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The Robert H. Smith Institute of
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in Agriculture
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Publications

2020
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. Publisher's VersionAbstract
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. Publisher's VersionAbstract
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. Publisher's VersionAbstract
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. Publisher's Version
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. Publisher's VersionAbstract
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. Publisher's VersionAbstract
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.
Fatiukha, A. ; Klymiuk, V. ; Peleg, Z. ; Saranga, Y. ; Cakmak, I. ; Krugman, T. ; Korol, A. B. ; Fahima, T. Variation in phosphorus and sulfur content shapes the genetic architecture and phenotypic associations within the wheat grain ionome. The Plant JournalThe Plant JournalPlant J 2020, 101, 555 - 572. Publisher's VersionAbstract
Summary Dissection of the genetic basis of wheat ionome is crucial for understanding the physiological and biochemical processes underlying mineral accumulation in seeds, as well as for efficient crop breeding. Most of the elements essential for plants are metals stored in seeds as chelate complexes with phytic acid or sulfur-containing compounds. We assume that the involvement of phosphorus and sulfur in metal chelation is the reason for strong phenotypic correlations within ionome. Adjustment of element concentrations for the effect of variation in phosphorus and sulfur seed content resulted in drastic change of phenotypic correlations between the elements. The genetic architecture of wheat grain ionome was characterized by quantitative trait loci (QTL) analysis using a cross between durum and wild emmer wheat. QTL analysis of the adjusted traits and two-trait analysis of the initial traits paired with either P or S considerably improved QTL detection power and accuracy, resulting in the identification of 105 QTLs and 617 QTL effects for 11 elements. Candidate gene search revealed some potential functional associations between QTLs and corresponding genes within their intervals. Thus, we have shown that accounting for variation in P and S is crucial for understanding of the physiological and genetic regulation of mineral composition of wheat grain ionome and can be implemented for other plants.
Mannerheim, N. ; Blessing, C. H. ; Oren, I. ; Grünzweig, J. ; Bachofen, C. ; Buchmann, N. Carbon allocation to the root system of tropical tree Ceiba pentandra using 13C pulse labelling in an aeroponic facility. Tree Physiol 2020, 40, 350 - 366. Publisher's VersionAbstract
Despite the important role of tropical forest ecosystems in the uptake and storage of atmospheric carbon dioxide (CO2), the carbon (C) dynamics of tropical tree species remains poorly understood, especially regarding belowground roots. This study assessed the allocation of newly assimilated C in the fast-growing pioneer tropical tree species Ceiba pentandra (L.), with a special focus on different root categories. During a 5-day pulse-labelling experiment, 9-month-old (~3.5-m-tall) saplings were labelled with 13CO2 in a large-scale aeroponic facility, which allowed tracing the label in bulk biomass and in non-structural carbohydrates (sugars and starch) as well as respiratory CO2 from the canopy to the root system, including both woody and non-woody roots. A combined logistic and exponential model was used to evaluate 13C mean transfer time and mean residence time (MRT) to the root systems. We found 13C in the root phloem as early as 2 h after the labelling, indicating a mean C transfer velocity of 2.4 ± 0.1 m h−1. Five days after pulse labelling, 27% of the tracers taken up by the trees were found in the leaves and 13% were recovered in the woody tissue of the trunk, 6% in the bark and 2% in the root systems, while 52% were lost, most likely by respiration and exudation. Larger amounts of 13C were found in root sugars than in starch, the former also demonstrating shorter MRT than starch. Of all investigated root categories, non-woody white roots (NRW) showed the largest 13C enrichment and peaked in the deepest NRW (2–3.5 m) as early as 24 ± 2 h after labelling. In contrast to coarse woody brown roots, the sink strength of NRW increased with root depth. The findings of this study improve the understanding of C allocation in young tropical trees and provide unique insights into the changing contributions of woody and non-woody roots to C sink strengths with depth.
Preisler, Y. ; Tatarinov, F. ; Grünzweig, J. ; Yakir, D. Seeking the “point of no return” in the sequence of events leading to mortality of mature trees. Plant, Cell & EnvironmentPlant, Cell & EnvironmentPlant Cell Environ 2020, n/a. Publisher's VersionAbstract
Abstract Drought-related tree mortality is increasing globally, but the sequence of events leading to it remains poorly understood. To identify this sequence, we used a 2016 tree mortality event in a semi-arid pine forest where dendrometry and sap flow measurements were carried out in 31 trees, of which seven died. A comparative analysis revealed three stages leading to mortality. First, a decrease in tree diameter in all dying trees, but not in the surviving trees, 8?months ?prior to the visual signs of mortality? (PVSM; e.g., near complete canopy browning). Second, a decay to near zero in the diurnal stem swelling/shrinkage dynamics, reflecting the loss of stem radial water flow in the dying trees, 6?months PVSM. Third, cessation of stem sap flow 3?months PVSM. Eventual mortality could therefore be detected long before visual signs were observed, and the three stages identified here demonstrated the differential effects of drought on stem growth, water storage capacity and soil water uptake. The results indicated that breakdown of stem radial water flow and phloem function is a critical element in defining the ?point of no return? in the sequence of events leading to mortality of mature trees.
Frankin, S. ; Kunta, S. ; Abbo, S. ; Sela, H. ; Goldberg, B. Z. ; Bonfil, D. J. ; Levy, A. A. ; Avivi-Ragolsky, N. ; Nashef, K. ; Roychowdhury, R. ; et al. The Israeli–Palestinian wheat landraces collection: restoration and characterization of lost genetic diversity. Journal of the Science of Food and AgricultureJournal of the Science of Food and AgricultureJ. Sci. Food Agric. 2020, 100, 4083 - 4092. Publisher's VersionAbstract
Abstract BACKGROUND For over a century, genetic diversity of wheat worldwide was eroded by continual selection for high yields and industrial demands. Wheat landraces cultivated in Israel and Palestine demonstrate high genetic diversity and a potentially wide repertoire of adaptive alleles. While most Israeli-Palestinian wheat landraces were lost in the transition to ?Green Revolution? semi-dwarf varieties, some germplasm collections made at the beginning of the 20th century survived in gene banks and private collections worldwide. However, fragmentation and poor conservation place this unique genetic resource at a high risk of genetic erosion. Herein, we describe a long-term initiative to restore, conserve, and characterize a collection of Israeli and Palestinian wheat landraces (IPLR). RESULTS We report on (i) the IPLR construction (n = 932), (ii) the historical and agronomic context to this collection, (iii) the characterization and assessment of the IPLR's genetic diversity, and (iv) a data comparison from two distinct subcollections within IPLR: a collection made by N. Vavilov in 1926 (IPLR-VIR) and a later one (1979?1981) made by Y. Mattatia (IPLR-M). Though conducted in the same eco-geographic space, these two collections were subjected to considerably different conservation pathways. IPLR-M, which underwent only one propagation cycle, demonstrated marked genetic and phenotypic variability (within and between accessions) in comparison with IPLR-VIR, which had been regularly regenerated over ?90?years. CONCLUSION We postulate that long-term ex?situ conservation involving human and genotype???environment selection may significantly reduce accession heterogeneity and allelic diversity. Results are further discussed in a broader context of pre-breeding and conservation. ? 2019 Society of Chemical Industry
Sade, D. ; Sade, N. ; Brotman, Y. ; Czosnek, H. Tomato yellow leaf curl virus (TYLCV)-resistant tomatoes share molecular mechanisms sustaining resistance with their wild progenitor Solanum habrochaites but not with TYLCV-susceptible tomatoes. Food Security under Climate Change 2020, 295, 110439. Publisher's VersionAbstract
The wild tomato species Solanum habrochaites (Sh) has been used as a source for tomato yellow leaf curl virus (TYLCV) resistance in a breeding program to generate a TYLCV-resistant tomato line. Susceptible (S) and resistant (R) lines have been developed through this program. We compared the behavior of R, S and Sh tomato plants upon infection to find out whether the resistant phenotype of R plants originated from Sh. Results showed that mechanisms involving sugar-signaling (i.e., LIN6/HT1), water channels (i.e., TIP1;1), hormone homeostasis (i.e., ABA and SA) and urea accumulation were shared by S. habrochaites and R plants, but not by S. habrochaites and S tomatoes. This finding supports the hypothesis that these mechanisms were introgressed in the R genotype from the wild tomato progenitor during breeding for TYLCV resistance. Hence, identification of genes contributing to resistance to biotic stress from wild tomato species and their introgression into domestic plants ensures tomato supply and food security.
Negin, B. ; Moshelion, M. Remember where you came from: ABA insensitivity is epigenetically inherited in mesophyll, but not seeds. Food Security under Climate Change 2020, 295, 110455. Publisher's VersionAbstract
Plants transmit their experiences of environmental conditions to their progeny through epigenetic inheritance, improving their progeny’s fitness under prevailing conditions. Though ABA is known to regulate epigenetic-modification genes, no strong phenotypic link between those genes and intergenerational “memory” has been shown. Previously, we demonstrated that mesophyll insensitivity to ABA (FBPase::abi1-1{fa} transgenic plants) results in a range of developmental phenotypes, including early growth vigor and early flowering (i.e., stress-escape behavior). Here, we show that null plants, used as controls (segregates of FBPase::abi1 that are homozygote descendants of a heterozygous transgenic plant, but do not contain the transformed abi1-1 gene) phenotypically resembled their FBPase::abi1-1 parents. However, in germination and early seedling development assays, null segregants resembled WT plants. These FBPase::abi1-1 null segregants mesophyll-related phenotypes were reproducible and stable for at least three generations. These results suggest that the heritability of stress response is linked to ABA’s epigenetic regulatory effect through ABI1 and mesophyll-related traits. The discrepancy between the epigenetic heritability of seed and mesophyll-related traits is an example of the complexity of epigenetic regulation, which is both gene and process-specific, and may be attributed to the fine-tuning of tradeoffs between flowering time, growth rate and levels of risk that allow annual plants to optimize their fitness in uncertain environments.
Gadri, Y. ; Eshed Williams, L. ; Peleg, Z. Tradeoffs between yield components promote crop stability in sesame. Food Security under Climate Change 2020, 295, 110105. Publisher's VersionAbstract
Sesame is an important oil-crop worldwide. Complex tradeoffs between various yield components significantly affect the outcome yield. Our aims were to characterize the effect of genotype, environment and management, and their interactions, on yield components. Wild-type line, bearing a bicarpellate-capsule and three capsules per leaf axil, and its derived mutant-line, featuring one tetracarpellate-capsule per leaf axil, were analyzed under two irrigation regimes and three sowing-stands. Dissection of flower meristems and capsules showed larger placenta size and final capsule diameter in the mutant-line. Allelic segregation of F2 population revealed that the number of carpels per capsule demonstrates monogenic inheritance, whereas the number of capsules per leaf axil is a polygenic trait. A significant effect of genotype, irrigation and stand was observed on most yield components. While wild-type had more capsules per plant, the mutant-line compensated by increased seed number per capsule and consequently accumulated the same number of seeds per plant. Under either high intra-row or inter-row density, the branches number was reduced; however, the outcome yield was compensated by number of plants per area. While some yield components showed phenotypic-plasticity (branching), other traits were genetically stable (number of capsules per leaf axil and number of carpels per capsule). Our result shed-light on tradeoffs between yield components and on their underlying mechanisms.
Steiner, E. ; Israeli, A. ; Gupta, R. ; Shwartz, I. ; Nir, I. ; Leibman-Markus, M. ; Tal, L. ; Farber, M. ; Amsalem, Z. ; Ori, N. ; et al. Characterization of the cytokinin sensor TCSv2 in arabidopsis and tomato. 2020, 16, 152. Publisher's VersionAbstract
Hormones are crucial to plant life and development. Being able to follow the plants hormonal response to various stimuli and throughout developmental processes is an important and increasingly widespread tool. The phytohormone cytokinin (CK) has crucial roles in the regulation of plant growth and development.
Gyan, N. M. ; Yaakov, B. ; Weinblum, N. ; Singh, A. ; Cna’ani, A. ; Ben-Zeev, S. ; Saranga, Y. ; Tzin, V. Variation Between Three Eragrostis tef Accessions in Defense Responses to Rhopalosiphum padi Aphid Infestation. 2020, 11, 1892. Publisher's VersionAbstract
Tef (Eragrostis tef), a staple crop that originated in the Horn of Africa, has been introduced to multiple countries over the last several decades. Crop cultivation in new geographic regions raises questions regarding the molecular basis for biotic stress responses. In this study, we aimed to classify the insect abundance on tef crop in Israel, and to elucidate its chemical and physical defense mechanisms in response to insect feeding. To discover the main pests of tef in the Mediterranean climate, we conducted an insect field survey on three selected accessions named RTC-144, RTC-405, and RTC-406, and discovered that the most abundant insect order is Hemiptera. We compared the differences in Rhopalosiphum padi (Hemiptera; Aphididae) aphid performance, preference, and feeding behavior between the three accessions. While the number of aphid progeny was lower on RTC-406 than on the other two, the aphid olfactory assay indicated that the aphids tended to be repelled from the RTC-144 accession. To highlight the variation in defense responses, we investigated the physical and chemical mechanisms. As a physical barrier, the density of non-granular trichomes was evaluated, in which a higher number of trichomes on the RTC-406 than on the other accessions was observed. This was negatively correlated with aphid performance. To determine chemical responses, the volatile and central metabolite profiles were measured upon aphid attack for 4 days. The volatile analysis exposed a rich and dynamic metabolic profile, and the central metabolism profile indicated that tef plants adjust their sugars and organic and amino acid levels. Overall, we found that the tef plants possess similar defense responses as other Poaceae family species, while the non-volatile deterrent compounds are yet to be characterized. A transcriptomic time-series analysis of a selected accession RTC-144 infested with aphids revealed a massive alteration of genes related to specialized metabolism that potentially synthesize non-volatile toxic compounds. This is the first report to reveal the variation in the defense mechanisms of tef plants. These findings can facilitate the discovery of insect-resistance genes leading to enhanced yield in tef and other cereal crops.
Yang, T. ; Feng, H. ; Zhang, S. ; Xiao, H. ; Hu, Q. ; Chen, G. ; Xuan, W. ; Moran, N. ; Murphy, A. ; Yu, L. ; et al. The Potassium Transporter OsHAK5 Alters Rice Architecture via ATP-Dependent Transmembrane Auxin Fluxes. 2020, 1 100052. Publisher's VersionAbstract
Plant HAK/KUP/KT family members function as plasma membrane (PM) H+/K+ symporters and may modulate chemiosmotically-driven polar auxin transport (PAT). Here, we show that inactivation of OsHAK5, a rice K+ transporter gene, decreased rootward and shootward PAT, tiller number, and the length of both lateral roots and root hairs, while OsHAK5 overexpression increased PAT, tiller number, and root hair length, irrespective of the K+ supply. Inhibitors of ATP-binding-cassette type-B transporters, NPA and BUM, abolished the OsHAK5-overexpression effect on PAT. The mechanistic basis of these changes included the OsHAK5-mediated decrease of transmembrane potential (depolarization), increase of extracellular pH, and increase of PM-ATPase activity. These findings highlight the dual roles of OsHAK5 in altering cellular chemiosmotic gradients (generated continuously by PM H+-ATPase) and regulating ATP-dependent auxin transport. Both functions may underlie the prominent effect of OsHAK5 on rice architecture, which may be exploited in the future to increase crop yield via genetic manipulations.
Karniel, U. ; Koch, A. ; Zamir, D. ; Hirschberg, J. Development of zeaxanthin-rich tomato fruit through genetic manipulations of carotenoid biosynthesis. Plant Biotechnology Journal 2020, 18, 2292-2303. Publisher's VersionAbstract
Summary The oxygenated carotenoid zeaxanthin provides numerous benefits to human health due to its antioxidant properties. Especially it is linked to protecting, together with the xanthophyll lutein, the retina in the human eye by filtering harmful blue light thus delaying the progression of age-related macular degeneration (AMD), the most prevalent cause of blindness in developed countries. Despite its high nutritional value, zeaxanthin is less available than other substantial carotenoids in our diet. To solve this shortage, we chose to develop a new food source that would contain a high concentration of natural zeaxanthin. Tomato (Solanum lycopersicum L.) was selected as the target plant since it is the second largest vegetable crop grown worldwide and its fruit characteristically synthesizes and accumulates a high concentration of carotenoids. We employed two genetic approaches in order to enhance zeaxanthin biosynthesis in tomato fruit: a transgenic metabolic engineering and classical genetic breeding. A nontransgenic tomato line, named ‘Xantomato’, was generated whose fruit accumulated zeaxanthin at a concentration of 39 μg/g fresh weight (or 577 μg/g dry weight), which comprised ca. 50% of total fruit carotenoids compared to zero in the wild type. This is the highest concentration of zeaxanthin reached in a primary crop. Xantomato can potentially increase zeaxanthin availability in the human diet and serve as raw material for industrial applications.
Szymański, J. ; Bocobza, S. ; Panda, S. ; Sonawane, P. ; Cárdenas, P. D. ; Lashbrooke, J. ; Kamble, A. ; Shahaf, N. ; Meir, S. ; Bovy, A. ; et al. Analysis of wild tomato introgression lines elucidates the genetic basis of transcriptome and metabolome variation underlying fruit traits and pathogen response. 2020, 52, 1111 - 1121. Publisher's VersionAbstract
Wild tomato species represent a rich gene pool for numerous desirable traits lost during domestication. Here, we exploited an introgression population representing wild desert-adapted species and a domesticated cultivar to establish the genetic basis of gene expression and chemical variation accompanying the transfer of wild-species-associated fruit traits. Transcriptome and metabolome analysis of 580 lines coupled to pathogen sensitivity assays resulted in the identification of genomic loci associated with levels of hundreds of transcripts and metabolites. These associations occurred in hotspots representing coordinated perturbation of metabolic pathways and ripening-related processes. Here, we identify components of the Solanum alkaloid pathway, as well as genes and metabolites involved in pathogen defense and linking fungal resistance with changes in the fruit ripening regulatory network. Our results outline a framework for understanding metabolism and pathogen resistance during tomato fruit ripening and provide insights into key fruit quality traits.
Kliot, A. ; Johnson, R. S. ; MacCoss, M. J. ; Kontsedalov, S. ; Lebedev, G. ; Czosnek, H. ; Heck, M. ; Ghanim, M. A proteomic approach reveals possible molecular mechanisms and roles for endosymbiotic bacteria in begomovirus transmission by whiteflies. Gigascience 2020, 9. Publisher's VersionAbstract
Many plant viruses are vector-borne and depend on arthropods for transmission between host plants. Begomoviruses, the largest, most damaging and emerging group of plant viruses, infect hundreds of plant species, and new virus species of the group are discovered each year. Begomoviruses are transmitted by members of the whitefly Bemisia tabaci species complex in a persistent-circulative manner. Tomato yellow leaf curl virus (TYLCV) is one of the most devastating begomoviruses worldwide and causes major losses in tomato crops, as well as in many agriculturally important plant species. Different B. tabaci populations vary in their virus transmission abilities; however, the causes for these variations are attributed among others to genetic differences among vector populations, as well as to differences in the bacterial symbionts housed within B. tabaci.Here, we performed discovery proteomic analyses in 9 whitefly populations from both Middle East Asia Minor I (MEAM1, formerly known as B biotype) and Mediterranean (MED, formerly known as Q biotype) species. We analysed our proteomic results on the basis of the different TYLCV transmission abilities of the various populations included in the study. The results provide the first comprehensive list of candidate insect and bacterial symbiont (mainly Rickettsia) proteins associated with virus transmission.Our data demonstrate that the proteomic signatures of better vector populations differ considerably when compared with less efficient vector populations in the 2 whitefly species tested in this study. While MEAM1 efficient vector populations have a more lenient immune system, the Q efficient vector populations have higher abundance of proteins possibly implicated in virus passage through cells. Both species show a strong link of the facultative symbiont Rickettsia to virus transmission.
Kumar, S. ; Natalio, F. ; Elbaum, R. Protein-driven biomineralization: comparing silica formation in grass silica cells to other biomineralization processes. Journal of Structural Biology 2020, 107665. Publisher's VersionAbstract
Biomineralization is a common strategy adopted by organisms to support their body structure. Plants practice significant silicon and calcium based biomineralization in which silicon is deposited as silica in cell walls and intracellularly in various cell-types, while calcium is deposited mostly as calcium oxalate in vacuoles of specialized cells. In this review, we compare cellular processes leading to protein-dependent mineralization in plants, diatoms and sponges (phylum Porifera). The mechanisms of biomineralization in these organisms are inherently different. The composite silica structure in diatoms forms inside the cytoplasm in a membrane bound vesicle, which after maturation is exocytosed to the cell surface. In sponges, separate vesicles with the mineral precursor (silicic acid), an inorganic template, and organic molecules, fuse together and are extruded out. In plants, calcium oxalate precursors are concentrated in a vacuolar vesicle containing a protein matrix which is never exocytosed. Silica deposition in grass silica cells takes place outside the cell membrane when the cells secrete the mineralizing protein into the apoplasm rich with silicic acid (the mineral precursor molecules). Our review infers that the organism complexity and precursor reactivity (calcium and oxalate versus silicic acid) are main driving forces for the evolution of varied mineralization mechanisms.