% for the placebo group. The proportion of patients with a > or =50% reduction in attack frequency after 4 months was 68% for patients in the Petasites extract 75-mg arm and 49% for the placebo arm (p < 0.05). Results were also significant in favor of Petasites 75 mg at 1, 2, and 3 months based on this endpoint. The most frequently reported adverse reactions considered possibly related to treatment were mild gastrointestinal events, predominantly burping. CONCLUSIONS Petasites extract 75 mg bid is more effective than placebo and is well tolerated as a preventive therapy for migraine. Petasites 50 mg PO bid was not significantly more effective than placebo on the primary study endpoints.
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9.
Root : shoot ratios, optimization and nitrogen productivity.
Agren, GI, Franklin, O
Annals of botany. 2003;(6):795-800
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Abstract
Plants respond to nitrogen availability by changing their root : shoot ratios. One hypothesis used to explain this allocation is that plants optimize their behaviour by maximizing their relative growth rate. The consequences of this hypothesis were investigated by formulating two models for root : shoot allocation, with and without explicit inclusion of maintenance respiration. The models also took into account that relative growth rate is a linear function of plant nitrogen concentration. The model without respiration gave qualitatively reasonable results when predictions were compared with observed results from growth experiments with birch and tomato. The explicit inclusion of maintenance respiration improved considerably the agreement between prediction and observation, and for birch was within the experimental accuracy. Further improvements will require additional details in the description of respiratory processes and the nitrogen uptake function. Plants growing under extreme nutrient stress may also optimize their behaviour with respect to other variables in addition to relative growth rate.
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10.
[The population genetics of nodule bacteria].
Provorov, NA
Zhurnal obshchei biologii. 2000;(3):229-57
Abstract
The data are reviewed on the population structure and evolutionary dynamics of the nodule bacteria (rhizobia) which are among the most intensively studied microorganisms. High level of the population polymorphism was demonstrated for the rhizobia populations using the enzyme electrophoresis (MLEE profiles). The average value of Nei's coefficient of heterogeneity (H = 1 - sigma pi2 [n/(n - 1)]) were: 0.590 for rhizobia (Rhizobium, Bradyrhizobium), 0.368 for enterobacteria (Escherichia, Salmonella, Shigella) and 0.452 for pathogenic bacteria (Bordetella, Borrelia, Erysipelothrix, Haemophilus, Helicobacter, Listeria, Mycobacterium, Neisseria, Staphylococcus) populations. In spite of being devoid of the effective systems for the gene conjugative transfer, many rhizobia populations possess an essentially panmictic structure. However, the enterobacteria populations in which the gene transfer may be facilitated due to the conjugative F- and R-factors, usually display the clonal population structure. The legume host plant is proved to be a key factor that determines the high levels of polymorphism and of panmixis as well as high evolutionary rates of the symbiotic bacteria populations. The host may ensure: a) an increase in mutation and gene transfer frequencies; b) stimulation of the competitive (selective) processes in both symbiotic and free-living rhizobia populations. A "cyclic" model of the rhizobia microevolution is presented which allows to assess the inputs the interstrain competition for the saprophytic growth and for the host nodulation into evolution of a plant-associated rhizobia population. The nodulation competitiveness in the rhizobia populations is responsible for the frequency-dependent selection of the rare genotypes which may arise in the soil bacterial communities as a result of the transfer of symbiotic (sym) genes from virulent rhizobia strains to either avirulent rhizobia or to the other (saprophytic, phytopathogenic) bacteria. Therefore, the nodulation competitiveness may ensure: a) panmictic structure of the natural rhizobia populations; b) high taxonomic diversity of rhizobia which was apparently caused by a broad sym gene expansion in the soil bacterial communities. The kin selection models are presented which explain evolution of the "altruistic" (essential for the host plant, but not for the bacteria themselves) symbiotic traits (e.g., the ability for symbiotic nitrogen fixation and for differentiation into non-viable bacteroids) in the rhizobia populations. These models are based on preferential multiplication of the nitrogen-fixing clones either in planta (due to an elevated supply of the nitrogen-fixing nodules with photosynthates) or ex planta (due to a release of the rhizopines from the nitrogen-fixing nodules). Speaking generally, interactions with the host plants provide a range of mechanisms increasing a genetic heterogeneity and an evolutionary potential in the associated rhizobia populations.