Plant Domestication in the Near East
. In Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures
; Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures; Springer Netherlands: Dordrecht, 2014; pp. 1–9. Publisher's Version
The 'Human Mind' as a common denominator in plant domestication
. Journal of Experimental Botany 2014
, 1917-1920. Publisher's VersionAbstract
The role of conscious versus unconscious selection is a central issue in plant domestication. While some authors hold that domesticated plants arose due to unconscious dynamics driven by selection pressures exerted by the ancient 'cultivation regime', others attribute an indispensable role to conscious and knowledge-based selection as an imperative component of Neolithic Near Eastern plant domestication. Recent experimental work demonstrated that, contrary to commonly held views, deep seed burial as part of the ancient cultivation regime cannot be considered as a general selection pressure underlying the increased seed size of domesticated legumes compared with their wild ancestors. This is a robust conclusion since, in three out of the eight legume species studied from different world regions, there was no association between larger seed size and better seedling emergence from depth. We concur with the authors that these legume crops were most likely under various and multiple (often interacting) selection pressures under domestication, thereby causing the observed parallel/convergent evolution of their larger grain size. However, it is puzzling that these authors did not mention the ever-present common denominator in plant domestication, i.e. conscious human decision-making. In our view, the human 'Mind' and the 'Science of the Concrete' à la Lévi-Strauss deserved to be discussed as an integral component of plant domestication. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.
Novel quantitative trait loci underlying major domestication traits in tetraploid wheat
. Molecular Breeding 2014
, 1613-1628. Publisher's VersionAbstract
Wheat domestication and subsequent evolution under domestication occurred since the dawn of agriculture and caused significant genetic changes that affected plant morphology, physiology and phenology. The majority of these traits are quantitative traits controlled by many genes. Correspondingly, the main goal of the current study is genetic dissection of the key domestication trait (brittle rachis) and traits evolved under domestication, based on quantitative phenotyping. Genetic mapping of quantitative trait loci (QTL) affecting brittle rachis, threshability, threshing efficiency, spike harvest index and kernel weight was conducted using a recombinant inbred lines population derived from a cross between Triticum durum and wild emmer wheat. Using a new quantitative phenotyping approach, we discovered novel QTLs underlying rachis fragility, spike threshability and other domestication-related traits and confirmed some of the known putative locations for QTLs affecting these traits. Overall, the number of domestication-related QTLs mapped to the A genome was twofold higher than those found on the B genome, in accordance with the concept of ‘genome asymmetry’, implying that the A genome is dedicated to the control of morphological traits, house-keeping metabolic reactions and yield components. Our results add a new dimension to this important concept and contribute to a better understanding of the initial steps of domestication evolution of cereals. © 2014, Springer Science+Business Media Dordrecht.
Plant domestication versus crop evolution: A conceptual framework for cereals and grain legumes
. Trends in Plant Science 2014
, 351-360. Publisher's VersionAbstract
'Domestication syndrome' (DS) denotes differences between domesticated plants and their wild progenitors. Crop plants are dynamic entities; hence, not all parameters distinguishing wild progenitors from cultigens resulted from domestication. In this opinion article, we refine the DS concept using agronomic, genetic, and archaeobotanical considerations by distinguishing crucial domestication traits from traits that probably evolved post-domestication in Near Eastern grain crops. We propose that only traits showing a clear domesticated-wild dimorphism represent the pristine domestication episode, whereas traits showing a phenotypic continuum between wild and domesticated gene pools mostly reflect post-domestication diversification. We propose that our approach may apply to other crop types and examine its implications for discussing the timeframe of plant domestication and for modern plant science and breeding. © 2013 Elsevier Ltd.
The potential use of chickpeas in development of infant follow-on formula
. Nutrition Journal 2014
. Publisher's VersionAbstract
Background: Undernutrition during childhood is a common disorder in the developing countries, however most research has focussed much on its treatment rather than its prevention. Objective. We investigated the potential of using chickpeas in infant follow-on formula production against the requirements of WHO/FAO on complementary foods and EU regulations on follow-on formula. Methods. Chickpeas were germinated for 72 hours followed by boiling, drying and dehulling in order to minimise associated anti-nutrition factors. Saccharifying enzymes were used to hydrolyse starch to maltose and the resulting flours were analysed for their protein content and amino acid profile. Results: The protein content (percentage) increased from 16.66 ± 0.35 and 20.24 ± 0.50 to 20.00 ± 0.15 and 21.98 ± 0.80 for the processed desi and kabuli cultivar compared to raw chickpeas, respectively (P < 0.05). There was insignificant change (P = 0.05) in amino acid profile following processing and the resulting flour was found to meet the amino acid requirements of WHO/FAO protein reference for 0-24 month's children. Conclusion: The designed chickpea based infant follow-on formula meets the WHO/FAO requirements on complementary foods and also the EU regulations on follow-on formula with minimal addition of oils, minerals and vitamins. It uses chickpea as a common source of carbohydrate and protein hence making it more economical and affordable for the developing countries without compromising the nutrition quality. © 2014 Malunga et al.; licensee BioMed Central Ltd.
The genome of the stress-tolerant wild tomato species Solanum pennellii
. Nature Genetics 2014
, 1034-1038. Publisher's VersionAbstract
Solanum pennellii is a wild tomato species endemic to Andean regions in South America, where it has evolved to thrive in arid habitats. Because of its extreme stress tolerance and unusual morphology, it is an important donor of germplasm for the cultivated tomato Solanum lycopersicum. Introgression lines (ILs) in which large genomic regions of S. lycopersicum are replaced with the corresponding segments from S. pennellii can show remarkably superior agronomic performance. Here we describe a high-quality genome assembly of the parents of the IL population. By anchoring the S. pennellii genome to the genetic map, we define candidate genes for stress tolerance and provide evidence that transposable elements had a role in the evolution of these traits. Our work paves a path toward further tomato improvement and for deciphering the mechanisms underlying the myriad other agronomic traits that can be improved with S. pennellii germplasm. © 2014 Nature America, Inc. All rights reserved.
Genomic analyses provide insights into the history of tomato breeding
; Nature Genetics; 2014; Vol. 46, pp. 1220-1226. Publisher's VersionAbstract
The histories of crop domestication and breeding are recorded in genomes. Although tomato is a model species for plant biology and breeding, the nature of human selection that altered its genome remains largely unknown. Here we report a comprehensive analysis of tomato evolution based on the genome sequences of 360 accessions. We provide evidence that domestication and improvement focused on two independent sets of quantitative trait loci (QTLs), resulting in modern tomato fruit a 1/4100 times larger than its ancestor. Furthermore, we discovered a major genomic signature for modern processing tomatoes, identified the causative variants that confer pink fruit color and precisely visualized the linkage drag associated with wild introgressions. This study outlines the accomplishments as well as the costs of historical selection and provides molecular insights toward further improvement. © 2014 Nature America, Inc. All rights reserved.
Optimization of crop productivity in tomato using induced mutations in the florigen pathway
. Nature Genetics 2014
, 1337-1342. Publisher's VersionAbstract
Naturally occurring genetic variation in the universal florigen flowering pathway has produced major advancements in crop domestication. However, variants that can maximize crop yields may not exist in natural populations. Here we show that tomato productivity can be fine-tuned and optimized by exploiting combinations of selected mutations in multiple florigen pathway components. By screening for chemically induced mutations that suppress the bushy, determinate growth habit of field tomatoes, we isolated a new weak allele of the florigen gene SINGLE FLOWER TRUSS (SFT) and two mutations affecting a bZIP transcription factor component of the 'florigen activation complex' (ref. 11). By combining heterozygous mutations, we pinpointed an optimal balance of flowering signals, resulting in a new partially determinate architecture that translated to maximum yields. We propose that harnessing mutations in the florigen pathway to customize plant architecture and flower production offers a broad toolkit to boost crop productivity. © 2014 Nature America, Inc. All rights reserved.
The tomato mutation nxd1 reveals a gene necessary for neoxanthin biosynthesis and demonstrates that violaxanthin is a sufficient precursor for abscisic acid biosynthesis
. Plant Journal 2014
, 80-93. Publisher's VersionAbstract
Carotenoid pigments are indispensable for plant life. They are synthesized within plastids where they provide essential functions in photosynthesis. Carotenoids serve as precursors for the synthesis of the strigolactone phytohormones, which are made from β-carotene, and of abscisic acid (ABA), which is produced from certain xanthophylls. Despite the significant progress that has been made in our understanding of the carotenoid biosynthesis pathway, the synthesis of the xanthophyll neoxanthin has remained unknown. We report here on the isolation of a tomato (Solanum lycopersicum) mutant, neoxanthin-deficient 1 (nxd1), which lacks neoxanthin, and on the cloning of a gene that is necessary for neoxanthin synthesis in both tomato and Arabidopsis. The locus nxd1 encodes a gene of unknown function that is conserved in all higher plants. The activity of NXD1 is essential but cannot solely support neoxanthin synthesis. Lack of neoxanthin does not significantly reduce the fitness of tomato plants in cultivated field conditions and does not impair the synthesis of ABA, suggesting that in tomato violaxanthin is a sufficient precursor for ABA production in vivo. © 2014 John Wiley & Sons Ltd.
Iron uptake mechanism in the chrysophyte microalga Dinobryon
. Journal of Plant Physiology 2014
, 993-997. Publisher's VersionAbstract
The mechanism of iron uptake in the chrysophyte microalga Dinobryon was studied. Previous studies have shown that iron is the dominant limiting elements for growth of Dinobryon in the Eshkol reservoir in northern Israel, which control its burst of bloom. It is demonstrated that Dinobryon has a light-stimulated ferrireductase activity, which is sensitive to the photosynthetic electron transport inhibitor DCMU and to the uncoupler CCCP. Iron uptake is also light-dependent, is inhibited by DCMU and by CCCP and also by the ferrous iron chelator BPDS. These results suggest that ferric iron reduction by ferrireductase is involved in iron uptake in Dinobryon and that photosynthesis provides the major reducing power to energize iron acquisition. Iron deprivation does not enhance but rather inhibits iron uptake contrary to observations in other algae. © 2014 Elsevier GmbH.
The effect of screenhouse height on air temperature
. Acta Horticulturae 2014
, 517-524. Publisher's VersionAbstract
The use of screenhouses in protected cultivation is nowadays a common practice in many countries. When fine mesh screens are used in the screenhouse construction, the resistance of the screens to airflow is high and ventilation rate is strongly reduced in comparison to the open field. Thus, growers tend to move to higher screenhouses since they assume that in such structures accumulation of warm and humid air near the plants is diminished. The goal of this research was to investigate, in insect-proof screenhouses, the effect of screenhouse height on air temperature. Experiments were conducted in two flat top screenhouses each of an area of 745 m2; one with a roof height of 4 m (LSH) and the other with a roof height of 6 m (HSH) with 16 m of separation between them. The houses were covered with a '50-mesh' screen which is commonly used with tomato cultivation in Israel. The daily courses of air temperature were very similar in the two houses. The average air temperature in the HSH was nearly at all times higher than in the LSH. The largest differences in temperature between the houses, of about 1°C, were observed during day; slightly lower differences were observed during night. The most significant difference between the two houses was related to the vertical gradients of temperature. The results show that the microclimate in the vertical direction appears to be more homogenous in the HSH than in the LSH.
Effects of high salinity irrigation on growth, gas-exchange, and photoprotection in date palms (Phoenix dactylifera L., cv. Medjool)
. Environmental and Experimental Botany 2014
, 100-109. Publisher's VersionAbstract
Date palms are widely cultivated in arid Mediterranean regions and require large quantities of water to produce commercial fruit yields. In these regions the plantations are commonly irrigated with low-quality water, which results in reduced growth and yields. To study the effect of using saline water for irrigation, date palm seedlings (cv. Medjool) were subjected to long-term irrigation treatments with water containing between 2 and 105mM NaCl. The effect of saline irrigation was determined according to leaf gas exchange, chlorophyll a fluorescence, growth parameters and the distribution of key minerals in different plant organs. High salinity decreased plant growth and increased Na+ accumulation in the roots and lower stem. However, Na+ ions were mostly excluded from the sensitive photosynthetic tissues of the leaf. Thus, the reduction in the CO2 assimilation rate was primarily attributed to a reduced stomatal conductance. Consistent with this finding, the photosynthetic response to variable intercellular CO2 concentrations (A/Ci curves) revealed no permanent damage to the photosynthetic apparatus and implicated developed photoprotective mechanisms. Independent of salinity treatment, 80% of the energy absorbed by the leaf was directed to non-photochemical quenching, as presented in electron-equivalent units. Functioning at full capacity, the non-photochemical mechanism could not compensate for all the excess irradiance. Thus, of the remaining absorbed energy, a significant portion was directed to photochemical O2 related processes, rather than CO2 prevented photoinhibition. The exclusion of toxic ions and O2-dependent energy dissipation maintained photosynthetic efficiency and supported survival under salt stress. © 2013 Elsevier B.V.
A model for computing date palm water requirements as affected by salinity
. Irrigation Science 2014
, 341-350. Publisher's VersionAbstract
Irrigation of crops in arid regions with marginal water is expanding. Due to economic and environmental issues arising from use of low-quality water, irrigation should follow the actual crop water demands. However, direct measurements of transpiration are scant, and indirect methods are commonly applied; e.g., the Penman-Monteith (PM) equation that integrates physiological and meteorological parameters. In this study, the effects of environmental conditions on canopy resistance and water loss were experimentally characterized, and a model to calculate palm tree evapotranspiration ETc was developed. A novel addition was to integrate water salinity into the model, thus accounting for irrigation water quality as an additional factor. Palm tree ETc was affected by irrigation water salinity, and maximum values were reduced by 25 % in plants irrigated with 4 dS m-1 and by 50 % in the trees irrigated with 8 dS m-1. Results relating the responses of stomata to the environment exhibited an exponential relation between increased light intensities and stomatal conductance, a surprising positive response of stomata to high vapor pressure deficits and a decrease in conductance as water salinity increased. These findings were integrated into a modified 'Jarvis-PM' canopy conductance model using only meteorological and water quality inputs. The new approach produced weekly irrigation recommendations based on field water salinity (2.8 dS m-1) and climatic forecasts that led to a 20 % decrease in irrigation water use when compared with current irrigation recommendations. © 2014 Springer-Verlag Berlin Heidelberg.
Sodium replacement of potassium in physiological processes of olive trees (var. Barnea) as affected by drought
. Tree Physiology 2014
, 1102-1117. Publisher's VersionAbstract
Potassium (K) is a macro-nutrient understood to play a role in the physiological performance of plants under drought. In some plant species, sodium (Na) can partially substitute K. Although a beneficial role of Na is well established, information regarding its nutritional role in trees is scant and its function under conditions of drought is not fully understood. The objective of the present study was to evaluate the role of K and its possible replacement by Na in olive's (Olea europaea L.) response to drought. Young and bearing olive trees were grown in soilless culture and exposed to gradual drought. In the presence of Na, trees were tolerant of extremely low K concentrations. Depletion of K and Na resulted in ∼50% reduction in CO2 assimilation rate when compared with sufficiently fertilized control plants. Sodium was able to replace K and recover the assimilation rate to nearly optimum level. The inhibitory effect of K deficiency on photosynthesis was more pronounced under high stomatal conductance. Potassium was not found to facilitate drought tolerance mechanisms in olives. Moreover, stomatal control machinery was not significantly impaired by K deficiency, regardless of water availability. Under drought, leaf water potential was affected by K and Na. High environmental K and Na increased leaf starch content and affected the soluble carbohydrate profile in a similar manner. These results identify olive as a species capable of partly replacing K by Na. The nutritional effect of K and Na was shown to be independent of plant water status. The beneficial effect of Na on photosynthesis and carbohydrates under insufficient K indicates a positive role of Na in metabolism and photosynthetic reactions. © The Author 2014. Published by Oxford University Press. All rights reserved.
Effects of irrigation using treated wastewater on table grape vineyards: Dynamics of sodium accumulation in soil and plant
. Irrigation Science 2014
, 283-294. Publisher's VersionAbstract
The effect of using treated wastewater for irrigation of table grapes (Vitis vinifera cv. Superior Seedless) was studied for six seasons. The experimental vineyard was grown on clay loam soil in a semi-arid area. Treated wastewater (5.83 meq L-1 Na+) with (TWW + F) and without (TWW) fertilizer, and fresh water with fertilizer (FW + F, 2.97 meq L-1 Na+), were each applied at three irrigation levels (80, 60 and 40 % of crop evapotranspiration before harvest). Root zone (0-60 cm soil depth) soil saturated paste extract Na+ concentrations and sodium adsorption ratio (SAR) values fluctuated over the years, but generally decreased in the order TWW > TWW + F > FW + F for each irrigation level. Both Na+ concentrations and SAR values developed faster and to a greater extent at higher irrigation. Adding fertilizer to TWW decreased Na+ and SAR only at the high irrigation level. Na+ concentrations in the trunk wood, bark and xylem sap of the TWW and TWW + F irrigated vines were significantly higher than those in the FW + F-irrigated vines. Leaf petiole Na+ content increased with time and its maximum value in TWW and TWW + F irrigated vines exceeded 6,500 mg kg-1, threefold higher than in FW + F irrigated vines. We conclude that in clay soils under relatively high irrigation, Na+ may pose a greater potential risk to plants and soil rather than Cl- or salinity per se. However, significant effects on yield were not recorded during this six-year study probably due to the high salinity tolerance of the 'Paulsen' rootstock used in the experiment. © 2014 Springer-Verlag Berlin Heidelberg.
Do phosphoinositides regulate membrane water permeability of tobacco protoplasts by enhancing the aquaporin pathway?
. Planta 2014
, 741-755. Publisher's VersionAbstract
Main conclusion: Enhancing the membrane content of PtdInsP2, the already-recognized protein-regulating lipid, increased the osmotic water permeability of tobacco protoplasts, apparently by increasing the abundance of active aquaporins in their membranes. While phosphoinositides are implicated in cell volume changes and are known to regulate some ion channels, their modulation of aquaporins activity has not yet been reported for any organism. To examine this, we compared the osmotic water permeability (Pf) of protoplasts isolated from tobacco (Nicotiana tabacum) cultured cells (NT1) with different (genetically lowered or elevated relative to controls) levels of inositol trisphosphate (InsP3) and phosphatidyl inositol [4,5] bisphosphate (PtdInsP2). To achieve this, the cells were transformed with, respectively, the human InsP3 5-phosphatase (‘Ptase cells’) or human phosphatidylinositol (4) phosphate 5-kinase (‘PIPK cells’). The mean Pf of the PIPK cells was several-fold higher relative to that of controls and Ptase cells. Three results favor aquaporins over the membrane matrix as underlying this excessive Pf: (1) transient expression of the maize aquaporin ZmPIP2;4 in the PIPK cells increased Pf by 12–30 μm s−1, while in the controls only by 3–4 μm s−1. (2) Cytosol acidification—known to inhibit aquaporins—lowered the Pf in the PIPK cells down to control levels. (3) The transcript of at least one aquaporin was elevated in the PIPK cells. Together, the three results demonstrate the differences between the PIPK cells and their controls, and suggest a hitherto unobserved regulation of aquaporins by phosphoinositides, which could occur through direct interaction or indirect phosphoinositides-dependent cellular effects. © 2014, Springer-Verlag Berlin Heidelberg.
Is the leaf bundle sheath a "smart flux valve" for K+ nutrition?
. Journal of Plant Physiology 2014
, 715-722. Publisher's VersionAbstract
Evidence has started to accumulate that the bundle sheath regulates the passage of water, minerals and metabolites between the mesophyll and the conducting vessels of xylem and phloem within the leaf veins which it envelops. Although potassium (K+) nutrition has been studied for several decades, and much is known about the uptake and recirculation of K+ within the plant, the potential regulatory role of bundle sheath with regard to K+ fluxes has just begun to be addressed. Here we have collected some facts and ideas about these processes. © 2014 Elsevier GmbH.
Measuring the osmotic water permeability coefficient (pf) of spherical cells: Isolated plant protoplasts as an example
. Journal of Visualized Experiments 2014
. Publisher's VersionAbstract
Studying AQP regulation mechanisms is crucial for the understanding of water relations at both the cellular and the whole plant levels. Presented here is a simple and very efficient method for the determination of the osmotic water permeability coefficient (Pf) in plant protoplasts, applicable in principle also to other spherical cells such as frog oocytes The first step of the assay is the isolation of protoplasts from the plant tissue of interest by enzymatic digestion into a chamber with an appropriate isotonic solution The second step consists of an osmotic challenge assay: protoplasts immobilized on the bottom of the chamber are submitted to a constant perfusion starting with an isotonic solution and followed by a hypotonic solution. The cell swelling is video recorded. In the third step, the images are processed offline to yield volume changes, and the time course of the volume changes is correlated with the time course of the change in osmolarity of the chamber perfusion medium, using a curve fitting procedure written in Matlab (the ‘PfFit’), to yield Pf. © JoVE 2006-2014. All Rights Reserved.
The role of a potassium transporter oshak5 in potassium acquisition and transport from roots to shoots in rice at low potassium supply levels
. Plant Physiology 2014
, 945-959. Publisher's VersionAbstract
In plants, K transporter (KT)/high affinity K transporter (HAK)/K uptake permease (KUP) is the largest potassium (K) transporter family; however, few of the members have had their physiological functions characterized in planta. Here, we studied OsHAK5 of the KT/HAK/KUP family in rice (Oryza sativa). We determined its cellular and tissue localization and analyzed its functions in rice using both OsHAK5 knockout mutants and overexpression lines in three genetic backgrounds. A b-glucuronidase reporter driven by the OsHAK5 native promoter indicated OsHAK5 expression in various tissue organs from root to seed, abundantly in root epidermis and stele, the vascular tissues, and mesophyll cells. Net K influx rate in roots and K transport from roots to aerial parts were severely impaired by OsHAK5 knockout but increased by OsHAK5 overexpression in 0.1 and 0.3 mM K external solution. The contribution of OsHAK5 to K mobilization within the rice plant was confirmed further by the change of K concentration in the xylem sap and K distribution in the transgenic lines when K was removed completely from the external solution. Overexpression of OsHAK5 increased the K-sodium concentration ratio in the shoots and salt stress tolerance (shoot growth), while knockout of OsHAK5 decreased the K-sodium concentration ratio in the shoots, resulting in sensitivity to salt stress. Taken together, these results demonstrate that OsHAK5 plays a major role in K acquisition by roots faced with low external K and in K upward transport from roots to shoots in K-deficient rice plants. © 2014 American Society of Plant Biologists. All Rights Reserved.