Light exposure of roots in aeroponics enhances the accumulation of phytochemicals in aboveground parts of the medicinal plants Artemisia annua and Hypericum perforatum

Light acts as a trigger to enhance the accumulation of secondary compounds in the aboveground part of plants; however, whether a similar triggering effect occurs in roots is unclear. Using an aeroponic setup, we investigated the effect of long term exposure of roots to LED lighting of different wavelengths on the growth andp hytochemical composition of two high-value medicinal plants, Artemisia annua and Hypericum perforatum. In A. annua, root exposure to white, blue, and red light enhanced the accumulation of artemisinin in the shoots by 2.3-, 2.5-, and 1.9-fold, respectively. In H. perforatum, root exposure to white, blue, red, and green light enhanced the accumulation of coumaroylquinic acid in leaves by 89, 65, 84, and 74%, respectively. Root lighting also increased flavonol concentrations. In contrast to its effects in the shoots, root illumination did not change phytochemical composition in the roots or root exudates. Thus, root illumination induces a systemic response, resulting in modulation of the phytochemical composition in distal tissues remote from the light exposure site.publishedVersio

Organic Waste-Based Fertilizer in Hydroponics Increases Tomato Fruit Size but Reduces Fruit Quality

In regions with intensive agricultural production, large amounts of organic waste are produced by livestock animals. Liquid digestate from manure-based biogas production could potentially serve as fertilizer if integrated with closed horticultural irrigation systems. The aim of this experiment was to investigate how fertilizer based on liquid biogas by-products of pig manure digestion can affect the growth and production of tomato plants. Integration of a nitrification bioreactor presumes a significantly lower concentration of nutrient solutions and a higher level of oxygenation than classical mineral cultivation. Therefore, additional controls were included. We compared plant growth and fruit quality traits of tomato plants grown in a hydroponic solution with organic fertilizer with two levels of mineral fertilizer. The tomatoes grown with organic waste-based liquid fertilizer showed reduced growth rates but increased mean fruit size, resulting in no significant change in total yield compared with high-mineral cultivation. The growth rate was similarly reduced in plants cultivated with low-mineral fertilizer. Plants cultivated with organic waste-based fertilizer had high Cl− concentration in xylem sap, leaves, and, ultimately, fruits. The leaves of plants cultivated with organic waste-based fertilizer contained higher concentrations of starch and soluble carbohydrate and low concentrations of phosphorous (P) and sulfur (S). The plants grown with organic waste-based or low-mineral medium showed significantly poorer fruit quality than the plants cultivated with the high-mineral solution. The low-mineral treatment increased xylem sap contribution to fruit weight because of higher root power. The organic waste-based fertilization did not change the root power but increased fruit size. In conclusion, organic waste-based cultivation is a possible solution for sustainable plant production in greenhouses. However, additional adjustment of nutrient supply is required to improve fruit quality

Heterogeneous nutrient supply modulates root exudation and accumulation of medicinally valuable compounds in Artemisia annua and Hypericum perforatum

Plants have evolved complex mechanisms to adapt to nutrient-deficient environments, including stimulating lateral root proliferation into local soil patches with high nutrient content in response to heterogeneous nutrient distribution. Despite the widespread occurrence of this phenomenon in soil, the effect of heterogeneous nutrient distribution on the accumulation of secondary compounds in plant biomass and their exudation by roots remains largely unknown. This study aims to fill this critical knowledge gap by investigating how deficiency and unequal distributions of nitrogen (N), phosphorus (P), and iron (Fe) affect plant growth and accumulation of the antimalarial drug artemisinin (AN) in leaves and roots of Artemisia annua, as well as AN exudation by roots. Heterogeneous N and P supplies strongly increased root exudation of AN in half of a split-root system exposed to nutrient deficiency. By contrast, exposure to a homogeneous nitrate and phosphate deficiency did not modulate root exudation of AN. This indicates that a combination of local and systemic signals, reflecting low and high nutritional statuses, respectively, were required to enhance AN exudation. This exudation response was independent of the regulation of root hair formation, which was predominantly modulated by the local signal. In contrast to the heterogeneous supply of N and P, heterogeneous Fe supply did not modulate AN root exudation but increased AN accumulation in locally Fe-deficient roots. No modulation of nutrient supply significantly changed the accumulation of AN in A. annua leaves. The impact of a heterogeneous nitrate supply on growth and phytochemical composition was also investigated in Hypericum perforatum plants. Unlike in A. annue, the uneven N supply did not significantly influence the exudation of secondary compounds in the roots of H. perforatum. However, it did enhance the accumulation of several biologically active compounds, such as hypericin, catechin, and rutin isomers, in the leaves of H. perforatum. We propose that the capacity of plants to induce the accumulation and/or differential exudation of secondary compounds under heterogeneous nutrient supply is both species- and compound-specific. The ability to differentially exude AN may contribute to A. annua’s adaptation to nutrient disturbances and modulate allelopathic and symbiotic interactions in the rhizosphere

Artificial top-light is more efficient for tomato production than inter-light

Studies of whole-plant responses of tomato to light environments are limited and cannot be extrapolated from observations of seedlings or short-term crops in growth chambers. Effects of artificial light sources like high pressure sodium (HPS) and light emitting diodes (LED) are mainly studied as supplement to sunlight in greenhouses. Since natural sunlight is almost neglectable in Norway during wintertime, we could study effects of different types of artificial light on crop growth and production in tomato. The goal of this experiment was to quantify the effects of artificial HPS top-light, installed at the top of the canopy, and LED inter-light, installed between plant rows, on fresh and dry matter production and fruit quality of greenhouse tomatoes under controlled and documented conditions. Our aim was to optimize yield under different light conditions, while avoiding an unfavourable source-sink balance. Tomato plants were grown under HPS top light with an installed capacity of 161, 242 and 272 W m−2 combined with LED inter-light with an installed capacity of 0, 60 or 120 W m−2. We used stem diameter as a trait to regulate air temperature in different light treatments in order to retain plant vigour. Results show that both HPS top light and LED inter-light increased tomato yield. However, the positive effect of supplemental LED inter-light decreased at higher amounts of HPS top light. Under the conditions in this experiment, with neglectable incoming solar radiation, an installed amount of 242 Watt m-2 HPS top light and a daily light integral (DLI) of 30 mol m-2 day-1 resulted in best light use efficiency (in gram fresh tomato per mol). Addition of LED inter-light to HPS top light reduced light use efficiency. Results show that winter production using artificial light in Norway is more energy efficient compared to production under sunlight in southern countries. Results can be used for modelling purposes.acceptedVersio

The evolution of nuclear auxin signalling

<p>Abstract</p> <p>Background</p> <p>The plant hormone auxin directs many aspects of plant growth and development. To understand the evolution of auxin signalling, we compared the genes encoding two families of crucial transcriptional regulators, <it>AUXIN RESPONSE FACTOR </it>(<it>ARF</it>) and <it>AUXIN/INDOLE-3-ACETIC ACID </it>(<it>Aux/IAA</it>), among flowering plants and two non-seed plants, <it>Physcomitrella patens </it>and <it>Selaginella moellendorffii</it>.</p> <p>Results</p> <p>Comparative analysis of the <it>P. patens, S. moellendorffii </it>and <it>Arabidopsis thaliana </it>genomes suggests that the well-established rapid transcriptional response to auxin of flowering plants, evolved in vascular plants after their divergence from the last common ancestor shared with mosses. An N-terminally truncated ARF transcriptional activator is encoded by the genomes of <it>P. patens </it>and <it>S. moellendorffii</it>, and suggests a supplementary mechanism of nuclear auxin signalling, absent in flowering plants. Site-specific analyses of positive Darwinian selection revealed relatively high rates of synonymous substitution in the <it>A. thaliana </it>ARFs of classes IIa (and their closest orthologous genes in poplar) and Ib, suggesting that neofunctionalization in important functional regions has driven the evolution of auxin signalling in flowering plants. Primary auxin responsive gene families (GH3, SAUR, LBD) show different phylogenetic profiles in <it>P. patens</it>, <it>S. moellendorffii </it>and flowering plants, highlighting genes for further study.</p> <p>Conclusion</p> <p>The genome of <it>P. patens </it>encodes all of the basic components necessary for a rapid auxin response. The spatial separation of the Q-rich activator domain and DNA-binding domain suggests an alternative mechanism of transcriptional control in <it>P. patens </it>distinct from the mechanism seen in flowering plants. Significantly, the genome of <it>S. moellendorffii </it>is predicted to encode proteins suitable for both methods of regulation.</p

Optimising organic vegetable greenhouse production in Denmark

On August 27th, 19 participants, including several organic growers, met in Årslev, Denmark, for a visit to the Greenresilients experimental site. The importance of organic cultivation in the context of the increasing demand for organic vegetables in Denmark was discusse

Auxin-Induced Plasma Membrane Depolarization Is Regulated by Auxin Transport and Not by AUXIN BINDING PROTEIN1

Auxin is a molecule, which controls many aspects of plant development through both transcriptional and non-transcriptional signaling responses. AUXIN BINDING PROTEIN1 (ABP1) is a putative receptor for rapid non-transcriptional auxin-induced changes in plasma membrane depolarization and endocytosis rates. However, the mechanism of ABP1-mediated signaling is poorly understood. Here we show that membrane depolarization and endocytosis inhibition are ABP1-independent responses and that auxin-induced plasma membrane depolarization is instead dependent on the auxin influx carrier AUX1. AUX1 was itself not involved in the regulation of endocytosis. Auxin-dependent depolarization of the plasma membrane was also modulated by the auxin efflux carrier PIN2. These data establish a new connection between auxin transport and non-transcriptional auxin signaling

De-Novo Discovery of Differentially Abundant Transcription Factor Binding Sites Including Their Positional Preference

Transcription factors are a main component of gene regulation as they activate or repress gene expression by binding to specific binding sites in promoters. The de-novo discovery of transcription factor binding sites in target regions obtained by wet-lab experiments is a challenging problem in computational biology, which has not been fully solved yet. Here, we present a de-novo motif discovery tool called Dispom for finding differentially abundant transcription factor binding sites that models existing positional preferences of binding sites and adjusts the length of the motif in the learning process. Evaluating Dispom, we find that its prediction performance is superior to existing tools for de-novo motif discovery for 18 benchmark data sets with planted binding sites, and for a metazoan compendium based on experimental data from micro-array, ChIP-chip, ChIP-DSL, and DamID as well as Gene Ontology data. Finally, we apply Dispom to find binding sites differentially abundant in promoters of auxin-responsive genes extracted from Arabidopsis thaliana microarray data, and we find a motif that can be interpreted as a refined auxin responsive element predominately positioned in the 250-bp region upstream of the transcription start site. Using an independent data set of auxin-responsive genes, we find in genome-wide predictions that the refined motif is more specific for auxin-responsive genes than the canonical auxin-responsive element. In general, Dispom can be used to find differentially abundant motifs in sequences of any origin. However, the positional distribution learned by Dispom is especially beneficial if all sequences are aligned to some anchor point like the transcription start site in case of promoter sequences. We demonstrate that the combination of searching for differentially abundant motifs and inferring a position distribution from the data is beneficial for de-novo motif discovery. Hence, we make the tool freely available as a component of the open-source Java framework Jstacs and as a stand-alone application at http://www.jstacs.de/index.php/Dispom