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Submitted
Hanhan, S. ; Goren, K. ; Rivkin, A. ; Saba, F. ; Nevo, H. ; Dar, N. ; Shilo, D. ; Liebergall, M. ; Shoseyov, O. ; Deutsch, D. ; et al. Regeneration of Grade 3 Ankle Sprain, Using the Recombinant Human Amelogenin Protein (rHAM+), in a Rat Model. Journal of Orthopaedic Research Submitted, n/a. Publisher's VersionAbstract
Abstract Lateral ligament tears, also known as high-grade ankle sprains, are common, debilitating, and usually heal slowly. 10-30% of patients continue to suffer from chronic pain and ankle instability even after 3-9 months. Previously, we showed that the recombinant human amelogenin (rHAM+) induced regeneration of fully transected rat medial collateral ligament (MCL), a common proof-of-concept model. Our aim was to evaluate whether rHAM+ can regenerate torn ankle calcaneo-fibular ligament (CFL), an important component of the lateral ankle stabilizers. Right CFLs of Sabra rats were transected and treated with 0, 0.5 or 1µg/µl rHAM+ dissolved in propylene glycol alginate (PGA). Results were compared to the normal group, without surgery. Healing was evaluated 12 weeks after treatment by mechanical testing (ratio between the right and left, un-transected ligaments of the same rat), and histology including immunohistochemical staining of collagen I and S100. The mechanical properties, structure, and composition of transected ligaments treated with 0.5μg/μl rHAM+ (experimental) were similar to un-transected ligaments. PGA (control) treated ligaments were much weaker, lax and unorganized compared to un-transected ligaments. Treatment with 1μg/μl rHAM+ was not as efficient as 0.5μg/μl rHAM+. Normal arrangement of collagen I fibers and of proprioceptive nerve endings, parallel to the direction of the force, was detected in ligaments treated with 0.5μg/μl rHAM+, and scattered arrangement, resembling scar tissue, in control ligaments. In conclusion, we showed that rHAM+ induced significant mechanical and structural regeneration of torn rat CFLs, which might be translated into treatment for grade 2-3 ankle sprain injuries. This article is protected by copyright. All rights reserved.
2020
Grah, R. ; Friedlander, T. The relation between crosstalk and gene regulation form revisited. PLOS Computational Biology 2020, 16, 1-24. Publisher's VersionAbstract
Author summary Genes differ in the frequency at which they are expressed and in the form of regulation used to control their activity. The basic level of regulation is mediated by different types of DNA-binding proteins, where each type regulates particular gene(s). We distinguish between two basic forms of regulation: positive—if a gene is activated by the binding of its regulatory protein, and negative—if it is active unless bound by its regulatory protein. Due to the multitude of genes and regulators, spurious binding and unbinding events, called “crosstalk”, could occur. How does the form of regulation, positive or negative, affect the extent of regulatory crosstalk? To address this question, we used a mathematical model integrating many genes and many regulators. As intuition suggests, we found that in most of the parameter space, crosstalk increased with the availability of regulators. We propose, that crosstalk is usually reduced when networks are designed such that minimal regulation is needed, which we call the ‘idle’ design. In other words: a frequently needed gene will use negative regulation and conversely, a scarcely needed gene will employ positive regulation. In both cases, the requirement for the regulators is minimized. In addition, we demonstrate how crosstalk can be calculated from available datasets and discuss the technical challenges in such calculation, specifically data incompleteness.
Kumar, S. ; Adiram-Filiba, N. ; Blum, S. ; Sanchez-Lopez, J. A. ; Tzfadia, O. ; Omid, A. ; Volpin, H. ; Heifetz, Y. ; Goobes, G. ; Elbaum, R. Siliplant1 (Slp1) protein precipitates silica in sorghum silica cells. Journal of Experimental Botany 2020. Publisher's VersionAbstract
Silicon is absorbed by plant roots as silicic acid. The acid moves with the transpiration stream to the shoot, and mineralizes as silica. In grasses, leaf epidermal cells called silica cells deposit silica in most of their volume by unknown mechanism. Using bioinformatics tools, we identified a previously uncharacterized protein in sorghum (Sorghum bicolor), which we named Siliplant1 (Slp1). Slp1 is a basic protein with seven repeat units rich in proline, lysine, and glutamic acid. We found Slp1 RNA in sorghum immature leaf and immature inflorescence. In leaves, transcription was highest just before the active silicification zone (ASZ). There, Slp1 was localized specifically to developing silica cells, packed inside vesicles and scattered throughout the cytoplasm or near the cell boundary. These vesicles fused with the membrane, releasing their content in the apoplastic space. A short peptide that is repeated five times in Slp1 precipitated silica in vitro at a biologically relevant silicic acid concentration. Transient overexpression of Slp1 in sorghum resulted in ectopic silica deposition in all leaf epidermal cell-types. Our results show that Slp1 precipitates silica in sorghum silica cells.
Adiram-Filiba, N. ; Geiger, Y. ; Kumar, S. ; Keinan-Adamsky, K. ; Elbaum, R. ; Goobes, G. Peptides from diatoms and grasses harness phosphate ion binding to silica to help regulate biomaterial structure. Acta Biomaterialia 2020. Publisher's VersionAbstract
Many life forms generate intricate submicron biosilica structures with various important biological functions. The formation of such structures, from the silicic acid in the waters and in the soil, is thought to be regulated by unique proteins with high repeats of specific amino acids and unusual sidechain modifications. Some silicifying proteins are characterized by high prevalence of basic amino acids in their primary structures. Lysine-rich domains are found, for instance, in diatom silaffin proteins and in the sorghum grass siliplant protein. These domains exhibit catalytic activity in silica chain condensation, owing to molecular interactions of the lysine amine groups with the forming mineral. The use of amine chemistry by two very remote organisms has motivated us to seek other molecular biosilicification processes that may be common to the two life forms. In diatom silaffins, domains rich in phosphoserine residues are thought to assist the assembly of silaffin molecules into an organic supra-structure which serves as a template for the silica to precipitate on. This mold, held by salt bridges between serine phosphates and lysine amines, dictates the shape of the silica particles formed. Yet, silica synthesized with the dephosphorylated silaffin in phosphate buffer showed similar morphology to the one prepared with the native protein, suggesting that a defined spatial arrangement of serine phosphates is not required to generate silica with the desired shape. Concurrently, free phosphates enhanced the activity of siliplant1 in silica formation. It is therefore beneficial to characterize the involvement of these anions as co-factors in regulated silicification by functional peptides from the two proteins and to understand whether they play similar molecular role in the mechanism of mineralization. Here we analyze the molecular interactions of free phosphate ions with silica and the silaffin peptide PL12 and separately with silica and siliplant1 peptide SLP1 in the two biomimetic silica products generated by the two peptides. MAS NMR measurements show that the phosphate ions interact with the peptides and at the same time may be forming bonds with the silica mineral. This bridging capability may add another avenue by which the structure of the silica material is influenced. A model for the molecular/ionic interactions at the bio-inorganic interface is described, which may have bearings for the role of phosphorylated residues beyond the function as intermolecular cross linkers or free phosphate ions as co-factors in regulation of silicification.
Hodson, M. J. ; Song, Z. ; Ball, T. B. ; Elbaum, R. ; Struyf, E. Editorial: Frontiers in Phytolith Research. Frontiers in Plant Science 2020, 11, 454. Publisher's Version
Radhakrishnan, D. ; Shanmukhan, A. P. ; Kareem, A. ; Aiyaz, M. ; Varapparambathu, V. ; Toms, A. ; Kerstens, M. ; Valsakumar, D. ; Landge, A. N. ; Shaji, A. ; et al. A coherent feed forward loop drives vascular regeneration in damaged aerial organs growing in normal developmental-context. Development 2020.Abstract
Aerial organs of plants being highly prone to local injuries, require tissue restoration to ensure their survival. However, knowledge of the underlying mechanism is sparse. In this study, we mimicked natural injuries in growing leaf and stem to study the reunion between mechanically disconnected tissues. We show that ()/ () genes, which encodes stem cell promoting factors, are activated and contribute to vascular regeneration in response to these injuries. PLT proteins bind to and activate the CUC2 promoter. Both PLT and CUC2 regulate the transcription of the local auxin biosynthesis gene YUC4 in a coherent feed forward loop, and this process is necessary to drive vascular regeneration. In the absence of this PLT mediated regeneration response, leaf ground tissue cells can neither acquire early vascular identity marker ATHB8, nor properly polarize auxin transporters to specify new venation paths. The PLT-CUC2 module is required for vascular regeneration, but is dispensable for midvein formation in leaf. We reveal the mechanisms of vascular regeneration in plants and distinguishes the wound repair ability of the tissue from its formation during normal development.
Oren, E. ; Tzuri, G. ; Dafna, A. ; Meir, A. ; Kumar, R. ; Katzir, N. ; Elkind, Y. ; Freilich, S. ; Schaffer, A. A. ; Tadmor, Y. ; et al. High-density NGS-based map construction and genetic dissection of fruit shape and rind netting in Cucumis melo. Theor Appl Genet 2020.Abstract
Melon is an important crop that exhibits broad variation for fruit morphology traits that are the substrate for genetic mapping efforts. In the post-genomic era, the link between genetic maps and physical genome assemblies is key for leveraging QTL mapping results for gene cloning and breeding purposes. Here, using a population of 164 melon recombinant inbred lines (RILs) that were subjected to genotyping-by-sequencing, we constructed and compared high-density sequence- and linkage-based recombination maps that were aligned to the reference melon genome. These analyses reveal the genome-wide variation in recombination frequency and highlight regions of disrupted collinearity between our population and the reference genome. The population was phenotyped over 3 years for fruit size and shape as well as rind netting. Four QTLs were detected for fruit size, and they act in an additive manner, while significant epistatic interaction was found between two neutral loci for this trait. Fruit shape displayed transgressive segregation that was explained by the action of four QTLs, contributed by alleles from both parents. The complexity of rind netting was demonstrated on a collection of 177 diverse accessions. Further dissection of netting in our RILs population, which is derived from a cross of smooth and densely netted parents, confirmed the intricacy of this trait and the involvement of major locus and several other interacting QTLs. A major netting QTL on chromosome 2 co-localized with results from two additional populations, paving the way for future study toward identification of a causative gene for this trait.
Gorovits, R. ; Sobol, I. ; Akama, K. ; Chefetz, B. ; Czosnek, H. Pharmaceuticals in treated wastewater induce a stress response in tomato plants. Sci Rep 2020, 10, 1856.Abstract
Pharmaceuticals remain in treated wastewater used to irrigate agricultural crops. Their effect on terrestrial plants is practically unknown. Here we tested whether these compounds can be considered as plant stress inducers. Several features characterize the general stress response in plants: production of reactive oxygen species acting as stress-response signals, MAPKs signaling cascade inducing expression of defense genes, heat shock proteins preventing protein denaturation and degradation, and amino acids playing signaling roles and involved in osmoregulation. Tomato seedlings bathing in a cocktail of pharmaceuticals (Carbamazepine, Valporic acid, Phenytoin, Diazepam, Lamotrigine) or in Carbamazepine alone, at different concentrations and during different time-periods, were used to study the patterns of stress-related markers. The accumulation of the stress-related biomarkers in leaf and root tissues pointed to a cumulative stress response, mobilizing the cell protection machinery to avoid metabolic modifications and to restore homeostasis. The described approach is suitable for the investigation of stress response of different crop plants to various contaminants present in treated wastewater.
Glanz-Idan, N. ; Wolf, S. Upregulation of photosynthesis in mineral nutrition-deficient tomato plants by reduced source-to-sink ratio. Plant Signal Behav 2020, 15, 1712543.Abstract
Photosynthetic activity is affected by environmental factors and endogenous signals controlled by the source-sink relationship. We recently showed upregulated photosynthetic rate following partial defoliation under favorable environmental conditions. Here, we examined the influence of partial defoliation on the remaining leaves' function in tomato plants under nutrient deficiency. The effect of partial defoliation was more pronounced under limited mineral supply vs. favorable conditions. Reduced source-sink ratio resulted in increased stomatal conductance and transpiration rate, as well as higher photosystem II efficiency. Although chlorophyll concentration was significantly reduced under limited nutrient supply, the photosynthetic rate in the remaining leaf was similar to that measured under normal fertilization. Expression of genes involved in the phloem loading of assimilated sugars was downregulated in the remaining source leaf of unfertilized plants, 15 d after partial defoliation; in fertilized plants, these genes' expression was similar in control and partially defoliated plants. We propose that at early stage, the additional carbon assimilated in the remaining leaf is devoted to increasing source size rather than sink growth. The size increase of the remaining leaf in unfertilized plants was not sufficient to rebalance the source-sink ratio, resulting in inhibited sugar export and further carbohydrate allocation in the remaining leaf.
Glanz-Idan, N. ; Tarkowski, P. ; Turečková, V. ; Wolf, S. Root-shoot communication in tomato plants: cytokinin as a signal molecule modulating leaf photosynthetic activity. Journal of experimental botany 2020, 71, 247-257. Publisher's VersionAbstract
Photosynthetic activity is affected by exogenous and endogenous inputs, including source-sink balance. Reducing the source to sink ratio by partial defoliation or heavy shading resulted in significant elevation of the photosynthetic rate in the remaining leaf of tomato plants within 3 d. The remaining leaf turned deep green, and its area increased by almost 3-fold within 7 d. Analyses of photosynthetic activity established up-regulation due to increased carbon fixation activity in the remaining leaf, rather than due to altered water balance. Moreover, senescence of the remaining leaf was significantly inhibited. As expected, carbohydrate concentration was lower in the remaining leaf than in the control leaves; however, expression of genes involved in sucrose export was significantly lower. These results suggest that the accumulated fixed carbohydrates were primarily devoted to increasing the size of the remaining leaf. Detailed analyses of the cytokinin content indicated that partial defoliation alters cytokinin biosynthesis in the roots, resulting in a higher concentration of trans-zeatin riboside, the major xylem-translocated molecule, and a higher concentration of total cytokinin in the remaining leaf. Together, our findings suggest that trans-zeatin riboside acts as a signal molecule that traffics from the root to the remaining leaf to alter gene expression and elevate photosynthetic activity. © The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Experimental Biology.
Ohana-Levi, N. ; Munitz, S. ; Ben-Gal, A. ; Schwartz, A. ; Peeters, A. ; Netzer, Y. Multiseasonal grapevine water consumption – Drivers and forecasting. Agricultural and Forest Meteorology 2020, 280. Publisher's VersionAbstract
The interactions between temperature, relative humidity, radiation, wind speed and their effect on plant transpiration in the context of water consumption for irrigation purposes have been studied for over a century. Leaf area has also been established as an important factor affecting water consumption. We analyzed a multivariable time series composed of both meteorological and vegetative variables with a daily temporal resolution for the growing seasons of 2013–2016 for Vitis vinfera ‘Cabernet Sauvignon’ vineyards in the mountainous region in Israel. Time-series analysis of this data was used to characterize seasonal patterns affecting water consumption (ETc) of vines and to quantify interrelations between meteorological and vegetative factors affecting vine water consumption. Moreover, we applied a machine learning regression model to determine the relative influence of meteorological and vegetative factors on ETc during four growing seasons. Finally, we developed an ensemble model for temporally forecasting vine ETc for an additional season using a training dataset of multiple variables. Our findings show that decomposing the time-series dataset uncovered a wider variety of underlying temporal patterns, and enabled quantification of seasonal and daily relationships. Leaf area had a substantial impact on ETc and was found to have a relative influence ranging between 62 and 86% for the different growing seasons. Mean temperature was ranked second followed by minor effects of relative humidity, solar radiation and wind speed that were interchangeably ordered. The ensemble model produced reliable results, with cross validation coefficients   0.9. Incorporating leaf area measurements into the regression model improved both the performance of the model and the training data correlation. Using time-series statistics to explore meteorological and vegetative temporal characteristics, patterns, interrelations and relative effect on evapotranspiration may facilitate the understanding of water consumption processes and assist in generating more effective and skillful irrigation models. © 2019 Elsevier B.V.
2019
Ghosh, S. ; Kanakala, S. ; Lebedev, G. ; Kontsedalov, S. ; Silverman, D. ; Alon, T. ; Mor, N. ; Sela, N. ; Luria, N. ; Dombrovsky, A. ; et al. Transmission of a New Polerovirus Infecting Pepper by the Whitefly Bemisia tabaci. Journal of Virology 2019, 93. Publisher's VersionAbstract
Many animal and plant viruses depend on arthropods for their transmission. Virus-vector interactions are highly specific, and only one vector or one of a group of vectors from the same family is able to transmit a given virus. Poleroviruses (Luteoviridae) are phloem-restricted RNA plant viruses that are exclusively transmitted by aphids. Multiple aphid-transmitted polerovirus species commonly infect pepper, causing vein yellowing, leaf rolling, and fruit discoloration. Despite low aphid populations, a recent outbreak with such severe symptoms in many bell pepper farms in Israel led to reinvestigation of the disease and its insect vector. Here we report that this outbreak was caused by a new whitefly (Bemisia tabaci)-transmitted polerovirus, which we named Pepper whitefly-borne vein yellows virus (PeWBVYV). PeWBVYV is highly (>95%) homologous to Pepper vein yellows virus (PeVYV) from Israel and Greece on its 5' end half, while it is homologous to African eggplant yellows virus (AeYV) on its 3' half. Koch’s postulates were proven by constructing a PeWBVYV infectious clone causing the pepper disease, which was in turn transmitted to test pepper plants by B. tabaci but not by aphids. PeWBVYV represents the first report of a whitefly-transmitted polerovirus.IMPORTANCE The high specificity of virus-vector interactions limits the possibility of a given virus changing vectors. Our report describes a new virus from a family of viruses strictly transmitted by aphids which is now transmitted by whiteflies (Bemisia tabaci) and not by aphids. This report presents the first description of polerovirus transmission by whiteflies. Whiteflies are highly resistant to insecticides and disperse over long distances, carrying virus inoculum. Thus, the report of such unusual polerovirus transmission by a supervector has extensive implications for the epidemiology of the virus disease, with ramifications concerning the international trade of agricultural commodities.
Shorinola, O. ; Kaye, R. ; Golan, G. ; Peleg, Z. ; Kepinski, S. ; Uauy, C. Genetic Screening for Mutants with Altered Seminal Root Numbers in Hexaploid Wheat Using a High-Throughput Root Phenotyping Platform. G3 (Bethesda) 2019, 9 2799-2809.Abstract
Roots are the main channel for water and nutrient uptake in plants. Optimization of root architecture provides a viable strategy to improve nutrient and water uptake efficiency and maintain crop productivity under water-limiting and nutrient-poor conditions. We know little, however, about the genetic control of root development in wheat, a crop supplying 20% of global calorie and protein intake. To improve our understanding of the genetic control of seminal root development in wheat, we conducted a high-throughput screen for variation in seminal root number using an exome-sequenced mutant population derived from the hexaploid wheat cultivar Cadenza. The screen identified seven independent mutants with homozygous and stably altered seminal root number phenotypes. One mutant, Cadenza0900, displays a recessive extra seminal root number phenotype, while six mutants (Cadenza0062, Cadenza0369, Cadenza0393, Cadenza0465, Cadenza0818 and Cadenza1273) show lower seminal root number phenotypes most likely originating from defects in the formation and activation of seminal root primordia. Segregation analysis in F populations suggest that the phenotype of Cadenza0900 is controlled by multiple loci whereas the Cadenza0062 phenotype fits a 3:1 mutant:wild-type segregation ratio characteristic of dominant single gene action. This work highlights the potential to use the sequenced wheat mutant population as a forward genetic resource to uncover novel variation in agronomic traits, such as seminal root architecture.
Cárdenas, P. D. ; Sonawane, P. D. ; Heinig, U. ; Jozwiak, A. ; Panda, S. ; Abebie, B. ; Kazachkova, Y. ; Pliner, M. ; Unger, T. ; Wolf, D. ; et al. Pathways to defense metabolites and evading fruit bitterness in genus Solanum evolved through 2-oxoglutarate-dependent dioxygenases. Nat Commun 2019, 10, 5169.Abstract
The genus Solanum comprises three food crops (potato, tomato, and eggplant), which are consumed on daily basis worldwide and also producers of notorious anti-nutritional steroidal glycoalkaloids (SGAs). Hydroxylated SGAs (i.e. leptinines) serve as precursors for leptines that act as defenses against Colorado Potato Beetle (Leptinotarsa decemlineata Say), an important pest of potato worldwide. However, SGA hydroxylating enzymes remain unknown. Here, we discover that 2-OXOGLUTARATE-DEPENDENT-DIOXYGENASE (2-ODD) enzymes catalyze SGA-hydroxylation across various Solanum species. In contrast to cultivated potato, Solanum chacoense, a widespread wild potato species, has evolved a 2-ODD enzyme leading to the formation of leptinines. Furthermore, we find a related 2-ODD in tomato that catalyzes the hydroxylation of the bitter α-tomatine to hydroxytomatine, the first committed step in the chemical shift towards downstream ripening-associated non-bitter SGAs (e.g. esculeoside A). This 2-ODD enzyme prevents bitterness in ripe tomato fruit consumed today which otherwise would remain unpleasant in taste and more toxic.
Zancajo, V. M. R. ; Diehn, S. ; Filiba, N. ; Goobes, G. ; Kneipp, J. ; Elbaum, R. Spectroscopic Discrimination of Sorghum Silica Phytoliths. Front Plant Sci 2019, 10, 1571.Abstract
Grasses accumulate silicon in the form of silicic acid, which is precipitated as amorphous silica in microscopic particles termed phytoliths. These particles comprise a variety of morphologies according to the cell type in which the silica was deposited. Despite the evident morphological differences, phytolith chemistry has mostly been analysed in bulk samples, neglecting differences between the varied types formed in the same species. In this work, we extracted leaf phytoliths from mature plants of (L.) Moench. Using solid state NMR and thermogravimetric analysis, we show that the extraction methods alter greatly the silica molecular structure, its condensation degree and the trapped organic matter. Measurements of individual phytoliths by Raman and synchrotron FTIR microspectroscopies in combination with multivariate analysis separated bilobate silica cells from prickles and long cells, based on the silica molecular structures and the fraction and composition of occluded organic matter. The variations in structure and composition of sorghum phytoliths suggest that the biological pathways leading to silica deposition vary between these cell types.
Mugabe, D. ; Coyne, C. J. ; Piaskowski, J. ; Zheng, P. ; Ma, Y. ; Landry, E. ; McGee, R. ; Main, D. ; Vandemark, G. ; Zhang, H. ; et al. Quantitative trait loci for cold tolerance in Chickpea. Crop Science 2019, 59, 573-582. Publisher's VersionAbstract
Fall-sown chickpea (Cicer arietinum L.) yields are often double those of spring-sown chickpea in regions with Mediterranean climates that have mild winters. However, winter kill can limit the productivity of fall-sown chickpea. Developing cold-tolerant chickpea would allow the expansion of the current geographic range where chickpea is grown and also improve productivity. The objective of this study was to identify the quantitative trait loci (QTL) associated with cold tolerance in chickpea. An interspecific recombinant inbred line population of 129 lines derived from a cross between ICC 4958, a cold-sensitive desi type (C. arietinum), and PI 489777, a coldtolerant wild relative (C. reticulatum Ladiz), was used in this study. The population was phenotyped for cold tolerance in the field over four field seasons (September 2011-March 2015) and under controlled conditions two times. The population was genotyped using genotypingby- sequencing, and an interspecific genetic linkage map consisting of 747 single nucleotide polymorphism (SNP) markers, spanning a distance of 393.7 cM, was developed. Three significant QTL were found on linkage groups (LGs) 1B, 3, and 8. The QTL on LGs 3 and 8 were consistently detected in six environments with logarithm of odds score ranges of 5.16 to 15.11 and 5.68 to 23.96, respectively. The QTL CT Ca-3.1 explained 7.15 to 34.6% of the phenotypic variance in all environments, whereas QTL CT Ca-8.1 explained 11.5 to 48.4%. The QTLassociated SNP markers may become useful for breeding with further fine mapping for increasing cold tolerance in domestic chickpea. © Crop Science Society of America.
Mello, A. ; Efroni, I. ; Rahni, R. ; Birnbaum, K. D. The Selaginella rhizophore has a unique transcriptional identity compared with root and shoot meristems. New Phytologist 2019, 222, 882-894. Publisher's VersionAbstract
The genus Selaginella resides in an early branch of the land plant lineage that possesses a vasculature and roots. The majority of the Selaginella root system is shoot borne and emerges through a distinctive structure known as the rhizophore, the organ identity of which has been a long-debated question. The rhizophore of Selaginella moellendorffii – a model for the lycophytes – shows plasticity to develop into a root or shoot up until 8 d after angle meristem emergence, after which it is committed to root fate. We subsequently use morphology and plasticity to define the stage of rhizophore identity. Transcriptomic analysis of the rhizophore during its plastic stage reveals that, despite some resemblance to the root meristem, rhizophore gene expression patterns are largely distinct from both shoot and root meristems. Based on this transcriptomic analysis and on historical anatomical work, we conclude that the rhizophore is a distinct organ with unique features. © 2019, Blackwell Publishing Ltd. All rights reserved.
Nissan, H. ; Blum, S. ; Shimoni, E. ; Elbaum, R. Characterization of Silicon Accumulation in Maize Cell Suspension Cultures. Silicon 2019, 11, 2377-2383. Publisher's VersionAbstract
Purpose: Silicon (Si) is an abundant element in the earth’s crust and is available to plants as silicic acid. Silicon uptake by plants is correlated with increased tolerance to various biotic and abiotic stresses. However, cellular mechanisms responsible for its beneficial effects are still unknown. Even its cellular import mechanisms are not well understood. We thus aimed to characterize silicon localization within minimally differentiated Zea mays (Black Mexican Sweet) cells in suspension. Methods: Cells were grown in a medium containing silicon, and the mRNA levels of silicon transporters were measured by real-time PCR. Cells were separated into an insoluble (mainly walls and starch) and a cytoplasmic fraction. Soluble and total silicon was measured by inductively-coupled-plasma – atomic-emission-spectroscopy. Silicon distribution was assessed by transmission electron microscopy. The cell walls were analyzed chemically, and by Raman micro-spectroscopy and thermal gravimetric analysis. Results: Silicon treatment reduced the levels of silicon transporters transcripts, without affecting cell proliferation. About 70 % of the silicon was localized in the cytoplasm, mostly in vesicles. We found indications that silicon affected the secondary structure of proteins and thermally stabilized starch. Silicon was loosely bound, and diffused out of the cells within 24 hours. Conclusions: Our results show that silicon binds spontaneously to cell walls/starch and accumulates in cytoplasm vesicles. These processes allow the cells to accumulate silicon against its concentration gradient in solution. However, cellular intake acts against reversible diffusion processes, probably through the aquaporin silicon channels (Lsi1, Lsi6) that exchange the cellular silicon with the surrounding medium. © 2015, Springer Science+Business Media Dordrecht.
Gabay, G. ; Faigenboim, A. ; Dahan, Y. ; Izhaki, Y. ; Itkin, M. ; Malitsky, S. ; Elkind, Y. ; Flaishman, M. A. Transcriptome analysis and metabolic profiling reveal the key role of α-linolenic acid in dormancy regulation of European pear. Journal of Experimental Botany 2019, 70, 734-737. Publisher's VersionAbstract
Deciduous trees require sufficient chilling during winter dormancy to grow. To decipher the dormancy-regulating mechanism, we carried out RNA sequencing (RNA-Seq) analysis and metabolic profiling of European pear (Pyrus communis L.) vegetative buds during the dormancy phases. Samples were collected from two cultivars that differed greatly in their chilling requirements: Spadona' (SPD), a low chilling requirement cultivar; and Harrow Sweet (HS), a high chilling requirement cultivar. Comparative transcriptome analysis revealed >8500 differentially expressed transcripts; most were related to metabolic pathways. Out of 174 metabolites, 44 displayed differential levels in both cultivars, 38 were significantly changed only in SPD, and 15 only in HS. Phospholipids were mostly accumulated at the beginning of dormancy, sugars between before dormancy and mid-dormancy, and fatty acids, including α-linolenic acid, at dormancy break. Differentially expressed genes underlying previously identified major quantitative trait loci (QTLs) in linkage group 8 included genes related to the α-linolenic acid pathway, 12-oxophytodienoate reductase 2-like, and the DORMANCY-ASSOCIATED MADS-BOX (DAM) genes, PcDAM1 and PcDAM2, putative orthologs of PpDAM1 and PpDAM2, confirming their role for the first time in European pear. Additional new putative dormancy-related uncharacterized genes and genes related to metabolic pathways are suggested. These results suggest the crucial role of α-linolenic acid and DAM genes in pear bud dormancy phase transitions. © 2018 The Author(s).
Bahat, I. ; Netzer, Y. ; Ben-Gal, A. ; Grünzweig, J. ; Peeters, A. ; Cohen, Y. Comparison of water potential and yield parameters under uniform and variable rate drip irrigation in a cabernet sauvignon vineyard. In Precision Agriculture 2019 - Papers Presented at the 12th European Conference on Precision Agriculture, ECPA 2019; Precision Agriculture 2019 - Papers Presented at the 12th European Conference on Precision Agriculture, ECPA 2019; 2019; pp. 125-131. Publisher's VersionAbstract
An experiment in variable-rate drip irrigation (VRDI) was aimed at reducing variance of midday stem water potential (SWP) and in yield parameters by applying VRDI in a highly variable vineyard. During 2018, irrigation was separated into VRDI and uniform irrigation (UI) blocks. Each block was delineated to 10 management cells, and results of 2018 season were compared to 2017 season under UI. Standard error (SE) of SWP in the last 3 measurements before harvest decreased in the VRDI block in 2018 compared to 2017 by 14-44%. In contrast, in the UI block, SE in 2018 was higher by 11-42% compared to 2017. SE of fruit yield showed a similar trend. Applying principles of precision irrigation may lead to a more homogeneous vineyard in the parameters described above and to improved wine quality. © Wageningen Academic Publishers 2019