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Steiner, E. ; Triana, M. R. ; Kubasi, S. ; Blum, S. ; Paz-Ares, J. ; Rubio, V. ; Weiss, D. KISS ME DEADLY F-box proteins modulate cytokinin responses by targeting the transcription factor TCP14 for degradation. Plant Physiol 2021. Abstract
Dear Editor,TCPs are basic helix-loop-helix transcription factors. Arabidopsis (Arabidopsis thaliana) has 24 TCPs, 13 belong to Class I, and 11 to Class II (Martín-Trillo and Cubas, 2010). Class I TCPs promote, and Class II restrict, cell proliferation (Efroni et al., 2008). Previously, we showed that two Class I TCPs, TCP14 and TCP15 interact with the O-fucosyltransferase (OFT) SPINDLY (SPY) to promote cytokinin (CK) responses in young leaves and flowers (Steiner et al., 2012). SPY activity is required for TCP14 stability; the loss of SPY stimulates TCP14 proteolysis by the 26S proteasome and inhibits CK responses in flowers and leaves (Steiner et al., 2016). This is reversed by mutation in CULLIN1 (CUL1), suggesting a role for Skp, CUL1, F-box E3 ubiquitin ligase (SCF) complex in TCP14 proteolysis. OFT modify target proteins by transferring mono-fucose to serine and threonine residues (Holdener and Haltiwanger, 2019). SPY modifies the DELLA protein REPRESSOR OF ga1-3 (RGA) and increases its activity (Zentella et al., 2017). SPY also modifies PSEUDO RESPONSE REGULATOR5 (PRR5) and facilitates its proteolysis (Wang et al., 2020). Since mutation in the putative OFT catalytic domain of SPY (spy-3) is sufficient to reduce TCP14 stability, we suggested that O-fucosylation by SPY stabilizes TCP14. Here, we bring evidence that TCP14 interacts with the F-box proteins KISS ME DEADLY1 (KMD1), KMD2, and KMD4 (Kim et al., 2013) and this interaction promotes its degradation in the spy background. KMDs are negative regulators of CK signaling; they interact and destabilize the CK signaling components Type B RESPONSE REGULATOR (RR). Zhang et al. (2013) found that KMDs also target PHENYLALANINE AMMONIA LYASE (PAL) for degradation. Thus, although F-box proteins have high substrate specificity, KMDs seem to target several unrelated proteins.
Fatiukha, A. ; Deblieck, M. ; Klymiuk, V. ; Merchuk-Ovnat, L. ; Peleg, Z. ; Ordon, F. ; Fahima, T. ; Korol, A. ; Saranga, Y. ; Krugman, T. Genomic Architecture of Phenotypic Plasticity in Response to Water Stress in Tetraploid Wheat. International journal of molecular sciences 2021, 22, 1723. Abstract
Phenotypic plasticity is one of the main mechanisms of adaptation to abiotic stresses via changes in critical developmental stages. Altering flowering phenology is a key evolutionary strategy of plant adaptation to abiotic stresses, to achieve the maximum possible reproduction. The current study is the first to apply the linear regression residuals as drought plasticity scores while considering the variation in flowering phenology and traits under non-stress conditions. We characterized the genomic architecture of 17 complex traits and their drought plasticity scores for quantitative trait loci (QTL) mapping, using a mapping population derived from a cross between durum wheat (Triticum turgidum ssp. durum) and wild emmer wheat (T. turgidum ssp. dicoccoides). We identified 79 QTLs affected observed traits and their plasticity scores, of which 33 reflected plasticity in response to water stress and exhibited epistatic interactions and/or pleiotropy between the observed and plasticity traits. Vrn-B3 (TaTF1) residing within an interval of a major drought-escape QTL was proposed as a candidate gene. The favorable alleles for most of the plasticity QTLs were contributed by wild emmer wheat, demonstrating its high potential for wheat improvement. Our study presents a new approach for the quantification of plant adaptation to various stresses and provides new insights into the genetic basis of wheat complex traits under water-deficit stress.
Firsov, A. ; Shaloiko, L. ; Kozlov, O. ; Vainstein, A. ; Dolgov, S. Tomatoes expressing thaumatin II retain their sweet taste after salting and pickling processing. Journal of the Science of Food and AgricultureJournal of the Science of Food and AgricultureJ Sci Food Agric 2021, n/a. Abstract
Abstract BACKGROUND Thaumatin II, a supersweet protein from the African plant katemfe (Thaumatococcus daniellii Benth.), shows promise as a zero-calorie sweetener for use in the food and pharmaceutical industries and for improving the taste of fruit. RESULTS We report on the stability of thaumatin in salted and pickled tomatoes, as well as on the effect of thaumatin on the taste quality of processed tomatoes. Fruit of tomato cv. Yalf, transformed with the thaumatin II gene were salted and pickled and then stored for 6 months. Western blot analysis showed relative thaumatin II stability at salting; its content in processed fruits was 62?83% of the initial level depending in the studied line. In pickled tomatoes, thaumatin II content was decreased by up to 25% of the initial amount. Both salted and pickled tomatoes had a sweet taste with a typical thaumatin aftertaste. Salted tomatoes were characterized as being sweeter than pickled tomatoes. The overall taste of pickled tomatoes was rated by panellists as significantly better compared to that of salted or non-processed ones. CONCLUSION In the present study, we have shown that tomatoes expressing supersweet protein thaumatin II can be used for processing under mild conditions, including salting and pickling. ? 2021 Society of Chemical Industry.
Hendel, E. ; Bacher, H. ; Oksenberg, A. ; Walia, H. ; Schwartz, N. ; Peleg, Z. Deciphering the genetic basis of wheat seminal root anatomy uncovers ancestral axial conductance alleles. Plant, Cell & Environment 2021, n/a. Abstract
ABSTRACT Root axial conductance which describes the ability of water to move through the xylem, contributes to the rate of water uptake from the soil throughout the whole plant lifecycle. Under the rainfed wheat agro-system, grain-filling is typically occurring during declining water availability (i.e. terminal drought). Therefore, preserving soil water moisture during grain filling could serve as a key adaptive trait. We hypothesized that lower wheat root axial conductance can promote higher yields under terminal drought. A segregating population derived from a cross between durum wheat and its direct progenitor wild emmer wheat was used to underpin the genetic basis of seminal root architectural and functional traits. We detected 75 QTL associated with seminal roots morphological, anatomical, and physiological traits, with several hotspots harboring co-localized QTL. We further validated the axial conductance and central metaxylem QTL using wild introgression lines. Field-based characterization of genotypes with contrasting axial conductance suggested the contribution of low axial conductance as a mechanism for water conservation during grain filling and consequent increase in grain size and yield. Our findings underscore the potential of harnessing wild alleles to reshape the wheat root system architecture and associated hydraulic properties for greater adaptability under changing climate. This article is protected by copyright. All rights reserved.
Hendelman, A. ; Zebell, S. ; Rodriguez-Leal, D. ; Dukler, N. ; Robitaille, G. ; Wu, X. ; Kostyun, J. ; Tal, L. ; Wang, P. ; Bartlett, M. E. ; et al. Conserved pleiotropy of an ancient plant homeobox gene uncovered by cis-regulatory dissection. 2021. Abstract
SummaryDivergence of gene function is a hallmark of evolution, but assessing functional divergence over deep time is not trivial. The few alleles available for cross-species studies often fail to expose the entire functional spectrum of genes, potentially obscuring deeply conserved pleiotropic roles. Here, we explore the functional divergence of WUSCHEL HOMEOBOX9 (WOX9), suggested to have species-specific roles in embryo and inflorescence development. Using a cis-regulatory editing drive system, we generate a comprehensive allelic series in tomato, which revealed hidden pleiotropic roles for WOX9. Analysis of accessible chromatin and conserved cis-regulatory sequences identifies the regions responsible for this pleiotropic activity, the functions of which are conserved in groundcherry, a tomato relative. Mimicking these alleles in Arabidopsis, distantly related to tomato and groundcherry, reveals new inflorescence phenotypes, exposing a deeply conserved pleiotropy. We suggest that targeted cis-regulatory mutations can uncover conserved gene functions and reduce undesirable effects in crop improvement.
Ramon, U. ; Weiss, D. ; Illouz-Eliaz, N. Underground gibberellin activity: differential gibberellin response in tomato shoots and roots. New PhytologistNew PhytologistNew Phytol 2021, 229, 1196 - 1200.
Steiner, E. ; Triana, M. R. ; Kubasi, S. ; Blum, S. ; Paz-Ares, J. ; Rubio, V. ; Weiss, D. KISS ME DEADLY F-box proteins modulate cytokinin responses by targeting the transcription factor TCP14 for degradation. Plant Physiol 2021.
Weksler, S. ; Rozenstein, O. ; Haish, N. ; Moshelion, M. ; Wallach, R. ; Ben-Dor, E. Detection of Potassium Deficiency and Momentary Transpiration Rate Estimation at Early Growth Stages Using Proximal Hyperspectral Imaging and Extreme Gradient Boosting. Sensors 2021, 21. Abstract
{Potassium is a macro element in plants that is typically supplied to crops in excess throughout the season to avoid a deficit leading to reduced crop yield. Transpiration rate is a momentary physiological attribute that is indicative of soil water content, the plant’s water requirements, and abiotic stress factors. In this study, two systems were combined to create a hyperspectral–physiological plant database for classification of potassium treatments (low, medium, and high) and estimation of momentary transpiration rate from hyperspectral images. PlantArray 3.0 was used to control fertigation, log ambient conditions, and calculate transpiration rates. In addition, a semi-automated platform carrying a hyperspectral camera was triggered every hour to capture images of a large array of pepper plants. The combined attributes and spectral information on an hourly basis were used to classify plants into their given potassium treatments (average accuracy = 80%) and to estimate transpiration rate (RMSE = 0.025 g/min
Aharon, S. ; Fadida-Myers, A. ; Nashef, K. ; Ben-David, R. ; Lati, R. N. ; Peleg, Z. Genetic improvement of wheat early vigor promote weed-competitiveness under Mediterranean climate. 2021, 303, 110785. Abstract
Chemical weed-control is the most effective practice for wheat, however, rapid evolution of herbicide-resistant weeds threat food-security and calls for integration of non-chemical practices. We hypothesis that integration of alternative GA-responsive dwarfing genes into elite wheat cultivars can promote early vigor and weed-competitiveness under Mediterranean climate. We develop near-isogenic lines of bread wheat cultivars with GAR dwarfing genes and evaluate them for early vigor and weed-competitiveness under various environmental and management conditions to identify promising NIL for weed-competitiveness and grain yield. While all seven NILs responded to external gibberellic acid application, they exhibited differences in early vigor. Greenhouse and field evaluations highlighted NIL OC1 (Rht8andRht12) as a promising line, with significant advantage in canopy early vigor over its parental. To facilitate accurate and continuous early vigor data collection, we applied non-destructive image-based phenotyping approaches which offers non-expensive and end-user friendly solution for selection. NIL OC1 was tested under different weed density level, infestation waves, and temperatures and highlight the complex genotypic × environmental × management interactions. Our findings demonstrate the potential of genetic modification of dwarfing genes as promising approach to improve weed-competitiveness, and serve as basis for future breeding efforts to support sustainable wheat production under semi-arid Mediterranean climate.
Ben Shalom, T. ; Belsey, S. ; Chasnitsky, M. ; Shoseyov, O. Cellulose Nanocrystals and Corn Zein Oxygen and Water Vapor Barrier Biocomposite Films. Nanomaterials 2021, 11. Abstract
Cellulose nanocrystals (CNC) are well-suited to the preparation of biocomposite films and packaging material due to its abundance, renewability, biodegradability, and favorable film-forming capacity. In this study, different CNC and corn zein (CZ) composite films were prepared by adding CZ to the CNC suspension prior to drying, in order to change internal structure of resulting films. Films were developed to examine their performance as an alternative water vapor and oxygen-barrier for flexible packaging industry. Water vapor permeability (WVP) and oxygen transmission rate (OTR) of the biocomposite films decreased significantly in a specific ratio between CNC and CZ combined with 1,2,3,4-butane tetracarboxylic acid (BTCA), a nontoxic cross linker. In addition to the improved barrier properties, the incorporation of CZ benefitted the flexibility and thermal stability of the CNC/CZ composite films. The toughness increased by 358%, and Young’s modulus decreased by 32% compared with the pristine CNC film. The maximum degradation temperature increased by 26 °C, compared with that of CNC film. These results can be attributed to the incorporation of a hydrophobic protein into the matrix creating hydrophobic interactions among the biocomposite components. SEM and AFM analysis indicated that CZ could significantly affect the CNC arrangement, and the film surface topography, due to the mechanical bundling and physical adsorption effect of CZ to CNC. The presented results indicate that CNC/CZ biocomposite films may find applications in packaging, and in multi-functionalization materials.
Shumeiko, V. ; Paltiel, Y. ; Bisker, G. ; Hayouka, Z. ; Shoseyov, O. A nanoscale paper-based near-infrared optical nose (NIRON). Biosensors and Bioelectronics 2021, 172, 112763. Abstract
Electronic noses (e-nose) and optical noses (o-nose) are two emerging approaches for the development of artificial olfactory systems for flavor and smell evaluation. The current work leverages the unique optical properties of semiconducting single-wall carbon nanotubes (SWCNTs) to develop a prototype of a novel paper-based near-infrared optical nose (NIRON). We have drop-dried an array of SWCNTs encapsulated with a wide variety of peptides on a paper substrate and continuously imaged the emitted SWCNTs fluorescence using a CMOS camera. Odors and different volatile molecules were passed above the array in a flow chamber, resulting in unique modulation patterns of the SWCNT photoluminescence (PL). Quartz crystal microbalance (QCM) measurements performed in parallel confirmed the direct binding between the vapor molecules and the peptide-SWCNTs. PL levels measured before and during exposure demonstrate distinct responses to the four tested alcoholic vapors (ethanol, methanol, propanol, and isopropanol). In addition, machine learning tools directly applied to the fluorescence images allow us to distinguish between the aromas of red wine, beer, and vodka. Further, we show that the developed sensor can detect limonene, undecanal, and geraniol vapors, and differentiate between their smells utilizing the PL response pattern. This novel paper-based optical biosensor provides data in real-time, and is recoverable and suitable for working at room temperature and in a wide range of humidity levels. This platform opens new avenues for real-time sensing of volatile chemical compounds, odors, and flavors.
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. 2020, 133, 1927 - 1945. 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.
Hellwig, T. ; Flor, A. ; Saranga, Y. ; Coyne, C. J. ; Main, D. ; Sherman, A. ; Ophir, R. ; Abbo, S. Environmental and genetic determinants of amphicarpy in Pisum fulvum, a wild relative of domesticated pea. 2020, 298, 110566. Abstract
Pisum fulvum is an annual legume native to Syria, Lebanon, Israel and Jordan. In certain locations, P. fulvum individuals were documented to display a reproductive dimorphism – amphicarpy, with both above and below ground flowers and pods. Herein we aimed to study the possible role of soil texture on amphicarpy in P. fulvum, to investigate the possible bio-climatic associations of P. fulvum amphicarpy and to identify genetic markers associated with this phenotype. A set of 127 germplasm accessions sampled across the Israeli distribution range of the species was phenotyped in two common garden nurseries. Land use and bioclimatic data were used to delineate the eco-geographic clustering of accession's sampling sites. Single nucleotide polymorphism (SNP) markers were employed in genome-wide association study to identify associated loci. Amphicarpy was subject to strong experimental site x genotype interaction with higher phenotypic expression in fine textured soil relative to sandy loam. Amphicarpy was more prevalent among accessions sampled in eastern Judea and Samaria and was weakly associated with early phenology and relatively modest above ground biomass production. Twelve SNP markers were significantly associated with amphicarpy, each explaining between 8 and 12 % of the phenotypic variation. In P. fulvum amphicarpy seems to be a polygenetic trait controlled by an array of genes that is likely to be affected by environmental stimuli. The probable selective advantage of the association between amphicarpy and early flowering is in line with its relative prevalence in drought prone territories subject to heavy grazing.
Zancajo, V. M. R. ; Lindtner, T. ; Eisele, M. ; Huber, A. J. ; Elbaum, R. ; Kneipp, J. FTIR Nanospectroscopy Shows Molecular Structures of Plant Biominerals and Cell Walls. Analytical ChemistryAnalytical Chemistry 2020, 92, 13694 - 13701. Abstract
Plant tissues are complex composite structures of organic and inorganic components whose function relies on molecular heterogeneity at the nanometer scale. Scattering-type near-field optical microscopy (s-SNOM) in the mid-infrared (IR) region is used here to collect IR nanospectra from both fixed and native plant samples. We compared structures of chemically extracted silica bodies (phytoliths) to silicified and nonsilicified cell walls prepared as a flat block of epoxy-embedded awns of wheat (Triticum turgidum), thin sections of native epidermis cells from sorghum (Sorghum bicolor) comprising silica phytoliths, and isolated cells from awns of oats (Avena sterilis). The correlation of the scanning-probe IR images and the mechanical phase image enables a combined probing of mechanical material properties together with the chemical composition and structure of both the cell walls and the phytolith structures. The data reveal a structural heterogeneity of the different silica bodies in situ, as well as different compositions and crystallinities of cell wall components. In conclusion, IR nanospectroscopy is suggested as an ideal tool for studies of native plant materials of varied origins and preparations and could be applied to other inorganic–organic hybrid materials.Plant tissues are complex composite structures of organic and inorganic components whose function relies on molecular heterogeneity at the nanometer scale. Scattering-type near-field optical microscopy (s-SNOM) in the mid-infrared (IR) region is used here to collect IR nanospectra from both fixed and native plant samples. We compared structures of chemically extracted silica bodies (phytoliths) to silicified and nonsilicified cell walls prepared as a flat block of epoxy-embedded awns of wheat (Triticum turgidum), thin sections of native epidermis cells from sorghum (Sorghum bicolor) comprising silica phytoliths, and isolated cells from awns of oats (Avena sterilis). The correlation of the scanning-probe IR images and the mechanical phase image enables a combined probing of mechanical material properties together with the chemical composition and structure of both the cell walls and the phytolith structures. The data reveal a structural heterogeneity of the different silica bodies in situ, as well as different compositions and crystallinities of cell wall components. In conclusion, IR nanospectroscopy is suggested as an ideal tool for studies of native plant materials of varied origins and preparations and could be applied to other inorganic–organic hybrid materials.
Illouz-Eliaz, N. ; Nissan, I. ; Nir, I. ; Ramon, U. ; Shohat, H. ; Weiss, D. Mutations in the tomato gibberellin receptors suppress xylem proliferation and reduce water loss under water-deficit conditions. J Exp Bot 2020, 71, 3603 - 3612. Abstract
Low gibberellin (GA) activity in tomato (Solanum lycopersicum) inhibits leaf expansion and reduces stomatal conductance. This leads to lower transpiration and improved water status under transient drought conditions. Tomato has three GIBBERELLIN-INSENSITIVE DWARF1 (GID1) GA receptors with overlapping activities and high redundancy. We tested whether mutation in a single GID1 reduces transpiration without affecting growth and productivity. CRISPR-Cas9 gid1 mutants were able to maintain higher leaf water content under water-deficit conditions. Moreover, while gid1a exhibited normal growth, it showed reduced whole-plant transpiration and better recovery from dehydration. Mutation in GID1a inhibited xylem vessel proliferation, which led to lower hydraulic conductance. In stronger GA mutants, we also found reduced xylem vessel expansion. These results suggest that low GA activity affects transpiration by multiple mechanisms: it reduces leaf area, promotes stomatal closure, and reduces xylem proliferation and expansion, and as a result, xylem hydraulic conductance. We further examined if gid1a performs better than the control M82 in the field. Under these conditions, the high redundancy of GID1s was lost and gid1a plants were semi-dwarf, but their productivity was not affected. Although gid1a did not perform better under drought conditions in the field, it exhibited a higher harvest index.
Shohat, H. ; Illouz-Eliaz, N. ; Kanno, Y. ; Seo, M. ; Weiss, D. The Tomato DELLA Protein PROCERA Promotes Abscisic Acid Responses in Guard Cells by Upregulating an Abscisic Acid Transporter. Plant Physiology 2020, 184, 518. Abstract
Plants reduce transpiration through stomatal closure to avoid drought stress. While abscisic acid (ABA) has a central role in the regulation of stomatal closure under water-deficit conditions, we demonstrated in tomato (Solanum lycopersicum) that a gibberellin response inhibitor, the DELLA protein PROCERA (PRO), promotes ABA-induced stomatal closure and gene transcription in guard cells. To study how PRO affects stomatal closure, we performed RNA-sequencing analysis of isolated guard cells and identified the ABA transporters ABA-IMPORTING TRANSPORTER1.1 (AIT1.1) and AIT1.2, also called NITRATE TRANSPORTER1/PTR TRANSPORTER FAMILY4.6 in Arabidopsis (Arabidopsis thaliana), as being upregulated by PRO. Tomato has four AIT1 genes, but only AIT1.1 and AIT1.2 were upregulated by PRO, and only AIT1.1 exhibited high expression in guard cells. Functional analysis of AIT1.1 in yeast (Saccharomyces cerevisiae) confirmed its activity as an ABA transporter, possibly an importer. A clustered regularly interspaced short palindromic repeats-Cas9–derived ait1.1 mutant exhibited an increased transpiration, a larger stomatal aperture, and a reduced stomatal response to ABA. Moreover, ait1.1 suppressed the promoting effects of PRO on ABA-induced stomatal closure and gene expression in guard cells, suggesting that the effects of PRO on stomatal aperture and transpiration are AIT1.1-dependent. Previous studies suggest a negative crosstalk between gibberellin and ABA that is mediated by changes in hormone biosynthesis and signaling. The results of this study suggest this crosstalk is also mediated by changes in hormone transport.
Biru, F. N. ; Cazzonelli, C. I. ; Elbaum, R. ; Johnson, S. N. Contrasting effects of Miocene and Anthropocene levels of atmospheric CO2 on silicon accumulation in a model grass. Biology Letters 2020, 16, 20200608. Abstract
Grasses are hyper-accumulators of silicon (Si), which they acquire from the soil and deposit in tissues to resist environmental stresses. Given the high metabolic costs of herbivore defensive chemicals and structural constituents (e.g. cellulose), grasses may substitute Si for these components when carbon is limited. Indeed, high Si uptake grasses evolved in the Miocene when atmospheric CO2 concentration was much lower than present levels. It is, however, unknown how pre-industrial CO2 concentrations affect Si accumulation in grasses. Using Brachypodium distachyon, we hydroponically manipulated Si-supply (0.0, 0.5, 1, 1.5, 2 mM) and grew plants under Miocene (200 ppm) and Anthropocene levels of CO2 comprising ambient (410 ppm) and elevated (640 ppm) CO2 concentrations. We showed that regardless of Si treatments, the Miocene CO2 levels increased foliar Si concentrations by 47% and 56% relative to plants grown under ambient and elevated CO2, respectively. This is owing to higher accumulation overall, but also the reallocation of Si from the roots into the shoots. Our results suggest that grasses may accumulate high Si concentrations in foliage when carbon is less available (i.e. pre-industrial CO2 levels) but this is likely to decline under future climate change scenarios, potentially leaving grasses more susceptible to environmental stresses.
Sade, N. ; Peleg, Z. Future challenges for global food security under climate change. Food Security under Climate Change 2020, 295, 110467.
Glanz-Idan, N. ; Wolf, S. Upregulation of photosynthesis in mineral nutrition-deficient tomato plants by reduced source-to-sink ratio. Plant Signaling & BehaviorPlant Signaling & Behavior 2020, 15, 1712543. Abstract
ABSTRACTPhotosynthetic 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.
Attia, Z. ; Dalal, A. ; Moshelion, M. Vascular bundle sheath and mesophyll cells modulate leaf water balance in response to chitin. The Plant JournalThe Plant JournalPlant J 2020, 101, 1368 - 1377. Abstract
Summary Plants can detect pathogen invasion by sensing microbe-associated molecular patterns (MAMPs). This sensing process leads to the induction of defense responses. Numerous MAMP mechanisms of action have been described in and outside the guard cells. Here, we describe the effects of chitin, a MAMP found in fungal cell walls and insects, on the cellular osmotic water permeability (Pf) of the leaf vascular bundle-sheath (BS) and mesophyll cells (MCs), and its subsequent effect on leaf hydraulic conductance (Kleaf). BS is a parenchymatic tissue that tightly encases the vascular system. BS cells (BSCs) have been shown to influence Kleaf through changes in their Pf, for example, after sensing the abiotic stress response-regulating hormone abscisic acid. It was recently reported that, in Arabidopsis, the chitin receptors-like kinases, chitin elicitor receptor kinase 1 (CERK1) and LYSINE MOTIF RECEPTOR KINASE 5 (LYK5) are highly expressed in the BS as well as the neighboring mesophyll. Therefore, we studied the possible impact of chitin on these cells. Our results revealed that BSCs and MCs exhibit a sharp decrease in Pf in response to chitin treatment. In addition, xylem-fed chitin decreased Kleaf and led to stomatal closure. However, Atlyk5 mutant showed none of these responses. Complementing AtLYK5 in the BSCs (using the SCARECROW promoter) resulted in the response to chitin that was similar to that observed in the wild-type. These results suggest that BS play a role in the perception of apoplastic chitin and in initiating chitin-triggered immunity.