Browsing by Subject "Zinc"

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Comprehensive analyses of DNA methylation profile, regulation on flowering, and seed mineral accumulation in Arabidopsis thaliana in response to zinc deficiency
(2016) Chen, Xiaochao; Ludewig, Uwe
Zinc (Zn) is an essential micronutrient for plant growth and development, which plays important roles in DNA binding, metabolic, catalytic and transcriptional regulator activities. However, Zn deficiency is a worldwide problem due to its limited bioavailability in soils in many agricultural areas, often as a result of high CaCO3 content and high pH. In addition, phytic acid is able to strongly chelate cations, such as Zn2+, Fe2+, Ca2+ and Mg2+ to form the phytate salts. Phytate cannot be digested by human beings or other monogastric animals due to lack of phytase, an enzyme that can hydrolyze phytate. Therefore, Zn bioavailability in seeds (or grains) is restricted by phytate. Moreover, seed Zn concentration is also reduced by elevated CO2, especially in C3 plants, such as wheat, rice and soybean. Regarding to the crucial roles but limited bioavailability of Zn, here I present a comprehensive analysis on roots, leaves (and flowering) and seeds in response to Zn deficiency in the model plant Arabidopsis thaliana via three experiments. First, I investigated the transcriptional response and whole-genome DNA methylation profile upon Zn deficiency in roots using next-generation sequencing. Ionome analysis on shoots showed that Zn concentration was strongly reduced in Zn deficiency, whereas other nutrients were not affected. Microarray Analysis identified several known Zn-deficiency responsive genes, confirming the effectiveness of Zn deficiency in this work. However, bisulfite sequencing results revealed that DNA methylation was eliminated by Zn deficiency in transposable elements and slightly in gene bodies as well. The DNA demethylation response to nutrient stress was a novel finding, as reversed to previous reports about phosphate stress which accumulated methylation. Surprisingly, further analysis suggested that DNA methylation occurred independent of gene transcription. Nevertheless, non-CpG methylation has a potential impact on flower development in response to Zn deficiency. The second experiment investigated the relationship between rosette size and flowering, and how rosette size and flowering time were regulated by Zn deficiency. Using natural variation population (168 Arabidopsis accessions), I found that flowering time was positively correlated with rosette size in early-flowering accessions but not in late-flowering accessions. Intriguingly, the flowering time was delayed by Zn deficiency in these early-flowering plants and resulting in promotion of vegetative biomass. However, Zn-regulated flowering time was independent of previously reported flowering pathways. Then genome-wide association study identified the underlying candidate gene was FLOWERING LOCUS T (FT) which was strongly inhibited by Zn deficiency in all accessions. Detailed genetic analysis confirmed this result as well. Furthermore, the promotion of leaf size in Zn deficiency was found being contributed by cell proliferation (cell number) but not cell size. Lastly, in the third experiment I was interested in the natural genetic variation in seed Zn concentration, together with iron (Fe) and manganese (Mn), in response to Zn deficiency. Across around 100 accessions, average seed Zn concentration decreased from 47.4 µg g-1 to 31.3 µg g-1 due to Zn deficiency. To identify candidate genes affecting seed Zn, Fe and Mn concentrations, genome-wide association mapping was performed. A candidate gene, inositol 1,3,4-trisphosphate 5/6-kinase 3 gene (ITPK3), was associated which is involved in phytate synthesis pathways. However, loss of this gene in itpk3-1 did neither affect phytate seed levels nor seed Zn, Fe and Mn. Nevertheless, large natural variance of micronutrient seed levels was identified in the population and several accessions maintained high seed Zn despite growth in Zn-deficient conditions. Altogether, this study presents comprehensive analyses in how Arabidopsis adapts to Zn deficiency in regard of root transcription and DNA methylation, flowering and leaf regulation, and seed mineral accumulation. I provided new possibilities of correlation between DNA methylation and gene transcription, which is much more complex than previously reported. I also opened a novel insight into flowering regulation on leaf size, resulting in promotion of vegetative biomass in nutrient deficiency. Substantial natural variation of seed experiment indicated that the evolution process was involved in seed mineral accumulation in Arabidopsis, especially those accessions maintaining Zn concentration in Zn-deficient soils are valuable for further investigations. I believe these findings in Arabidopsis also provide precious knowledge for plant breeders and agronomists who work on crops.
Entwicklung innovativer Pflanzenschutzprodukte und -verfahren als umweltfreundliche Alternativen zur Bekämpfung von Mehltaupilzen : Bericht im Rahmen des Forschungsprojektes: „Silizium als Aktivator bei Kulturpflanzen“
(2019) Raupp, Manfred G.; Weinmann, Markus; Arbeitsgemeinschaft industrieller Forschungsvereinigungen „Otto von Guericke“ e. V. (AiF) Projekt GmbH, Berlin; Madora GmbH, Lörrach; Römheld, Volker; Neumann, Günter; Blaich, Rolf; Merkt, Nikolaus
Powdery mildews are among the most important diseases in many crop plants. In all sectors of crop production (agriculture, viticulture, horticulture and orchards) powdery mildew fungi can cause severe damage under field as well as greenhouse conditions. Although organic synthetic fungicides have been used to combat powdery mildews in conventional and integrated agriculture for decades, organic farming lacks effective alternatives to the ecologically questionable sulfur fungicides. Yet, also for integrated or conventional crop production, alternatives or supplements for a reduction and more effective use of synthetic fungicides would be desirable to optimize the production of high quality food with the help of environmentally friendly means. Objective of the present work was the development of innovative crop protection products and application strategies to combat powdery mildew fungi with respect to the knowledge on resistance-enhancing effects of an improved silicon (Si), manganese (Mn) and zinc (Zn) supply to the plants. Furthermore, various plant extracts have recently received renewed attention. Among other active natural agents, garlic (Allium sativum L.) is known for its fungitoxic effect and at the same time high Mn and Zn contents. With the present work, an overview of possible approaches to control powdery mildew in grapevine by use of Si, Mn, Zn and plant extracts from garlic has been elaborated in greenhouse experiments. In this regard, the physiological significance of Si, Mn and Zn for the expression and strengthening of plant own resistance mechanisms was distinguished from the effectiveness of spray applications for forming passive silicate crusts as mechanical infection barriers. The physiological Si status of the plants could be clearly improved only by soil rather than foliar application of silicates. Regarding the soil application of silicates, however, no practical applications are known, how silicon fertilizers can be distributed under field conditions in the soil and brought into the rhizosphere to continuously ensure high rates of Si uptake. There is also still considerable uncertainty whether the soil application of silicates in non-Si accumulators, such as grapevines, can result in sufficient Si uptake for an effective expression of resistance mechanisms. The most impressive effects in the control of powdery mildew were achieved with the spray application of potassium silicate in combination with wetting agents to form silicate crusts on the leaf surface. The positive influence of Mn and Zn on the effectiveness of spray applications of potassium silicate and the adequate compatibility of Mn and Zn chelates with potassium silicate suggest that the interactions between Si, Mn and Zn should be considered for further product development. The application of garlic extract did not result in sufficient efficiency, although protective and curative properties could be observed. Allicin, supposed to be the active ingredient of garlic extract, has a broad spectrum of antimicrobial activity and is one of the few agents for which no development of resistance has been found in microorganisms so far. Therefore, the interest in this agent for the development of biological plant protection products is expected to increase.
Zinc supplementation effects on phytate degradation, mineral digestibility, and bone characteristics in broiler chickens
(2024) Philippi, Hanna; Rodehutscord, Markus
An adequate supply of phosphorus (P) is important in poultry nutrition, as P is essential for numerous metabolic processes. However, oversupply should be avoided to reduce the environmental impact of poultry production. The main source of P in plant feedstuffs commonly used in poultry nutrition is phytate, the salt form of phytic acid (InsP6). For P from InsP6 to be utilized by animals, it needs to be cleaved by phytases or other phosphatases. However, the capacity of endogenous phosphatases of non-ruminant animals does not suffice to release sufficient P to fulfill the animal’s P requirement. Therefore, commercial poultry diets usually are supplemented with P from mineral sources. By using exogenous phytases, the supplementation of mineral P can be reduced, and finite P reserves can be conserved. To feed poultry without mineral P in the future, phytase efficacy must be improved further. Thus, it is important to know and understand all factors influencing phytase efficacy. The results of in vitro studies have indicated that zinc (Zn) may be an influencing factor. The supplementation of Zn could inhibit phytase activity, with the degree of inhibition depending on the exogenous Zn source used. A literature review on the interactions of Zn with phytate and phytase (Manuscript A of this thesis) has identified a lack of in vivo studies investigating the effects of Zn supplementation on phytase with direct measurements, such as intestinal phytate degradation and prececal P digestibility. Therefore, three in vivo studies were conducted as part of this thesis with the main objective to investigate the effect of Zn supplementation and exogenous Zn source on intestinal phytate degradation in broiler chickens. It was hypothesized that due to the formation of insoluble complexes of Zn and phytate, the supplementation of Zn could reduce phytase efficacy with the extent of reduction depending on the exogenous Zn source. Further, other traits that are affected by Zn supply, such as bone mineralization and gene expression, were also investigated in these in vivo studies. The first experiment (Manuscript B) aimed to determine the effect of dietary Zn level and source on intestinal phytate breakdown, mineral digestibility, bone mineralization, and Zn status without and with exogenous phytase in the feed. Ross 308 broiler chickens were fed experimental diets from day 7 to 28. The basal diet contained 33 mg/kg dry matter native Zn and a high phytate-P concentration to challenge interactions in the digestive tract. The experimental diets differed in the level of exogenous phytase (0 or 750 FTU/kg) and in the Zn source (none, 30 mg/kg of Zn-sulfate, or 30 mg/kg of Zn-oxide). Additionally, two experimental diets with a high Zn supplementation level (90 mg/kg) in the form of Zn-sulfate or Zn-oxide, both containing exogenous phytase, were tested. Intestinal phytate breakdown, P digestibility, and bone mineralization were not affected by Zn source or Zn level but only by phytase supplementation. The concentration of ileal myo-inositol was influenced by phytase × Zn source interaction. Birds fed without phytase supplementation had similarly low myo-inositol concentrations whether they received Zn supplementation or not, whereas birds receiving phytase supplementation and Zn supplementation had significantly higher ileal myo-inositol concentrations than birds fed without Zn supplementation but with phytase supplementation. The missing effect of Zn level or Zn source on phytate degradation indicates that no interactions of Zn and phytate relevant for phytase efficacy occurred in the digestive tract of broilers when Zn was supplemented at levels up to 90 mg/kg in the form of Zn-sulfate or Zn-oxide. Based on the results of the first experiment, where Zn alone did not show relevant interactions with phytate, the second experiment (Manuscript C) aimed to investigate whether the combined supplementation of Zn, copper (Cu), and manganese (Mn) from different sources without and with exogenous phytase in the feed affects intestinal phytate breakdown, prececal mineral digestibility, bone mineralization, and mRNA expression of mineral transporters. Cobb 500 broiler chickens received experimental diets from day 0 to 28. Experimental diets differed in the level of phytase supplementation (0 or 750 FTU/kg) and in the trace mineral source (TMS: 100 mg/kg Zn, 100 mg/kg Mn, and 125 mg/kg Cu as sulfates, oxides, or chelates). Prececal InsP6 disappearance and P digestibility were significantly affected by phytase × TMS interaction. Whereas birds receiving exogenous phytase had similar InsP6 disappearance and P digestibility irrespective of TMS, birds fed without exogenous phytase and with chelated trace minerals had a higher InsP6 disappearance and P digestibility than birds receiving no exogenous phytase and oxides or sulfates. These results indicate that the combined supplementation of Zn, Mn, and Cu at high levels may challenge interactions with phytate in non-phytase-supplemented diets with the extent of interaction depending on the TMS. In phytase-supplemented diets however, the choice of TMS was irrelevant for phytate degradation under the conditions of this study. The third experiment (Manuscript D) aimed to determine the impact of Zn level and Zn source on prececal phytate degradation, mineral digestibility, bone mineralization, and mRNA expression of intestinal (trace) mineral transporters. In contrast to the first experiment, an inorganic Zn source and a chelated Zn source were tested. Cobb 500 broiler chickens received experimental diets from day 0 to 21. The experimental diets differed in Zn supplementation level (10, 30, 50 mg/kg Zn) and exogenous Zn source (Zn-oxide or Zn-glycinate). A cornsoybean meal-based diet without Zn supplementation containing 35 mg/kg native Zn was used as a control. All experimental diets were supplemented with 750 FTU/kg phytase. Prececal InsP6 disappearance, P digestibility, and tibia ash quantity and concentration, and Zn concentration in tibia ash were not affected by diet. Bone breaking strength and tibia width did not differ between treatments. Tibia thickness was lower in the treatments with 30 mg Zn as Zn-oxide and 50 mg Zn as Zn-glycinate than in the treatment with 10 mg Zn as Zn-oxide. The expression of intestinal (trace) mineral transporters was not affected by treatment. These results indicate that in phytase-supplemented diets the native Zn concentration of cornsoybean meal-based diets is satisfactory to achieve maximal Zn concentration in tibia ash during the first 3 weeks of age. The missing effect of Zn level or Zn source on phytate degradation confirms the results from Manuscript B, that Zn and phytate do not interact to a level relevant for phytate degradation by exogenous phytase. It is concluded that contrary to the hypothesis that Zn inhibits phytate degradation by complex formation with phytate, the Zn supplementation up to 100 mg/kg does not appear to influence exogenous phytase efficacy. Minor effects were found on the endogenous phytate degradation if Zn, Cu, and Mn were supplemented combined at high levels, where the extent of reduction in endogenous phytate degradation was dependent on the TMS. It remains unclear whether the inhibiting effect on endogenous phytate degradation occurs only due to the combined supplementation or whether an individual high supplementation of a single trace mineral caused the effect. Further experiments are needed to investigate the effect of Zn on endogenous phosphatases, where the activity of endogenous mucosal activity should be determined in broilers fed diets differing in the Zn supplementation level. Moreover, further experiments are needed to test what level of Zn supplementation is needed in phytase-supplemented diets to ensure the birds sufficient supply in all areas. Besides bone development and growth, effects on the immune system, microbiota composition, and the antioxidative system should be considered.
Zum Einfluß von mikrobieller Phytase und Calcium auf die Blei-, Cadmium und Zinkretention beim wachsenden Schwein
(1997) Zacharias, Bernhard; Drochner, Winfried
In the present study the influence of microbial phytase and/or calcium supplementation in rations of growing pigs (15 to 30 kg resp. 50 kg) on the retention of lead, cadmium and zinc in kidneys, liver, muscles and bones was investigated. The rations consisted of a barley-soy mixture supplemented with lead, cadmium and zinc either in the form of Pb-, Cd- and Zn-polluted barley or of CdCl2, Pb(CH3COO)2, and ZnSO4. The rations contained an average of 1,45 mg Pb, 0,78 mg Cd, and 55,7 mg Zn per kg dry matter and were given either with or without an addition of 800 U microbial phytase per kg. Compared to the reference group the addition of microbial phytase resulted in diets with a nomal calcium supply (6 g/kg) to a significant increase in the concentration of lead in the phalanx 1 and cadmium in kidneys and liver. The zinc concentration, however, only was increased in tendency in bones and liver. By augmenting the calcium concentration to 12 g/kg it was possible to avoid phytase-induced increase in the retention of lead in phalanx 1 and in the deposition of cadmium in kidneys and liver. For zinc, however, this effect of calcium could not be detected. The higher lead concentration in liver, kidneys and bones after addition of Pb(CH3COO)2 may be due to the 51 higher dietary Pb level as compared to the normally polluted barley rations. The reduced Cd-accumulation in livers and kidneys after feeding CdCl2 supplemented diets with a high calcium level may be explained by an increased formation of insoluble cadmium-calcium-phytate that cannot be hydrolysed by phytase. For the heavy metals lead, cadmium, and zinc the addition of phytase might probably result in an increased metal availability due to phytase-induced hydrolysis of the phytate complex. The effect of a calcium supply exceeding the recommended level may be explained by a reduction in the solubility of phytate which results in a decreased ability of phytate to be splitted by phytase and therefore leads to a reduced