Ricardo Fabiano Hettwer Giehl

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Verified

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• PhD
• Co-leader Molecular Plant Nutrition at Leibniz Institute of Plant Genetics and Crop Plant Research

To mobilize sparingly available phosphorus (P) in the rhizosphere, many plant species secrete malate to release P sorbed onto (hydr)oxides of aluminum and iron (Fe). In the presence of Fe, malate can provoke Fe over-accumulation in the root apoplast, triggering a series of events that inhibit root growth. Here, we identified HYPERSENSITIVE TO LOW P...

Many non-graminaceous species release various coumarins in response to iron (Fe) deficiency. However, the physiological relevance of these coumarins remains poorly understood. Here, we show that the three enzymes leading to sideretin biosynthesis co-exist in Arabidopsis (Arabidopsis thaliana) epidermal and cortical cells and that the shift to fraxe...

Cell type-specific mapping of element distribution is critical to fully understand how roots partition nutrients and toxic elements with aboveground parts. In this study, we developed a method that combines fluorescence-activated cell sorting (FACS) with inductively coupled plasma mass spectrometry (ICP-MS) to assess the ionome of different cell po...

In plants, phosphate (Pi) homeostasis is regulated by the interaction of PHR transcription factors with stand-alone SPX proteins, which act as sensors for inositol pyrophosphates. Here, we combined different methods to obtain a comprehensive picture of how inositol (pyro)phosphate metabolism is regulated by Pi and dependent on the inositol phosphat...

Abstract Ammonium uptake in plant roots is mediated by AMT/MEP/Rh-type ammonium transporters. Out of five AMTs being expressed in Arabidopsis roots, four AMT1-type transporters contribute to ammonium uptake, whereas no physiological function has so far been assigned to the only homolog belonging to the MEP subfamily, AMT2;1. Based on the observatio...

Rice (Oryza sativa L.) is a staple food for half of the world population, but lacks essential nutrients such as iron (Fe). Fe deficiency is one of the most common nutritional problems in humans, and biofortification of rice grains is a cost-effective approach to deliver more Fe to people diet. Two Vacuolar Iron Transporters, OsVIT1 and OsVIT2, were...

Iron acquisition is a critical challenge for plants, especially in iron-deficient soils. Recent research underscores the importance of root-exuded coumarins in modulating the root microbiome community structure and facilitating iron uptake. However, interactions between root-associated fungi and coumarins in plant iron nutrition remain unknown. We...

Inositol pyrophosphates (PP-InsPs) are important signaling molecules that regulate diverse cellular processes in eukaryotes, including energy homeostasis and phosphate (Pi) signaling. However, the enzymes responsible for their turnover in plants remain largely unknown. Using a non-hydrolysable PP-InsP analog in a pull-down approach, we identified a...

Root hairs (RH) as mixed tip- and non-tip growing protrusions that develop from root epidermal cells are important for nutrient, and water uptake as well as for root anchoring and interaction with soil microorganisms. Although nutrient availability and temperature are key interlinked factors for a sustained plant growth, the molecular mechanisms un...

Vascular plants have segmented body axes with iterative nodes and internodes. Appropriate node initiation and internode elongation are fundamental to plant fitness and crop yield; however, how these events are spatiotemporally coordinated remains elusive. We show that in barley (Hordeum vulgare L.), selections during domestication have extended the...

Article A spatially concerted epidermal auxin signaling framework steers the root hair foraging response under low nitrogen Graphical abstract Highlights d Plants elongate root hairs to ensure better growth in nitrogen-poor soil d Low N triggers expression of TAA1 and YUC8 to increase auxin levels in root tips d AUX1-and PIN2-mediated auxin transpo...

Vascular plants segment their body axis with iterative nodes of lateral branches and internodes. Appropriate node initiation and internode elongation are fundamental to plant fitness and crop yield formation; but how they are spatiotemporally coordinated remains elusive. We show that in barley (Hordeum vulgare L.), selections under domestication ha...

AMMONIUM TRANSPORTER/METHYLAMMONIUM PERMEASE/RHESUS (AMT) family members transport ammonium across membranes in all life domains. Plant AMTs can be categorized into AMT1 and AMT2 subfamilies. Functional studies of AMTs, particularly AMT1-type, have been conducted using model plants but little is known about the function of AMTs from crops. Sugarcan...

The combinatorial phosphorylation of myo-inositol results in the generation of different inositol phosphates (InsPs), of which phytic acid (InsP6) is the most abundant species in eukaryotes. InsP6 is also an important precursor of the higher phosphorylated inositol pyrophosphates (PP-InsPs), such as InsP7 and InsP8, which are characterized by a dip...

The generation of haploid plants accelerates the crop breeding process. One of the haploidization strategies is based on the genetic manipulation of endogenous CENH3. To extend the haploidization toolbox, we tested whether targeted in vivo degradation of CENH3 protein can be harnessed to generate haploids in Arabidopsis thaliana. We show that a rec...

NGATHA-Like 1 (NGAL1) transcription factor has been identified as a gene regulated through AUG-stop-mediated boron (B)-dependent translation stall (Tanaka et al., 2016); however, its function in B response remains unknown. Here, we show that NGAL1 plays an important role in maintenance of B transport under both low and high B conditions in Arabidop...

Inositol pyrophosphates are signaling molecules containing at least one phosphoanhydride bond that regulate a wide range of cellular processes in eukaryotes. With a cyclic array of phosphate esters and diphosphate groups around myo-inositol, these molecular messengers possess the highest charge density found in nature. Recent work deciphering inosi...

Inositol pyrophosphates are signaling molecules containing at least one phosphoanhydride bond that regulate a wide range of cellular processes in eukaryotes. With a cyclic array of phosphate esters and diphosphate groups around myo -inositol, these molecular messengers possess the highest charge density found in nature. Recent work deciphering inos...

Despite serving as a major inorganic nitrogen source for plants, ammonium causes toxicity at elevated concentrations, inhibiting root elongation early on. While previous studies have shown that ammonium-inhibited root development relates to ammonium uptake and formation of reactive oxygen species (ROS) in roots, it remained open which mechanisms ar...

Optimal plant development requires root uptake of 14 essential mineral elements from the soil. Since the bioavailability of these nutrients underlies large variation in space and time, plants must dynamically adjust their root system architecture to optimize nutrient access and acquisition. The information on external nutrient availability and whol...

Key message SelectiveArabidopsis thalianainositol phosphate kinase functions modulate response amplitudes in innate immunity by balancing signalling adjustments with phosphate homeostasis networks. Abstract Pyrophosphorylation of InsP6 generates InsP7 and/or InsP8 containing high-energy phosphoanhydride bonds that are harnessed during energy requi...

The metals iron, zinc, manganese, copper, molybdenum, and nickel are essential for the growth and development of virtually all plant species. Although these elements are required at only relatively low amounts, natural factors and anthropogenic activities can significantly affect their availability in soils, inducing deficiencies or toxicities in p...

Lateral roots (LRs) dominate the overall root surface of adult plants and are crucial for soil exploration and nutrient acquisition. When grown under mild nitrogen (N) deficiency, flowering plants develop longer LRs to enhance nutrient acquisition. This response is partly mediated by brassinosteroids (BR) and yet unknown mechanisms. Here, we show t...

The availability of iron (Fe) is highly limited for plant uptake in calcareous soils. To overcome this challenge, plants have developed different strategies of Fe mobilization. Non-gramineous species employ a reduction-based strategy (strategy I), which is assisted by the release of Fe(III)-chelating and -reducing coumarins. In this study, the coum...

For more than two decades, Arabidopsis thaliana plants have been routinely grown in vitro within transparent Petri dishes containing agar-based solid media. Although convenient to study root developmental, nutritional and morphological responses to abiotic cues and to elucidate gene functions following reverse and forward genetic approaches, this s...

29 The combinatorial phosphorylation of myo-inositol results in the generation of different inositol 30 phosphates (InsP), of which phytic acid (InsP6) is the most abundant species in eukaryotes. InsP6 31 is also the precursor of higher phosphorylated forms called inositol pyrophosphates (PP-InsPs), 32 such as InsP7 and InsP8, which are characteriz...

In plants, phosphate (P i ) homeostasis is regulated by the interaction of P i starvation response transcription factors (PHRs) with stand-alone SPX proteins, which act as sensors for inositol pyrophosphates (PP-InsPs). Recently, ITPK1 was shown to generate the PP-InsP InsP 7 from InsP 6in vitro , but the importance of this activity in P i signalin...

Root developmental plasticity enables plants to adapt to limiting or fluctuating nutrient conditions in the soil. When grown under nitrogen (N) deficiency, plants develop a more exploratory root system by increasing primary and lateral root length. However, mechanisms underlying this so-called foraging response have remained poorly understood. By p...

Root developmental plasticity enables plants to adapt to limiting or fluctuating nutrient conditions in the soil. When grown under nitrogen (N) deficiency, plants develop a more exploratory root system by increasing primary and lateral root length. However, mechanisms underlying this so-called foraging response have remained poorly understood. By p...

The root system of barley plants is composed of embryogenic, seminal roots, as well as lateral and nodal roots that are formed post-embryonically from seminal roots and from the basal part of shoots, respectively. Due to their distinct developmental origin, seminal and nodal roots may differ in function during plant development, however, a clear co...

The combinatorial phosphorylation of myo-inositol results in the generation of different inositol phosphates (InsP), of which phytic acid (InsP 6 ) is the most abundant species in eukaryotes. InsP 6 is also the precursor of higher phosphorylated forms called inositol pyrophosphates (PP-InsPs), such as InsP 7 and InsP 8 , which are characterized by...

Contamination of soils with heavy metals, such as nickel (Ni), is a major environmental concern due to increasing pollution from industrial activities, burning of fossil fuels, incorrect disposal of sewage sludge, excessive manure application, and the use of fertilizers and pesticides in agriculture. Excess Ni induces leaf chlorosis and inhibits pl...

Diphospho-myo-inositol polyphosphates, also termed inositol pyrophosphates, are molecular messengers containing at least one high-energy phosphoanhydride bond and regulate a wide range of cellular processes in eukaryotes. While inositol pyrophosphates InsP7 and InsP8 are present in different plant species, both the identity of enzymes responsible f...

Developmental plasticity of root system architecture is crucial for plant performance in nutrient-poor soils. Roots of plants grown under mild nitrogen (N) deficiency show a foraging response characterized by increased root length but mechanisms underlying this developmental plasticity are still elusive. By employing natural variation in Arabidopsi...

Silicon (Si) can alleviate cadmium (Cd) toxicity in many plants, but mechanisms underlying this beneficial effect are still lacking. In this study, the roles of Si in time-dependent apoplastic and symplastic Cd absorption by roots of wheat plants were investigated. Results showed that, during short-term Cd exposure, the symplastic pathway of Cd in...

As sessile organisms, plants rely on their roots to acquire sufficient water and nutrients from the soil. Making the right choice about where to deploy new roots can determine survival, especially when soil resources are scarce and unevenly distributed. Recently, it was discovered that plant roots can respond to gradients of soil moisture by favori...

In plants, nutrient provision of shoots depends on the uptake and transport of nutrients across the root tissue to the vascular system. Nutrient delivery to the vasculature is mediated via the apoplastic transport pathway (ATP), which uses the free space in the cell walls and is controlled by apoplastic barriers and nutrient transporters at the end...

Relative transcript levels of AMT1;1, AMT1;2, and AMT1;3 in roots of WT and sgn3 mutant plants. Relative transcript levels were analyzed by real-time PCR using 3 reference genes: Actin 2, ubiquitin 2, and ubiquitin 10. Results were normalized by geNorm software. Since V2/3 < 0.15, the optimal number of internal control genes for this experiment was...

Element concentrations in shoots of WT, sgn3, tko, and tko sgn3 plants. Element concentrations were analyzed by (HR-ICP-MS). Values represent means ± SD (n = 4 biological replicates). Different letters indicate significant differences according to Tukey’s multiple test at p < 0.05. Underlying data can be found in S1 Data. HR-ICP-MS, high-resolution...

Primers used for genotyping and qPCR. All primer sequences are in 5′- to 3′-orientation. (DOCX)

Role of the endodermal bypass for Sr2+ and NH4+ accumulation in roots. Accumulation of Sr2+ (A, B) or 15NH4+ (C, D) in roots of WT (Columbia-0) and sgn3 plants when supplied at an external concentration of 200 μM or 4 mM. Plants were grown under the same conditions as in Fig 1. Bars represent means ± SD. P values were calculated using Student t tes...

Ammonium accumulation rates in different mutants with defects in apoplastic barrier formation. Shoot or root dry weights (A and C) and shoot or root accumulation (B and D) of 15NH4+ in WT (Columbia-0), sgn3, esb1, and myb36 mutant plants. Plants were exposed to 200 μM (A and B) or 4 mM (C and D) 15NH4+. Bars represent means ± SD (n = 4 biological r...

Impact of radial transport pathways on 15NH4+ accumulation in roots. 15N accumulation in roots of tko, tko+1;2, tko+1;3, tko sgn3, tko sgn3+1;2, and tko sgn3+1;3 lines at 200 μM (A–B) or 4 mM (C–D) external 15NH4+. The estimated contribution of ATP or STP in absence or presence of an EB at 200 μM (B) or 4 mM 15NH4+ (D). Values were calculated by su...

Shoot phenotype, potassium (K) and total nitrogen (N) concentrations in shoots of WT, sgn3, tko, and tko sgn3 lines. (A) Phenotype of shoots at the time of sampling. Plants were grown hydroponically for 5 weeks in nutrient solution containing 2 mM NO3- followed by 3 d of N starvation. Scale bars = 1 cm. The experiment was repeated 3 times and repre...

Distribution of apoplastic barriers along the primary root axis in mutant lines. (A) Establishment of functional CSs, determined by the number of endodermal cells after onset of elongation, at which PI penetration to the stele is blocked. Continuous bars indicate that PI was not blocked up to >40 cells. (B and C) Quantification of the distribution...

Relative contribution of individual pathways to radial ammonium transport in different zones along the primary root. Radial transport rates were calculated on the basis of normalized 15N shoot accumulation corresponding to values shown in Fig 2B–2E. (Underlying data can be found in S1 Data). The contribution of each pathway was calculated by subtra...

Determination of radial transport rates in roots. (A) Schematic representation of radial nutrient movement across the root and contribution of root pressure and transpiration to nutrient translocation to the shoot. (B) 15N accumulation rates in roots, shoots, and xylem sap of WT plants supplied with 200 μM 15NH4+. The data represent means ± SD (n =...

Shoot growth phenotype and presence of functional CSs in mutant lines. (A) Shoot growth of tko, tko+1;2, tko+1;3, tko sgn3, tko sgn3+1;2, and tko sgn3+1;3 mutant lines. All plants were grown hydroponically for 5 weeks in nutrient solution containing 2 mM NO3-, followed by 3 d of N starvation. Scale bars = 1 cm. The experiment was repeated 3 times,...

Spatial distribution of AMT transporters and diffusion barriers along the primary root axis. (A-D) Colocalization of AMT1;2:GFP with CSs in mature (A), middle (B), and young (C) root zones. (E-H) Colocalization of AMT1;3:GFP with CS in mature (E), middle (F), and young (G) root zones. Magenta fluorescence shows penetration of PI into the apoplastic...

The original version of this Article omitted the following from the Acknowledgements: 'We also thank DBT-CREST BT/HRD/03/01/2002.' This has been corrected in both the PDF and HTML versions of the Article.

Iron is an essential but poorly bioavailable nutrient because of its low solubility, especially in alkaline soils. Here, we describe the discovery of a previously undescribed redox-active catecholic metabolite, termed sideretin, which derives from the coumarin fraxetin and is the primary molecule exuded by Arabidopsis thaliana roots in response to...

Phosphate (P) is an essential macronutrient for plant growth. Roots employ adaptive mechanisms to forage for P in soil. Root hair elongation is particularly important since P is immobile. Here we report that auxin plays a critical role promoting root hair growth in Arabidopsis in response to low external P. Mutants disrupting auxin synthesis (taa1)...

Iron is an essential but often poorly bioavailable nutrient due to its low solubility, especially in alkaline soils. Plants have evolved at least two distinct strategies to extract iron from soil: solubilization of ferric iron by phytosiderophores, and reduction to the ferrous form at the root surface followed by direct import. Here, we describe th...

In plants, the excess of several heavy metals mimics Fe deficiency-induced chlorosis indicating a disturbance in Fe homeostasis. To examine at which level heavy metals interfere with Fe-deficiency responses, we carried out an in-depth characterization of Fe-related physiological, regulatory and morphological responses in Arabidopsis thaliana expose...

Metal accumulation in seeds is a prerequisite for germination and establishment of plants but also for micronutrient delivery to humans. To investigate metal transport processes and their interactions in seeds, we focused on METAL TOLERANCE PROTEIN 8 (MTP8), a tonoplast transporter of the Mn subclade of cation diffusion facilitators, which in Arabi...

The nitrate transporter NRT1.1 is a versatile plasma-membrane protein that mediates not only nitrate uptake in roots, but also nitrate sensing and signalling. A study of the structural features of NRT1.1 reveals how this protein can coordinate a range of physiological and morphological responses to nitrate.

During a plant's lifecycle the availability of nutrients in the soil is mostly heterogenous in space and time. Plants are able to adapt to nutrient shortage or localized nutrient availabilities by altering their root system architecture to efficiently exploit or search for soil zones containing the limited nutrient. It has been shown that the defic...

Although iron (Fe) is one of the most abundant elements in the earth's crust, its low solubility in soils restricts Fe uptake by plants. Most plant species acquire Fe by acidifying the rhizosphere and reducing ferric to ferrous Fe prior to membrane transport. However, it is unclear how these plants access Fe in the rhizosphere and cope with high so...

Root growth and development are of outstanding importance for the plant’s ability to acquire water and nutrients from different soil horizons. To cope with fluctuating nutrient availabilities, plants integrate systemic signals pertaining to their nutritional status into developmental pathways that regulate the spatial arrangement of roots. Changes...

The fortification of cereal grains with metal micronutrients is a major target to combat human malnutrition of Fe and Zn. Based on recent studies showing that N fertilization can promote Fe and Zn accumulation in cereal grains, we investigated here the influence of nitrate- or ammonium-based N fertilization on the accumulation of Fe, Zn, and Cu as...

Plant roots show a particularly high variation in their morphological response to different nutrient deficiencies. Although such changes often determine the nutrient efficiency or stress tolerance of plants, it is surprising that a comprehensive and comparative analysis of root morphological responses to different nutrient deficiencies has not yet...

On the search for sparingly available nutrients, plants may alter their root architecture to improve soil exploration. So far, the examples for root system modifications induced by a heterogeneous availability of nutrients have been reported for the macronutrients nitrogen (N) and phosphorous (P). In an attempt to extend this type of knowledge to o...

Root system architecture depends on nutrient availability, which shapes primary and lateral root development in a nutrient-specific manner. To better understand how nutrient signals are integrated into root developmental programs, we investigated the morphological response of Arabidopsis thaliana roots to iron (Fe). Relative to a homogeneous supply...

The aim of this work was to study the effect of different techniques of pre-cooling for the conservation of 'Hy Mark' melons. The following pre-cooling treatments were evaluated: [1] cooling the fruits in the storage chamber (RC), [2] pre-cooling with forced-air (FAPC) until the pulp temperature reached 8 °C, [ 3] pre-cooling in water (WPC) to 8 ºC...

This work was carried out aiming to evaluate the effect of thidiazuron (TDZ) on the quality of 'Gala' apples stored under controlled atmosphere (CA) conditions. Plants were sprayed at full bloom with TDZ at 0, 10, 20, or 40g ha-1 (a.i.). Harvested fruits were then stored in CA with 1.0+2.5, 1.5+2.5 and 1.5+5.0 (kPa O2+kPa CO2), both at 0.5°C. In ad...

The aim of this work was to evaluate storage conditions on the maintenance of the physiochemical qualities in Bluegem blueberry. The experiment was arranged in a complete randomized design , with four replicates and the experimental unit consisted of approximately 400g of fruits. Six storage conditions were evaluated as follows: [ 1 ] Cold storage...

O objetivo deste trabalho foi avaliar a qualidade física e química e a incidência de distúrbios fisiológicos em pêssegos 'Chiripá' submetidos a diferentes formas de pré-resfriamento. Os tratamentos avaliados foram: [1] resfriamento convencional em câmara frigorífica (-0,5°C e UR de 95%); [2] resfriamento sob ar forçado (-1,5°C) até a temperatura da...

O objetivo deste trabalho foi avaliar o efeito da inibição da ação do etileno sobre o amadurecimento e o desenvolvimento de dano causado pelo frio em tomates do tipo não longa vida da cultivar 'Monte Carlo'. O experimento foi conduzindo no delineamento inteiramente casualizado, em esquema fatorial (3x2), com quatro repetições. O Fator A foi compost...

This research aimed to evaluate the effect of inhibiting the ethylene action on the ripening and on the development of chilling injury in non-long life 'Monte Carlo' tomatoes. The experiment was a fatorial (3x2), with storage temperature (20°C, 10°C and 5°C) and the treatment or not of 1.0µL L-1 of 1-methylcyclopropene (1-MCP), a compound that bloc...

Experiments were carried out with objective to evaluate the efficiency of methods for bitter pit prediction in 'Fuji' and 'Braeburn' apples sampled at two harvest dates. Fruits from 6 orchards, three for each cultivar, were sampled earlier (20 days before harvest) and at commercial harvest date. The prediction methods assessed were: infiltration of...

To cope with the variable availability of micronutrients, plants have evolved a complex set of physiological and developmental processes, which are under tight control of short-range and long-range signaling pathways. These signals act at the cellular and whole-plant scale to coordinate micronutrient homeostasis at the systemic and local level. Rec...

Postharvest softening in persimmon is considered to be controlled predominantly by ethylene which is present at very low levels during storage. This work evaluates different polyethylene bags with initial CO2 treatment and with ethylene scrubbing on extending the storage life of ‘Fuyu’ persimmon kept under refrigeration. Fruit were harvested at a ‘...

‘Fuyu’ persimmons were held for three months at -0.5°C in air and controlled atmosphere (CA) storage at 0.5 kPa O2 + 5.0 kPa CO2 associated with phosphite or phosphite and calcium chloride applications, or combined to low relative humidity (LRH) aiming to reduce loss of flesh firmness, decay incidence and skin browning. After three days at 20°C, so...

O objetivo deste trabalho foi avaliar os efeitos da aplicação, em pré e pós-colheita, de fosfitos de potássio e cloretos de benzalcônio no controle de podridões pós-colheita em maçãs ‘Fuji’. No primeiro experimento, os tratamentos foram aplicados, por meio de pulverização, um dia antes da colheita. No segundo, os frutos foram tratados através de im...

The objective of this experiment was to evaluate the gaseous composition and quality maintenance of ‘Gala’ apples, stored within polyethylene (PE) bags of different thickness combined with ethylene absorption, during refrigerated transport. The treatments evaluated were combinations of two PE film thickness [high density polyethylene (HDPE) of 7µm...

This research aimed to evaluate the effect of inhibition the ethylene biosynthesis at the pre-harvest stage, the ethylene action and the absorption from the controlled atmosphere storage room on the quality of 'Gala' apples. The experimental design was entirely randomized, with four replicates and the experimental unit composed by 25 fruits. The tr...

Este trabalho teve por objetivo avaliar o efeito da inibição da biossíntese de etileno no período pré-colheita e o efeito da inibição da ação ou da absorção do etileno durante o armazenamento em atmosfera controlada (AC; 1,2kPa de O2 + 2,5kPa de CO2 a 0°C) sobre a qualidade de maçãs cv. "Gala". Além disso, avaliou-se também o efeito combinado desse...

The objective of this research was to evaluate the effect of temperature and controlled atmosphere (CA) storage conditions on the quality of 'Maciel' peaches harvested in two ripening stages. The treatments were: refrigerated air storage (RA) at +0.5°C; RA at -0.5°C; 2.0kPa O2 + 4.0kPa CO2 plus -0.5°C; 1.0kPa O2 + 3.0kPa CO2 plus -0.5°C; 2.0kPa O2...