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Plants, Volume 8, Issue 1 (January 2019)

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Cover Story (view full-size image) Inspired by his many contributions to the field of cellular and molecular biotechnology in [...] Read more.
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Open AccessArticle Unraveling Morphophysiological and Biochemical Responses of Triticum aestivum L. to Extreme pH: Coordinated Actions of Antioxidant Defense and Glyoxalase Systems
Received: 19 December 2018 / Revised: 13 January 2019 / Accepted: 15 January 2019 / Published: 18 January 2019
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Abstract
Soil pH, either low (acidity) or high (alkalinity), is one of the major constraints that affect many biochemical and biological processes within the cell. The present study was carried out to understand the oxidative damage and antioxidant defense in wheat (Triticum aestivum [...] Read more.
Soil pH, either low (acidity) or high (alkalinity), is one of the major constraints that affect many biochemical and biological processes within the cell. The present study was carried out to understand the oxidative damage and antioxidant defense in wheat (Triticum aestivum L. cv. BARI Gom-25) grown under different pH regimes. Eight-day-old seedlings were exposed to growing media with different pH levels (4.0, 5.5, 7.0, and 8.5). Seedlings grown in pH 4.0 and in pH 8.5 showed reductions in biomass, water, and chlorophyll contents; whereas plants grown at pH 7.0 (neutral) exhibited a better performance. Extremely acidic (pH 4.0) and/or strongly alkaline (pH 8.5)-stress also increased oxidative damage in wheat by excess reactive oxygen species (ROS) generation and methylglyoxal (MG) production, which increased lipid peroxidation and disrupted the redox state. In contrary, the lowest oxidative damage was observed at a neutral condition, followed by a strong acidic condition (pH 5.5), which was mainly attributed to the better performance of the antioxidant defense and glyoxalase systems. Interestingly, seedlings grown at pH 5.5 showed a significant increase in morphophysiological attributes compared with extreme acidic (pH 4.0)- and strong alkaline (pH 8.5)-stress treatments, which indicates the tolerance of wheat to the acidic condition. Full article
(This article belongs to the Section Plant Physiology and Metabolism)
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Open AccessArticle The Costs of Green Leaf Volatile-Induced Defense Priming: Temporal Diversity in Growth Responses to Mechanical Wounding and Insect Herbivory
Received: 30 November 2018 / Revised: 13 January 2019 / Accepted: 16 January 2019 / Published: 18 January 2019
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Abstract
Green leaf volatiles (GLVs) have long been associated with plant defense responses against insect herbivory. Although some of their biological activities appear to directly affect the attacking herbivore, one of the major functions of GLVs seems to be the priming of these defense [...] Read more.
Green leaf volatiles (GLVs) have long been associated with plant defense responses against insect herbivory. Although some of their biological activities appear to directly affect the attacking herbivore, one of the major functions of GLVs seems to be the priming of these defense responses. This priming is generally considered to impose low costs on the plant should no direct attack happen. Here, we demonstrate that priming of maize seedlings with GLVs is costly for the plants as it results in significantly reduced growth. We further demonstrate that priming very selectively affects growth responses after insect elicitor treatment and mechanical wounding depending on the age and/or the developmental stage of the treated plant. The differential growth response of maize seedlings to treatment with GLVs and subsequent herbivory-related damage sheds new light on the biological activity of these important plant volatile compounds and indicates consequences that go beyond defense. Full article
(This article belongs to the Special Issue Plants Interacting with other Organisms: Insects)
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Open AccessArticle Antioxidant and Antimicrobial Activity of Mexican Oregano (Poliomintha longiflora) Essential Oil, Hydrosol and Extracts from Waste Solid Residues
Received: 15 December 2018 / Revised: 13 January 2019 / Accepted: 14 January 2019 / Published: 17 January 2019
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Abstract
Poliomintha longiflora is a Mexican oregano, which has not been widely studied. This work aimed to describe the chemical composition, antimicrobial and antioxidant activities present in P. longiflora essential oil (EO), the hydrosol from EO extraction and extracts from waste solid residues (WSRs), [...] Read more.
Poliomintha longiflora is a Mexican oregano, which has not been widely studied. This work aimed to describe the chemical composition, antimicrobial and antioxidant activities present in P. longiflora essential oil (EO), the hydrosol from EO extraction and extracts from waste solid residues (WSRs), identified as ethanol extract, ethyl acetate extract and the subfractions of ethanol and ethyl acetate extracts. The chemical characterization of the EO, hydrosol and WSR extracts was performed by GC–MS and HPLC. Their antioxidant activity was evaluated using two methods, and their antimicrobial activity was evaluated against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and Salmonella Typhimurium. Thirty-one chemical components were identified in the EO. The subfractions from the ethanol and ethyl acetate extracts contain methylmaleic anhydride, thymoquinone, thymol, carvacrol, thymol acetate, carvacrol acetate, and phenolic acids. The EO presented the highest biological activities for antioxidant (136.05 mg equivalent of ascorbic acid/g (AAE/g); IC50 83.70 μg/mL of 2, 2-diphenyl-1-picrylhydrazyl (DPPH)) and antimicrobial tests (minimal inhibitory concentration (MIC) value of 250–750 mg/L), while the hydrosol and the ethyl acetate extract from WSRs had the lowest antioxidant activity (14.16 and 12.29 mg AAE/g respectively), and the hydrosol had the lowest antimicrobial activity (MIC of 3000 mg/L). The data suggest that Mexican oregano P. longiflora hydrosol and extracts from waste solid residues can still have compounds with antimicrobial and antioxidant capacities. Full article
(This article belongs to the Section Phytochemistry)
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Open AccessArticle Sulfate-Induced Stomata Closure Requires the Canonical ABA Signal Transduction Machinery
Received: 23 November 2018 / Revised: 7 January 2019 / Accepted: 11 January 2019 / Published: 16 January 2019
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Abstract
Phytohormone abscisic acid (ABA) is the canonical trigger for stomatal closure upon abiotic stresses like drought. Soil-drying is known to facilitate root-to-shoot transport of sulfate. Remarkably, sulfate and sulfide—a downstream product of sulfate assimilation—have been independently shown to promote stomatal closure. For induction [...] Read more.
Phytohormone abscisic acid (ABA) is the canonical trigger for stomatal closure upon abiotic stresses like drought. Soil-drying is known to facilitate root-to-shoot transport of sulfate. Remarkably, sulfate and sulfide—a downstream product of sulfate assimilation—have been independently shown to promote stomatal closure. For induction of stomatal closure, sulfate must be incorporated into cysteine, which triggers ABA biosynthesis by transcriptional activation of NCED3. Here, we apply reverse genetics to unravel if the canonical ABA signal transduction machinery is required for sulfate-induced stomata closure, and if cysteine biosynthesis is also mandatory for the induction of stomatal closure by the gasotransmitter sulfide. We provide genetic evidence for the importance of reactive oxygen species (ROS) production by the plasma membrane-localized NADPH oxidases, RBOHD, and RBOHF, during the sulfate-induced stomatal closure. In agreement with the established role of ROS as the second messenger of ABA-signaling, the SnRK2-type kinase OST1 and the protein phosphatase ABI1 are essential for sulfate-induced stomata closure. Finally, we show that sulfide fails to close stomata in a cysteine-biosynthesis depleted mutant. Our data support the hypothesis that the two mobile signals, sulfate and sulfide, induce stomatal closure by stimulating cysteine synthesis to trigger ABA production. Full article
(This article belongs to the Special Issue Advances in Plant Sulfur Research)
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Open AccessReview Lateral Transport of Organic and Inorganic Solutes
Received: 14 November 2018 / Revised: 10 January 2019 / Accepted: 11 January 2019 / Published: 15 January 2019
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Abstract
Organic (e.g., sugars and amino acids) and inorganic (e.g., K+, Na+, PO42−, and SO42−) solutes are transported long-distance throughout plants. Lateral movement of these compounds between the xylem and the phloem, and vice [...] Read more.
Organic (e.g., sugars and amino acids) and inorganic (e.g., K+, Na+, PO42−, and SO42−) solutes are transported long-distance throughout plants. Lateral movement of these compounds between the xylem and the phloem, and vice versa, has also been reported in several plant species since the 1930s, and is believed to be important in the overall resource allocation. Studies of Arabidopsis thaliana have provided us with a better knowledge of the anatomical framework in which the lateral transport takes place, and have highlighted the role of specialized vascular and perivascular cells as an interface for solute exchanges. Important breakthroughs have also been made, mainly in Arabidopsis, in identifying some of the proteins involved in the cell-to-cell translocation of solutes, most notably a range of plasma membrane transporters that act in different cell types. Finally, in the future, state-of-art imaging techniques should help to better characterize the lateral transport of these compounds on a cellular level. This review brings the lateral transport of sugars and inorganic solutes back into focus and highlights its importance in terms of our overall understanding of plant resource allocation. Full article
(This article belongs to the Special Issue Plant Phloem Development)
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Open AccessArticle Phytotoxic and Genotoxic Effects of Copper Nanoparticles in Coriander (Coriandrum sativum—Apiaceae)
Received: 24 October 2018 / Revised: 30 December 2018 / Accepted: 5 January 2019 / Published: 14 January 2019
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Abstract
Engineered metal nanoparticles have been widely used in several applications that may lead to increased exposure to the environment. In this study, we assessed the phytotoxic effect of various concentrations of copper nanoparticles CuNP, (200, 400 and 800 mg/L) on coriander (Coriandrum [...] Read more.
Engineered metal nanoparticles have been widely used in several applications that may lead to increased exposure to the environment. In this study, we assessed the phytotoxic effect of various concentrations of copper nanoparticles CuNP, (200, 400 and 800 mg/L) on coriander (Coriandrum sativum) plants grown hydroponically. C. sativum plants treated with CuNP demonstrated decreased biomass and root length in comparison to control untreated plants. Additionally, decreased levels of photosynthetic pigments (chlorophyll a and b) were also seen in C. sativum plants treated with CuNP, as well as damage to the C. sativum root plasma membrane as demonstrated by Evan’s blue dye and increased electrolyte leakage. Moreover, our results exhibited increased levels of H2O2 and MDA on C. Sativum plants treated with CuNP. X-Ray Fluorescence (XRF) analysis confirmed that C. sativum treated with CuNP accumulated the latter in plant root tissues. Random amplified polymorphic DNA (RAPD) analysis confirmed the genotoxic effect of CuNP, which altered the C. sativum genome. This was shown by the different banding pattern of RAPD. Overall, our results exhibited that CuNP is toxic to C. sativum plants. Full article
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Open AccessReview Plant Cellular and Molecular Biotechnology: Following Mariotti’s Steps
Received: 31 October 2018 / Revised: 30 December 2018 / Accepted: 7 January 2019 / Published: 10 January 2019
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Abstract
This review is dedicated to the memory of Prof. Domenico Mariotti, who significantly contributed to establishing the Italian research community in Agricultural Genetics and carried out the first experiments of Agrobacterium-mediated plant genetic transformation and regeneration in Italy during the 1980s. Following [...] Read more.
This review is dedicated to the memory of Prof. Domenico Mariotti, who significantly contributed to establishing the Italian research community in Agricultural Genetics and carried out the first experiments of Agrobacterium-mediated plant genetic transformation and regeneration in Italy during the 1980s. Following his scientific interests as guiding principles, this review summarizes the recent advances obtained in plant biotechnology and fundamental research aiming to: (i) Exploit in vitro plant cell and tissue cultures to induce genetic variability and to produce useful metabolites; (ii) gain new insights into the biochemical function of Agrobacterium rhizogenes rol genes and their application to metabolite production, fruit tree transformation, and reverse genetics; (iii) improve genetic transformation in legume species, most of them recalcitrant to regeneration; (iv) untangle the potential of KNOTTED1-like homeobox (KNOX) transcription factors in plant morphogenesis as key regulators of hormonal homeostasis; and (v) elucidate the molecular mechanisms of the transition from juvenility to the adult phase in Prunus tree species. Full article
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Open AccessArticle Dimensionless Numbers to Analyze Expansive Growth Processes
Received: 10 December 2018 / Revised: 2 January 2019 / Accepted: 6 January 2019 / Published: 10 January 2019
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Abstract
Cells of algae, fungi, and plants have walls and exhibit expansive growth which can increase their volume by as much as 10,000 times. Expansive growth is central to their morphogenesis, development, and sensory responses to environmental stimuli. Equations describing the biophysical processes of [...] Read more.
Cells of algae, fungi, and plants have walls and exhibit expansive growth which can increase their volume by as much as 10,000 times. Expansive growth is central to their morphogenesis, development, and sensory responses to environmental stimuli. Equations describing the biophysical processes of the water uptake rate and the wall deformation rate have been derived, validated, and established. A significant amount of research provides insight into the molecular underpinnings of these processes. What is less well known are the relative magnitudes of these processes and how they compare during expansive growth and with walled cells from other species. Here, dimensionless numbers (Π parameters) are used to determine the magnitudes of the biophysical processes involved in the expansive growth rate of cells from algae (Chara corallina), fungi (Phycomyces blakesleeanus), and plants (Pisum satinis L.). It is found for all three species that the cell’s capability for the water uptake rate is larger than the wall plastic deformation rate and much larger than the wall elastic deformation rate. Also, the wall plastic deformation rates of all three species are of similar magnitude as their expansive growth rate even though the stress relaxation rates of their walls are very different. It is envisioned that dimensionless numbers can assist in determining how these biophysical processes change during development, morphogenesis, sensory responses, environmental stress, climate change, and after genetic modification. Full article
(This article belongs to the Section Plant Modeling)
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Open AccessArticle Extraction of Carnosic Acid and Carnosol from Sage (Salvia officinalis L.) Leaves by Supercritical Fluid Extraction and Their Antioxidant and Antibacterial Activity
Received: 1 December 2018 / Revised: 28 December 2018 / Accepted: 7 January 2019 / Published: 9 January 2019
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Abstract
Sage (Salvia officinalis L.) is a good source of antioxidant compounds, carnosic acid and carnosol being the prominent ones. Both are soluble in CO2, and our goal was to investigate the application of supercritical CO2 extraction to obtain sage [...] Read more.
Sage (Salvia officinalis L.) is a good source of antioxidant compounds, carnosic acid and carnosol being the prominent ones. Both are soluble in CO2, and our goal was to investigate the application of supercritical CO2 extraction to obtain sage extracts rich in these compounds. The effect of pressure, temperature, and CO2 flow rate on the carnosic acid and carnosol yield was studied. These variables were optimized by response surface methodology (RSM). The pressure significantly affected carnosol extraction, while the extraction of carnosic acid was affected by the pressure, temperature, and CO2 flow rate. Carnosic acid content varied from 0.29–120.0 µg mg−1, and carnosol content from 0.46–65.5 µg mg−1. The optimal conditions according to RSM were a pressure of 29.5 MPa, a temperature of 49.1 °C, and a CO2 flow rate of 3 kg h−1, and the sage extract yield was calculated to be 6.54%, carnosic acid content 105 µg mg−1, and carnosol content 56.3 µg mg−1. The antioxidant activities of the sage extracts were evaluated by the scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH). Sage extract obtained at 30 MPa and 40 °C with 2 kg h−1 CO2 flow rate with a carnosic acid content of 72 µg mg−1 and carnosol content of 55 µg mg−1 exhibited the highest antioxidant activity (80.0 ± 0.68%) amongst the investigated supercritical fluid extracts at 25 µg mL−1 concentration. The antimicrobial properties of extracts were tested on four bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus. The extract with a carnosic acid content of 116 µg mg−1 and a carnosol content of 60.6 µg mg−1 was found to be the most potent agent against B. subtilis. Full article
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Open AccessEditorial Acknowledgement to Reviewers of Plants in 2018
Published: 9 January 2019
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Abstract
Rigorous peer-review is the corner-stone of high-quality academic publishing [...] Full article
Open AccessArticle THROUGH THE LOOKING GLASS: Real-Time Imaging in Brachypodium Roots and Osmotic Stress Analysis
Received: 17 November 2018 / Revised: 23 December 2018 / Accepted: 4 January 2019 / Published: 8 January 2019
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Abstract
To elucidate dynamic developmental processes in plants, live tissues and organs must be visualised frequently and for extended periods. The development of roots is studied at a cellular resolution not only to comprehend the basic processes fundamental to maintenance and pattern formation but [...] Read more.
To elucidate dynamic developmental processes in plants, live tissues and organs must be visualised frequently and for extended periods. The development of roots is studied at a cellular resolution not only to comprehend the basic processes fundamental to maintenance and pattern formation but also study stress tolerance adaptation in plants. Despite technological advancements, maintaining continuous access to samples and simultaneously preserving their morphological structures and physiological conditions without causing damage presents hindrances in the measurement, visualisation and analyses of growing organs including plant roots. We propose a preliminary system which integrates the optical real-time visualisation through light microscopy with a liquid culture which enables us to image at the tissue and cellular level horizontally growing Brachypodium roots every few minutes and up to 24 h. We describe a simple setup which can be used to track the growth of the root as it grows including the root tip growth and osmotic stress dynamics. We demonstrate the system’s capability to scale down the PEG-mediated osmotic stress analysis and collected data on gene expression under osmotic stress. Full article
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Open AccessArticle Variation in Aquaporin and Physiological Responses Among Pinus contorta Families Under Different Moisture Conditions
Received: 11 December 2018 / Revised: 22 December 2018 / Accepted: 31 December 2018 / Published: 6 January 2019
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Abstract
A population of eight open pollinated families of Pinus contorta was selected from sites varying in precipitation regimes and elevation to examine the possible role of aquaporins in adaptation to different moisture conditions. Five Pinus contorta aquaporins encoding PiconPIP2;1, PiconPIP2;2, PiconPIP2;3 [...] Read more.
A population of eight open pollinated families of Pinus contorta was selected from sites varying in precipitation regimes and elevation to examine the possible role of aquaporins in adaptation to different moisture conditions. Five Pinus contorta aquaporins encoding PiconPIP2;1, PiconPIP2;2, PiconPIP2;3, PiconPIP1;2, and PiconTIP1;1 were cloned and detailed structural analyses were conducted to provide essential information that can explain their biological and molecular function. All five PiconAQPs contained hydrophilic aromatic/arginine selective filters to facilitate the transport of water. Transcript abundance patterns of PiconAQPs varied significantly across the P. contorta families under varying soil moisture conditions. The transcript abundance of five PiconPIPs remained unchanged under control and water-stress conditions in two families that originated from the sites with lower precipitation levels. These two families also displayed a different adaptive strategy of photosynthesis to cope with drought stress, which was manifested by reduced sensitivity in photosynthesis (maintaining the same rate) while exhibiting a reduction in stomatal conductance. In general, root:shoot ratios were not affected by drought stress, but some variation was observed between families. The results showed variability in drought coping mechanisms, including the expression of aquaporin genes and plant biomass allocation among eight families of Pinus contorta. Full article
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Open AccessArticle Germinative and Post-Germinative Behaviours of Brassica napus Seeds Are Impacted by the Severity of S Limitation Applied to the Parent Plants
Received: 13 November 2018 / Revised: 24 December 2018 / Accepted: 27 December 2018 / Published: 5 January 2019
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Abstract
In oilseed rape (Brassica napus L.), sulphur (S) limitation leads to a reduction of seed yield and nutritional quality, but also to a reduction of seed viability and vigour. S metabolism is known to be involved in the control of germination sensu [...] Read more.
In oilseed rape (Brassica napus L.), sulphur (S) limitation leads to a reduction of seed yield and nutritional quality, but also to a reduction of seed viability and vigour. S metabolism is known to be involved in the control of germination sensu stricto and seedling establishment. Nevertheless, how the germination and the first steps of plant growth are impacted in seeds produced by plants subjected to various sulphate limitations remains largely unknown. Therefore, this study aimed at determining the impact of various S-limited conditions applied to the mother plants on the germination indexes and the rate of viable seedlings in a spring oilseed rape cultivar (cv. Yudal). Using a 34S-sulphate pulse method, the sulphate uptake capacity during the seedling development was also investigated. The rate of viable seedlings was significantly reduced for seeds produced under the strongest S-limited conditions. This is related to a reduction of germination vigour and to perturbations of post-germinative events. Compared to green seedlings obtained from seeds produced by well-S-supplied plants, the viable seedlings coming from seeds harvested on plants subjected to severe S-limitation treatment showed nonetheless a higher dry biomass and were able to enhance the sulphate uptake by roots and the S translocation to shoots. Full article
(This article belongs to the Special Issue Advances in Plant Sulfur Research)
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Open AccessReview Towards an Understanding of the Molecular Basis of Nickel Hyperaccumulation in Plants
Received: 6 December 2018 / Revised: 28 December 2018 / Accepted: 31 December 2018 / Published: 4 January 2019
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Metal hyperaccumulation is a rare and fascinating phenomenon, whereby plants actively accumulate high concentrations of metal ions in their above-ground tissues. Enhanced uptake and root-to-shoot translocation of specific metal ions coupled with an increased capacity for detoxification and sequestration of these ions are [...] Read more.
Metal hyperaccumulation is a rare and fascinating phenomenon, whereby plants actively accumulate high concentrations of metal ions in their above-ground tissues. Enhanced uptake and root-to-shoot translocation of specific metal ions coupled with an increased capacity for detoxification and sequestration of these ions are thought to constitute the physiological basis of the hyperaccumulation phenotype. Nickel hyperaccumulators were the first to be discovered and are the most numerous, accounting for some seventy-five percent of all known hyperaccumulators. However, our understanding of the molecular basis of the physiological processes underpinning Ni hyperaccumulation has lagged behind that of Zn and Cd hyperaccumulation, in large part due to a lack of genomic resources for Ni hyperaccumulators. The advent of RNA-Seq technology, which allows both transcriptome assembly and profiling of global gene expression without the need for a reference genome, has offered a new route for the analysis of Ni hyperaccumulators, and several such studies have recently been reported. Here we review the current state of our understanding of the molecular basis of Ni hyperaccumulation in plants, with an emphasis on insights gained from recent RNA-Seq experiments, highlight commonalities and differences between Ni hyperaccumulators, and suggest potential future avenues of research in this field. Full article
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Open AccessArticle Functional Characterization of microRNA171 Family in Tomato
Received: 9 December 2018 / Revised: 26 December 2018 / Accepted: 28 December 2018 / Published: 4 January 2019
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Abstract
Deeply conserved plant microRNAs (miRNAs) function as pivotal regulators of development. Nevertheless, in the model crop Solanum lycopersicum (tomato) several conserved miRNAs are still poorly annotated and knowledge about their functions is lacking. Here, the tomato miR171 family was functionally analyzed. We found [...] Read more.
Deeply conserved plant microRNAs (miRNAs) function as pivotal regulators of development. Nevertheless, in the model crop Solanum lycopersicum (tomato) several conserved miRNAs are still poorly annotated and knowledge about their functions is lacking. Here, the tomato miR171 family was functionally analyzed. We found that the tomato genome contains at least 11 SlMIR171 genes that are differentially expressed along tomato development. Downregulation of sly-miR171 in tomato was successfully achieved by transgenic expression of a short tandem target mimic construct (STTM171). Consequently, sly-miR171-targeted mRNAs were upregulated in the silenced plants. Target upregulation was associated with irregular compound leaf development and an increase in the number of axillary branches. A prominent phenotype of STTM171 expressing plants was their male sterility due to a production of a low number of malformed and nonviable pollen. We showed that sly-miR171 was expressed in anthers along microsporogenesis and significantly silenced upon STTM171 expression. Sly-miR171-silenced anthers showed delayed tapetum ontogenesis and reduced callose deposition around the tetrads, both of which together or separately can impair pollen development. Collectively, our results show that sly-miR171 is involved in the regulation of anther development as well as shoot branching and compound leaf morphogenesis. Full article
(This article belongs to the Special Issue The Role of MicroRNAs in Plants)
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Open AccessReview Guard Cell Membrane Anion Transport Systems and Their Regulatory Components: An Elaborate Mechanism Controlling Stress-Induced Stomatal Closure
Received: 1 November 2018 / Revised: 19 November 2018 / Accepted: 16 December 2018 / Published: 3 January 2019
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Abstract
When plants are exposed to drastic environmental changes such as drought, salt or bacterial invasion, rapid stomatal movement confers tolerance to these stresses. This process involves a variety of guard cell expressed ion channels and their complex regulation network. Inward K+ channels [...] Read more.
When plants are exposed to drastic environmental changes such as drought, salt or bacterial invasion, rapid stomatal movement confers tolerance to these stresses. This process involves a variety of guard cell expressed ion channels and their complex regulation network. Inward K+ channels mainly function in stomatal opening. On the other hand, guard cell anion channels play a crucial role in the closing of stomata, which is vital in terms of preventing water loss and bacterial entrance. Massive progress has been made on the research of these anion channels in the last decade. In this review, we focus on the function and regulation of Arabidopsis guard cell anion channels. Starting from SLAC1, a main contributor of stomatal closure, members of SLAHs (SLAC1 homologues), AtNRTs (Nitrate transporters), AtALMTs (Aluminum-activated malate transporters), ABC transporters, AtCLCs (Chloride channels), DTXs (Detoxification efflux carriers), SULTRs (Sulfate transporters), and their regulator components are reviewed. These membrane transport systems are the keys to maintaining cellular ion homeostasis against fluctuating external circumstances. Full article
(This article belongs to the Special Issue Salt and Water Stress Tolerance in Plants)
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Open AccessReview Patterning the Axes: A Lesson from the Root
Received: 22 November 2018 / Revised: 19 December 2018 / Accepted: 24 December 2018 / Published: 31 December 2018
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Abstract
How the body plan is established and maintained in multicellular organisms is a central question in developmental biology. Thanks to its simple and symmetric structure, the root represents a powerful tool to study the molecular mechanisms underlying the establishment and maintenance of developmental [...] Read more.
How the body plan is established and maintained in multicellular organisms is a central question in developmental biology. Thanks to its simple and symmetric structure, the root represents a powerful tool to study the molecular mechanisms underlying the establishment and maintenance of developmental axes. Plant roots show two main axes along which cells pass through different developmental stages and acquire different fates: the root proximodistal axis spans longitudinally from the hypocotyl junction (proximal) to the root tip (distal), whereas the radial axis spans transversely from the vasculature tissue (centre) to the epidermis (outer). Both axes are generated by stereotypical divisions occurring during embryogenesis and are maintained post-embryonically. Here, we review the latest scientific advances on how the correct formation of root proximodistal and radial axes is achieved. Full article
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Open AccessArticle Soil Physics Involvement in the Germination Ecology of Buried Weed Seeds
Received: 24 November 2018 / Revised: 18 December 2018 / Accepted: 22 December 2018 / Published: 29 December 2018
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Abstract
Trials were performed to test the germination ecology of buried weed seeds as a function of physical soil conditions such as of burial depth, texture, and compaction. Indeed, these ecological conditions, due to the adopted agronomic practices, play a crucial role in modulating [...] Read more.
Trials were performed to test the germination ecology of buried weed seeds as a function of physical soil conditions such as of burial depth, texture, and compaction. Indeed, these ecological conditions, due to the adopted agronomic practices, play a crucial role in modulating the seed bank germination dynamics. Experiments were carried out in open fields in confined soils (polypropylene pipes), and in the laboratory in Petri dishes. Sowing depth strongly inhibited the seed germination of the three weed species selected. This inhibition was found to be inversely proportional to the size of the soil particles. Compaction strongly increased the depth-mediated inhibition, especially in soils that were rich in clay particles, and was inversely proportional to the seed size. The physiological nature of the dormancy imposed by burial was investigated. In addition, ungerminated seeds, re-exhumed after deep-sowing for six months, were found to be in deep dormancy, especially after burial in compacted clay soil. This dormancy induction was more pronounced in weed species characterized by small seeds. Critical issues are discussed regarding weed seed bank ecophysiology and their management in sustainable agricultural cropping systems. Full article
(This article belongs to the Special Issue Seed Behavior in Soil)
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Open AccessReview Organogenesis at the Shoot Apical Meristem
Received: 1 November 2018 / Revised: 12 December 2018 / Accepted: 21 December 2018 / Published: 28 December 2018
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Lateral organ initiation at the shoot apical meristem involves complex changes in growth rates and directions, ultimately leading to the formation of leaves, stems and flowers. Extensive molecular analysis identifies auxin and downstream transcriptional regulation as major elements in this process. This molecular [...] Read more.
Lateral organ initiation at the shoot apical meristem involves complex changes in growth rates and directions, ultimately leading to the formation of leaves, stems and flowers. Extensive molecular analysis identifies auxin and downstream transcriptional regulation as major elements in this process. This molecular regulatory network must somehow interfere with the structural elements of the cell, in particular the cell wall, to induce specific morphogenetic events. The cell wall is composed of a network of rigid cellulose microfibrils embedded in a matrix composed of water, polysaccharides such as pectins and hemicelluloses, proteins, and ions. I will discuss here current views on how auxin dependent pathways modulate wall structure to set particular growth rates and growth directions. This involves complex feedbacks with both the cytoskeleton and the cell wall. Full article
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Open AccessArticle Isolation and Characterization of Plant Growth-Promoting Endophytic Fungi from the Roots of Dendrobium moniliforme
Received: 25 August 2018 / Revised: 6 November 2018 / Accepted: 10 November 2018 / Published: 28 December 2018
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Abstract
The present study aims to identify the diverse endophytic fungi residing in the roots of Dendrobium moniliforme and their role in plant growth and development. Nine endophytic fungi were isolated from the root sections and characterized by molecular technique. Quantification of the indole [...] Read more.
The present study aims to identify the diverse endophytic fungi residing in the roots of Dendrobium moniliforme and their role in plant growth and development. Nine endophytic fungi were isolated from the root sections and characterized by molecular technique. Quantification of the indole acetic acid (IAA) compound by these endophytes was done. Further, Chemical profiling of R11 and R13 fungi was done by Gas Chromatography-Mass Spectroscopy (GC-MS). Asymbiotic seed derived protocorms of Rhynchostylis retusa was used for the plant growth assay to investigate the growth promoting activities of the fungal elicitor prepared from the isolated fungi from D. moniliforme. Among the isolated fungi, the relative dominant fungus was Fusarium sp. The R13 and R6 fungi were identified only at the genus level which concludes the fungi are of new species or strain. The indole acetic acid production was relatively higher in R10. Bioactive compound diversity was observed in the organic extract of R11 and R6. The presence of phenolic compound and essential oil suggest their contribution for the antimicrobial and antioxidant properties to their host plant, D. moniliforme. The plant growth assay result concluded, the fungal elicitor prepared from R10, Colletotrichum alatae was the best among all other for the plant growth activities. Full article
(This article belongs to the Special Issue Plants Interacting with other Organisms: Insects)
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Open AccessReview Drawing a Line: Grasses and Boundaries
Received: 3 November 2018 / Revised: 12 December 2018 / Accepted: 18 December 2018 / Published: 25 December 2018
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Abstract
Delineation between distinct populations of cells is essential for organ development. Boundary formation is necessary for the maintenance of pluripotent meristematic cells in the shoot apical meristem (SAM) and differentiation of developing organs. Boundaries form between the meristem and organs, as well as [...] Read more.
Delineation between distinct populations of cells is essential for organ development. Boundary formation is necessary for the maintenance of pluripotent meristematic cells in the shoot apical meristem (SAM) and differentiation of developing organs. Boundaries form between the meristem and organs, as well as between organs and within organs. Much of the research into the boundary gene regulatory network (GRN) has been carried out in the eudicot model Arabidopsis thaliana. This work has identified a dynamic network of hormone and gene interactions. Comparisons with other eudicot models, like tomato and pea, have shown key conserved nodes in the GRN and species-specific alterations, including the recruitment of the boundary GRN in leaf margin development. How boundaries are defined in monocots, and in particular the grass family which contains many of the world’s staple food crops, is not clear. In this study, we review knowledge of the grass boundary GRN during vegetative development. We particularly focus on the development of a grass-specific within-organ boundary, the ligule, which directly impacts leaf architecture. We also consider how genome engineering and the use of natural diversity could be leveraged to influence key agronomic traits relative to leaf and plant architecture in the future, which is guided by knowledge of boundary GRNs. Full article
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Open AccessCommunication Effects of Growth Regulators and Gelling Agents on Ex Vitro Rooting of Raspberry
Received: 31 October 2018 / Revised: 18 December 2018 / Accepted: 20 December 2018 / Published: 22 December 2018
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Abstract
Successful acclimatization and ex vitro rooting are among the key factors reducing the cost of micropropagated plants. We compared the survival of seven Russian cultivars of raspberry (Rubus idaeus) after rooting in vitro and ex vitro. Rooted shoots adapted to nonsterile [...] Read more.
Successful acclimatization and ex vitro rooting are among the key factors reducing the cost of micropropagated plants. We compared the survival of seven Russian cultivars of raspberry (Rubus idaeus) after rooting in vitro and ex vitro. Rooted shoots adapted to nonsterile conditions much better than nonrooted ones, with survival rates of 81%–98% versus 43%–76%, respectively. We studied the effects of different combinations of plant-growth regulators and gelling agents added to a proliferation medium on ex vitro rooting of primocane-fruiting raspberry cultivar “Atlant”. Reducing the agar concentration from 8 to 6.5 g/L increased the multiplication rate, but caused shoot hyperhydricity. The highest survival rate (97.2%) was observed for shoots grown in a medium containing 0.2 and 0.1 mg/L IBA, and gelled with 5 g/L agar and 0.2 g/L Phytagel. The microshoot height at the multiplication stage did not correlate with the plant growth during acclimatization. The obtained results can be used in the commercial micropropagation of the raspberry. Full article
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Open AccessArticle The Effect of Granular Commercial Fertilizers Containing Elemental Sulfur on Wheat Yield under Mediterranean Conditions
Received: 1 November 2018 / Revised: 12 December 2018 / Accepted: 17 December 2018 / Published: 20 December 2018
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Abstract
The demand to develop fertilizers with higher sulfur use efficiency has intensified over the last decade, since sulfur deficiency in crops has become more widespread. The aim of this study was to investigate whether fertilizers enriched with 2% elemental sulfur (ES) via a [...] Read more.
The demand to develop fertilizers with higher sulfur use efficiency has intensified over the last decade, since sulfur deficiency in crops has become more widespread. The aim of this study was to investigate whether fertilizers enriched with 2% elemental sulfur (ES) via a binding material of organic nature improve yield when compared to the corresponding conventional ones. Under the scanning electron microscope, the granules of the ES-containing fertilizer were found to be covered by a layer of crystal-like particles, the width of which was found to be up to 60 μm. Such a layer could not be found on the corresponding conventional fertilizer granules. Several fertilization schemes with or without incorporated ES were tested in various durum wheat varieties, cultivated in commercial fields. The P-Olsen content of each commercial field was found to be correlated with the corresponding relative change in the yields (YF/YFBES) with a strong positive relationship. The content of 8 ppm of available soil phosphorus was a turning point. At higher values the incorporation of ES in the fertilization scheme resulted in higher yield, while at lower values it resulted in lower yield, compared with the conventional one. The experimental field trials that established following a randomized block design, were separated in two groups: One with P-Olsen ranging between 18–22 ppm and the other between 12–15 ppm, the results of which corroborated the aforementioned finding. The use of ES in all portions of fertilization schemes provided higher relative yields. The coexistence of ES with sulfate in the granule was more efficient in terms of yield, when compared to the granule enriched with ES alone under the same fertilization scheme and agronomic practice. The application of fertilizer mixtures containing the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), ES and ammonium sulfate resulted in even higher relative yields. Yield followed a positive linear relationship with the number of heads per square meter. In this correlation, the P-Olsen content separated the results of the two groups of blocks, where the applied linear trend line in each group presented the same slope. Full article
(This article belongs to the Special Issue Advances in Plant Sulfur Research)
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Open AccessArticle Phytochemistry of Three Ecuadorian Lamiaceae: Lepechinia heteromorpha (Briq.) Epling, Lepechinia radula (Benth.) Epling and Lepechinia paniculata (Kunth) Epling
Received: 27 November 2018 / Revised: 11 December 2018 / Accepted: 15 December 2018 / Published: 20 December 2018
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Abstract
In this research, the leaves of Lepechinia heteromorpha (Briq.) Epling, Lepechinia radula (Benth.) Epling and Lepechinia paniculata (Kunth) Epling have been collected in order to perform a phytochemical study. The first species was distilled to obtain a novel essential oil (EO), while the [...] Read more.
In this research, the leaves of Lepechinia heteromorpha (Briq.) Epling, Lepechinia radula (Benth.) Epling and Lepechinia paniculata (Kunth) Epling have been collected in order to perform a phytochemical study. The first species was distilled to obtain a novel essential oil (EO), while the others were submitted to ethyl acetate extraction and secondary metabolite isolation. The chemical composition of the EO from L. heteromorpha has been investigated by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography with Retention Indices (GC(RI)), identifying 25 constituents. A major compound, (−)-ledol (21.2%), and a minor compound, (−)-caryophyllene oxide (1.0%), were isolated from the EO and their structures confirmed by Nuclear Magnetic Resonance (NMR) spectroscopy. Other major constituents of the EO were viridiflorene (27.3%), (E,E)-α-farnesene (1.4%), spirolepechinene and (E)-β-caryophyllene (7.1% each), allo-aromadendrene (6.1%), camphor (1.7%), limonene (1.3%) and β-phellandrene (4.6%). The enantiomeric composition of the EO monoterpene fraction was also studied, determining the enantiomeric excess and distribution of α-pinene, limonene, β-phellandrene and camphor. The ethyl acetate extract of L. radula and L. paniculata were fractionated by column chromatography. Spathulenol, angustanoic acid E and 5-hydroxy-4′,7-dimethoxy flavone were isolated from L. radula extract; ledol, guaiol and (−)-carnosol were found in L. paniculata. Full article
(This article belongs to the Section Phytochemistry)
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