The Search for Wild Relatives of Cool Season Legumes
; Springer International Publishing, 2015; pp. 103. Publisher's VersionAbstract
Brings together research findings that have been accumulated during the last 40 years, mainly by the authors, on wild relatives of cool season legumes
Indicates the wild relatives of lentil, chickpea, common and bitter vetch that can be exploited for breeding
Presents biological evidence that pulse domestication proceeded in a unique course, already in the wild
The study of origin and domestication of legumes described in this book emerged when it became apparent that while this kind of information is adequate for cereals, the pulses lagged behind. At the end of the 1960s the senior author initiated a study on the chickpea's wild relatives followed by similar attempts for broad bean, fenugreek, common vetch, bitter vetch, and lentil. The junior author joined the project in the late 1980s with a study of the genetics of interspecific hybrid embryo abortion in lentil and later has extensively investigated chickpea domestication and wild peas. While this book mainly describes our research findings, pertinent results obtained by others are also discussed and evaluated. Studying the wild relatives of legumes included evaluation of their taxonomic status, their morphological variation, ecological requirements, exploration of their distribution, and seed collection in their natural habitats. Seeds were examined for their protein profile as preliminary hints of their affinity to the cultigens and plants grown from these seeds were used for establishing their karyotype, producing intra- and interspecific hybrids and analyses of their chromosome pairing at meiosis and fertility. The aim of these investigations was the identification of the potential wild gene pool of the domesticated forms. Assessment of genetic variation among accessions, particularly in the genus Lens, was made by isozymes and chloroplast DNA studies. The main findings include the discovery of the chickpea wild progenitor; studies of lentil in three crossability groups; wild peas proceeded in two lines of study; faba bean and fenugreek and their wild progenitors have not yet been identified; common vetch and its related form were treated here as an aggregate (A. sativa); we found gene flow between members of different karyotypes is possible; bitter vetch and its relation to the domesticated form were established by breeding experiments.
Allelic diversity between and within three wild annual Cicer species
. Genetic Resources and Crop Evolution 2015
, 177-188. Publisher's VersionAbstract
Most wild Cicer species have narrow eco-geographic amplitude. Likewise, domesticated chickpea suffers from severe adaptive limitations due to its unique evolutionary history. The wild progenitor may offer only limited adaptive allelic variation for improving the chickpea crop. Therefore, there is a need to explore allelic diversity between and within annual Cicer sp. that span diverse natural habitats. Here we characterized the allelic diversity between and within wild populations of C. pinnatifidum, C. judaicum and C. cuneatum spanning most of their documented native range in Turkey, Israel and Ethiopia. Eco-geographical analysis resulted in clear separation between the collection sites of C. cuneatum in east Africa and the other two east Mediterranean species. Analysis of molecular variance shows that only 18 % of the allelic variation accounts for differences between the three species, while 34 % was contributed from difference between populations. Interestingly, most (48 %) of the allelic variation was detected among accessions within populations. PCoA analysis confirmed the independent taxonomic and indeed the genetic integrity of the two east Mediterranean sister species C. pinnatifidum and C. judaicum. Conservation of large rich populations seems a more effective strategy than the preservation of small thin populations of annual Cicer sp. Given the relatively narrow geographic range of most annual Cicer sp., accessing germplasm lines from ecologically distinct habitats emerges as the most promising strategy for the identification of useful adaptive allelic variation. © 2014, Springer Science+Business Media Dordrecht.
Fruit Domestication in the Near East
. Plant Breeding Reviews 2015
, 325-378. Publisher's VersionAbstract
Following the emergence of farming societies in the Neolithic Near East, a number of fruit trees were domesticated and became an integral part of the mixed farming economy of the region. These include emblematic crops such as olive, grape vine, date palm, fig, and pomegranate, as well as almond and carob. Unlike the Near Eastern founder grain crops that are thought to have originated in a relatively small “core area” and spread from there as a harmonic agro-economic package, Near Eastern fruit trees were adopted from several geographically remote and ecologically distinct areas: olive and carob in the east Mediterranean, grape vine and fig in the trans-Caucasus, pomegranate and almond in central Asia, and date palm in lower Mesopotamia. Following domestication, and owing to their reproductive biology (open pollination), extensive (bidirectional) domesticated–wild gene flow is thought to have had a major role in the emergence of new cultivars and in shaping the adaptation pattern of these species both under domestication and in nature. The reproductive biology and growth pattern of these fruit trees suggest that conscious (rather than unconscious) selection played a major role in the adoption of these taxa from the wild, in the development of special agro-techniques required to ensure sustainable production, and in developing methods for processing and long-term preservation of the fruit yield. Some authors see a phenotypic continuum between a wild erratic fruit yield pattern (often masting), alternate bearing, and a regular fruiting pattern typical of some domesticated trees, but we consider masting behavior and alternate bearing as two distinct developmental phenomena, probably controlled by different genetic systems that do not represent a genuine evolutionary continuum. The adoption of fruit trees necessitated and was mediated by a number of sociocultural adaptations that include a higher level of delayed return, long-term land allocation, and resource and labor investment in processing and storage facilities. As such, fruit tree domestication could have occurred only after the domestication of annual grain crops and the establishment of farming-based communities across West Asia. Copyright © 2015 by Wiley-Blackwell. All rights reserved
Sowing date and wheat quality as determined by gluten index
. Crop Science 2015
, 2294-2306. Publisher's VersionAbstract
Wheat (Triticum aestivum L.) in Mediterranean regions is highly variable in end-use quality at the producer level. This study aimed to understand how sowing date affects wheat quality, especially gluten index (GI). Experiments were conducted in five fields over three consecutive seasons in 2009–2011. Twenty cultivars (four of which were common to all experiments) were sown from late October to mid-January on three dates (early, normal, and late) in each field. Grain yield, test weight, protein content,GI, sodium dodecyl sulfate (SDS) sedimentation, and alveograph parameters were analyzed. The GI of the four common cultivars showed a significant environment (experiment) × cultivar × sowing date interaction. In two experiments, GI increased with a delay in sowing; in two other experiments, a similar increase resulted from delaying sowing from the early to normal sowing dates but there was no further increase following late sowing or in one experiment where GI was unaffected by sowing date. Hence, delayed sowing mostly increased GI, except where weed or severe drought stress prevailed. Similarly, dough tenacity increased with delayed sowing. A high correlation was found among grain protein, wet gluten contents, SDS sedimentation, and alveograph index. Wheat GI was not a good predictor of quality and did not correlate with other parameters, whereas flour GI showed better correlations. Hence, we suggest delaying sowing (from late October to mid-January) to increase GI and that GI should be used with caution as a quality predictor. Instead of GI, using different methods may improve the determination of wheat quality. © Crop Science Society of America. All rights reserved.
Transcriptome profiling of wheat glumes in wild emmer, hulled landraces and modern cultivars
. BMC Genomics 2015
. Publisher's VersionAbstract
Background: Wheat domestication is considered as one of the most important events in the development of human civilization. Wheat spikelets have undergone significant changes during evolution under domestication, resulting in soft glumes and larger kernels that are released easily upon threshing. Our main goal was to explore changes in transcriptome expression in glumes that accompanied wheat evolution under domestication. Methods: A total of six tetraploid wheat accessions were selected for transcriptome profiling based on their rachis brittleness and glumes toughness. RNA pools from glumes of the central spikelet at heading time were used to construct cDNA libraries for sequencing. The trimmed reads from each library were separately aligned to the reference sub-genomes A and B, which were extracted from wheat survey sequence. Differentially expression analysis and functional annotation were performed between wild and domesticated wheat, to identity candidate genes associated with evolution under domestication. Selected candidate genes were validated using real time PCR. Results: Transcriptome profiles of wild emmer wheat, wheat landraces, and wheat cultivars were compared using next generation sequencing (RNA-seq). We have found a total of 194,893 transcripts, of which 73,150 were shared between wild, landraces, and cultivars. From 781 differentially expressed genes (DEGs), 336 were down-regulated and 445 were up-regulated in the domesticated compared to wild wheat genotypes. Gene Ontology (GO) annotation assigned 293 DEGs (37.5 %) to GO term groups, of which 134 (17.1 %) were down-regulated and 159 (20.4 %) up-regulated in the domesticated wheat. Some of the down-regulated DEGs in domesticated wheat are related to the biosynthetic pathways that eventually define the mechanical strength of the glumes, such as cell wall, lignin, pectin and wax biosynthesis. The reduction in gene expression of such genes, may explain the softness of the glumes in the domesticated forms. In addition, we have identified genes involved in nutrient remobilization that may affect grain size and other agronomic traits evolved under domestication. Conclusions: The comparison of RNA-seq profiles between glumes of wheat groups differing in glumes toughness and rachis brittleness revealed a few DEGs that may be involved in glumes toughness and nutrient remobilization. These genes may be involved in processes of wheat improvement under domestication. © 2015 Zou et al.
Combined correlation-based network and mQTL analyses efficiently identified loci for branched-chain amino acid, serine to threonine, and proline metabolism in tomato seeds
. Plant Journal 2015
, 121-133. Publisher's VersionAbstract
Correlation-based network analysis (CNA) of the metabolic profiles of seeds of a tomato introgression line mapping population revealed a clique of proteinogenic amino acids: Gly, Ile, Pro, Ser, Thr, and Val. Correlations between profiles of these amino acids exhibited a statistically significant average correlation coefficient of 0.84 as compared with an average correlation coefficient of 0.39 over the 16 119 other metabolite cliques containing six metabolites. In silico removal of cliques was used to quantify their importance in determining seminal network properties, highlighting the strong effects of the amino acid clique. Quantitative trait locus analysis revealed co-localization for the six amino acids on chromosome 2, 4 and 10. Sequence analysis identified a unique set of 10 genes on chromosome 2 only, which were associated with amino acid metabolism and specifically the metabolism of Ser-Gly and their conversion into branched-chain amino acids. Metabolite profiling of a set of sublines, with introgressions on chromosome 2, identified a significant change in the abundance of the six amino acids in comparison with M82. Expression analysis of candidate genes affecting Ser metabolism matched the observation from the metabolite data, suggesting a coordinated behavior of the level of these amino acids at the genetic level. Analysis of transcription factor binding sites in the promoter regions of the identified genes suggested combinatorial response to light and the circadian clock. Significance Statement In the current study we have effectively identified loci for branched chain amino acid, serene, glycine, threonine and proline metabolism for seeds of a tomato Introgression Line mapping population. We did so by applying a combined correlation based network approach with quantitative trait locus mapping. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.
Domestication selected for deceleration of the circadian clock in cultivated tomato
. Nature Genetics 2015
, 89-93. Publisher's VersionAbstract
The circadian clock is a critical regulator of plant physiology and development, controlling key agricultural traits in crop plants. In addition, natural variation in circadian rhythms is important for local adaptation. However, quantitative modulation of circadian rhythms due to artificial selection has not yet been reported. Here we show that the circadian clock of cultivated tomato (Solanum lycopersicum) has slowed during domestication. Allelic variation of the tomato homolog of the Arabidopsis gene EID1 is responsible for a phase delay. Notably, the genomic region harboring EID1 shows signatures of a selective sweep. We find that the EID1 allele in cultivated tomatoes enhances plant performance specifically under long day photoperiods, suggesting that humans selected slower circadian rhythms to adapt the cultivated species to the long summer days it encountered as it was moved away from the equator. © 2016 Nature America, Inc.
Identification and mode of inheritance of quantitative trait loci for secondary metabolite abundance in tomato
. Plant Cell 2015
, 485-512. Publisher's VersionAbstract
A large-scale metabolic quantitative trait loci (mQTL) analysis was performed on the well-characterized Solanum pennellii introgression lines to investigate the genomic regions associated with secondary metabolism in tomato fruit pericarp. In total, 679 mQTLs were detected across the 76 introgression lines. Heritability analyses revealed that mQTLs of secondary metabolism were less affected by environment than mQTLs of primary metabolism. Network analysis allowed us to assess the interconnectivity of primary and secondary metabolism as well as to compare and contrast their respective associations with morphological traits. Additionally, we applied a recently established real-time quantitative PCR platform to gain insight into transcriptional control mechanisms of a subset of the mQTLs, including those for hydroxycinnamates, acyl-sugar, naringenin chalcone, and a range of glycoalkaloids. Intriguingly, many of these compounds displayed a dominant-negative mode of inheritance, which is contrary to the conventional wisdom that secondary metabolite contents decreased on domestication. We additionally performed an exemplary evaluation of two candidate genes for glycolalkaloid mQTLs via the use of virus-induced gene silencing. The combined data of this study were compared with previous results on primary metabolism obtained from the same material and to other studies of natural variance of secondary metabolism. © 2015 American Society of Plant Biologists. All rights reserved.
Towards the rose genome sequence and its use in research and breeding
. Acta Horticulturae 2015
, 167-175. Publisher's VersionAbstract
Rose is one of the most economically important ornamental crops worldwide. Rosa sp. can become a model for woody ornamentals. Its genome size is relatively small (560 Mb), its genetic history with ploïdy events is well documented, and rose has a short life for a woody plant. Furthermore, different tools are available, including transcriptomic tools, genetic maps and genetic transformation protocols. Rose represents an original model for studying some ornamental traits that cannot be addressed in other model plant species such as Arabidopsis. Some of these traits, such recurrent blooming, flower morphogenesis or scent production and emission, are of economic interest. Different groups involved in rose genetics and genomics gathered to form the 'Rose Genome Sequence Initiative'. Our objective is to obtain a high quality rose genome sequence of the diploid R. chinensis 'Old Blush'. One important issue is the high level of heterozygosity of roses. To tackle this issue, different strategies are proposed: production of a haploid and development a high density genetic map to anchor the genome. This genetic map will be developed from a cross between 'Old Blush' and R. wichurana. The genotype R. chinensis 'Old Blush' will be sequenced using NGS technologies. The data will be assembled and arranged using the high-density map. In order to increase ESTs and to facilitate genome annotation, we have recently produced ESTs from various tissues of 'Old Blush' under different conditions. Digital expression (RNA Seq) was obtained from the different tissues and data are available on the following web site (https://iant.toulouse.inra.fr/plants/rosa/FATAL/
). The rose genome sequence will be a great step to help identifying the molecular basis of ornamental traits and also to study genetic diversity and genome evolution in the genus Rosa and in the Rosaceae family. © 2015, International Society for Horticultural Science. All rights reserved.
Adventitious root primordia formation and development in stem nodes of ‘Georgia jet’ sweetpotato, Ipomoea batatas
. American Journal of Botany 2015
, 1040-1049. Publisher's VersionAbstract
PREMISE OF THE STUDY: Yield in sweetpotato is determined by the number of storage roots produced per plant. Storage roots develop from adventitious roots (ARs) present in stem cuttings that serve as propagation material. Data on the origin of sweetpotato ARs and the effect of nodal position on AR establishment and further development are limited. METHODS: We anatomically described root primordium initiation using stem sections and measured number of root primordia formed at different nodal positions using light microscopy and correlated nodal positions with AR number and length 14 d after planting (DAP). KEY RESULTS: Primordia for ARs initiate at the junction of the stem pith ray and the cambium, on both sides of the leaf gap, and they are well developed before emerging from the stem. The number of ARs that develop from isolated stem nodes 14 DAP corresponded to the number of AR primordia detected inside the stem. The total length of established roots at nodes 9-13 from the apex is about 2-fold longer than at nodes 5-8. CONCLUSIONS: Nodal position (age) has a significant effect on the developmental status and number of root primordia inside the stem, determining the number and length of ARs that have developed by 14 DAP. Adventitious roots originating from nodes 9-13 possess similar AR systems and develop better than those originating from younger nodes 3-8. The mechanism regulating AR initiation in nodes is discussed. This system can serve for studying the effect of environmental conditions on AR initiation, development, and capacity to form storage roots. © 2015 Botanical Society of America.
Direct in vivo evidence of immense stem water exploitation in irrigated date palms
. Journal of Experimental Botany 2015
, 333-338. Publisher's VersionAbstract
During the summer, evaporative demand at midday often exceeds the transport capacity of most desert plants. However, date palms maintain their ecological dominance with sustained and uniquely high rates of transpiration. This high rate of flow cannot be attributed to soil water supply alone. In order to quantify intra-plant water allocation in irrigated date palms, three water-sensing techniques have been incorporated: heat dissipation, gravimetric sampling, and time domain reflectrometry. Each of these methods has known limitations but their integration resulted in a quantitative in vivo accounting of the date palm diurnal and seasonal water mass balance. By incorporating these methods it was possible to determine that date palms substantially rely on the exploitation and recharge of the stem reservoir in their water budget. The stem of mature date palms can hold up to 1 m3 of water and supply 25% of daily transpiration (i.e. 5000 l of water in 100 d of summer). The internal stem water reservoir is consistently recharged by over 50 l per night which allows for successive daytime reuse throughout the entire growing season. More broadly, these findings suggest that internal water allocation and night-time soil-water availability could provide useful information for improving date palm irrigation practices. © The Author 2014.
Grapevine anatomy as a possible determinant of isohydric or anisohydric behavior
. American Journal of Enology and Viticulture 2015
, 340-347. Publisher's VersionAbstract
Isohydric plants maintain constant water potential through rapid stomatal closure, whereas anisohydric plants only close their stomata at very low water potentials. However, distinctions between isohydric and anisohydric behaviors among different cultivars of the same species are unclear. This study compared the physiological response to prolonged drought stress in the isohydric Grenache and the anisohydric Shiraz cultivars of the Vitis vinifera species. Plants were exposed to 60-day periods of deficit irrigation (25% of plant water consumption under well-watered conditions) during the summers of 2011 and 2012. Physiological measurements, water potential, leaf gas exchange, canopy area, leaf senescence, stem characteristics, and morphological characteristics were analyzed. Stomatal conductance was consistently lower in Grenache than in Shiraz at all values of midday stem and predawn leaf water potentials, respectively. The Shiraz plants exhibited greater vegetative growth and less defoliation than the Grenache plants in response to water deficit. Anatomical architecture analyses revealed that Grenache plants had greater xylem vessel diameter, hydraulic conductivity, and stomatal density than the Shiraz plants. These results suggest isohydric and anisohydric behaviors may be well-defined, time-regulated responses rather than distinct mechanisms that plants use to cope with drought stress. The rapid response to water deficit exhibited by isohydric plants may be because they are more vulnerable to fatal xylem embolisms than anisohydric plants. Thus, the accelerated response allows isohydric plants to avoid drought stress and minimize risk of xylem cavitation, but may lower the plant’s ability to survive moderate stress of prolonged drought. © 2015 by the American Society for Enology and Viticulture. All rights reserved.
Modification of non-stomatal limitation and photoprotection due to K and Na nutrition of olive trees
. Journal of Plant Physiology 2015
, 1-10. Publisher's VersionAbstract
Potassium (K) is an essential macronutrient shown to play a fundamental role in photosynthetic processes and may facilitate photoinhibition resistance. In some plant species, sodium (Na) can partially substitute for K. Although photosynthetic enhancement has been well established, the mechanisms by which K or Na affects photosynthesis are not fully understood. Olive (Olea europaea L.) trees were previously shown to benefit from Na nutrition when K is limiting. In order to study the effect of K and Na on photosynthetic performance, we measured gas exchange and chlorophyll fluorescence in young olive trees supplied with either K, Na or no fertilizer, and subjected to manipulated levels of CO2, O2 and radiation. Light and CO2 response curves indicate substantially superior photosynthetic capacity of K-sufficient trees, while Na substitution generated intermediate results. The enhanced performance of K, and to a lesser extent, Na-supplied trees was found to be related mainly to modification of non-stomatal limitation. This indicates that K deficiency promotes inhibition of enzymatic-photochemical processes. Results indicate lower chlorophyll content and altered Rubisco activity as probable causes of photosynthetic impairment. Potassium deficiency was found to diminish photoprotection mechanisms due to reduced photosynthetic and photorespiratory capacity. The lower CO2 and O2 assimilation rate in K-deficient trees caused elevated levels of exited energy. Consequently, non-photochemical quenching, an alternative energy dispersion pathway, was increased. Nonetheless, K-deficient trees were shown to suffer from photodamage to photosystem-II. Sodium replacement considerably diminished the negative effect of K deficiency on photoprotection mechanisms. The overall impact of K and Na nutrition plays down any indirect effect on stomatal limitation and rather demonstrates the centrality of these elements in photochemical processes of photosynthesis and photoprotection. © 2015 Elsevier GmbH.
Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells
. Journal of Experimental Botany 2015
, 1355-1368. Publisher's VersionAbstract
In vivo changes in the cytosolic pH of abscission zone (AZ) cells were visualized using confocal microscopic detection of the fluorescent pH-sensitive and intracellularly trapped dye, 2',7'-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), driven by its acetoxymethyl ester. A specific and gradual increase in the cytosolic pH of AZ cells was observed during natural abscission of flower organs in Arabidopsis thaliana and wild rocket (Diplotaxis tenuifolia), and during flower pedicel abscission induced by flower removal in tomato (Solanum lycopersicum Mill). The alkalization pattern in the first two species paralleled the acceleration or inhibition of flower organ abscission induced by ethylene or its inhibitor 1-methylcyclopropene (1-MCP), respectively. Similarly, 1-MCP pre-treatment of tomato inflorescence explants abolished the pH increase in AZ cells and pedicel abscission induced by flower removal. Examination of the pH changes in the AZ cells of Arabidopsis mutants defective in both ethylene-induced (ctr1, ein2, eto4) and ethylene-independent (ida, nev7, dab5) abscission pathways confirmed these results. The data indicate that the pH changes in the AZ cells are part of both the ethylene-sensitive and -insensitive abscission pathways, and occur concomitantly with the execution of organ abscission. pH can affect enzymatic activities and/or act as a signal for gene expression. Changes in pH during abscission could occur via regulation of transporters in AZ cells, which might affect cytosolic pH. Indeed, four genes associated with pH regulation, vacuolar H+-ATPase, putative high-affinity nitrate transporter, and two GTP-binding proteins, were specifically up-regulated in tomato flower AZ following abscission induction, and 1-MCP reduced or abolished the increased expression. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.
Ethylene extends the vase life of Dodonaea 'Dana' cut branches: Possible mechanisms
. Acta Horticulturae 2015
, 279-286. Publisher's VersionAbstract
Dodonaea 'Dana' is an Israeli hybrid of Dodonaea viscosa L. 'Purpurea' and Dodonaea lobulata (Sapindaceae), characterized by purple tinted decorative foliage and fruits. Cut Dodonaea branches showed seasonal variations in vase life longevity, wilting after one week in winter, and having a vase life of three weeks in summer. The wilting phenomenon resulted from improper water conductance, caused by temperature-induced seasonal anatomical changes. Exposure of cut branches to ethylene (0.5-10 μL L-1, 24 h) improved their longevity in a concentration-dependent manner, expressed in the absence of leaf wilting and a significant increase in fresh weight (FW) during 12 days. Application of the ethylene inhibitor 1-methylcyclopropene (1-MCP) (0.05-0.2 μL L-1, 4 h) resulted in opposite effects. Ethylene improved water uptake of cut branches but did not affect the transpiration rate or the leaf relative water content (RWC), suggesting that the increased FW might have resulted from new growth. Indeed, a significant ethylene-enhanced increase in both elongation and widening dimensions was observed only in immature leaves (3-to 5.5-cm-long), but not in mature leaves (7.5-to 11-cm-long). The aquaporin inhibitor, phloretin, which reduced the branch FW and leaf size, completely abolished the ethylene-induced increase in branch FW and leaf size, suggesting that the positive response of the cut branches and young leaves to ethylene might involve phloretinsensitive aquaporins. The data suggest that the ethylene-induced increase in FW of cut Dodonaea branches is related to young leaf growth and water flow, which seem to be mediated by the activity of aquaporins.
Role of auxin depletion in abscission control
. Stewart Postharvest Review 2015
. Publisher's VersionAbstract
Purpose of review: Abscission is a programmed developmental process initiated by auxin depletion. This review summarizes the mechanisms leading to auxin depletion in the abscission zone (AZ), evaluates the methods for estimation of the spatio-temporal auxin levels, demonstrates how auxin depletion occurs during natural, stressinduced, and artificially-induced organ abscission, and presents new evidence for early and late events resulting from auxin depletion which lead to organ abscission. Findings: Auxin depletion occurs during natural developmental processes which end in organ abscission (leaf and flower senescence, fruit ripening, and self-pruning) and stress-induced abscission, and following artificial organ removal in the tomato model system. Stress-induced auxin depletion is mediated by increased ethylene and reactive oxygen species (ROS) production and carbohydrate starvation. Similar changes in auxin-related genes occurred in both flower AZ (FAZ) and leaf AZ (LAZ) following flower or leaf removal, respectively, suggesting a similar regulation of the abscission process of these organs. Auxin depletion resulted from decreased indole-3- acetic acid (IAA) biosynthesis and transport, as well as from enhanced IAA transport autoinhibition (ATA), conjugation and oxidative IAA catabolism. Functional analyses of several target genes delaying abscission, such as Knotted- Like Homeobox Protein1 (KD1), Tomato Proline Rich Protein (TPRP), Ethylene Responsive Factor52 (ERF52), and Ribonuclease LX (LX), shed light on various events operating in response to auxin depletion in tomato FAZ and/or LAZ. The information gained allows a better understanding of the abscission process driven by auxin depletion, and might lead to development of improved methods for abscission control in horticultural crops. Direction for future research: A better understanding of abscission regulation as it pertains to auxin depletion will require advanced molecular tools such as microarrays, new generation sequencing (NGS), transcriptomic, functional, and proteomic analyses of target genes and proteins found to operate in the abscission process. © 2015 SPS (UK) Ltd.
Rhythmic leaf movements: Physiological and molecular aspects
; Rhythms in Plants: Dynamic Responses in a Dynamic Environment; 2015; pp. 57-95. Publisher's VersionAbstract
Daily periodic plant leaf movements, known since antiquity, are dramatic manifestations of “osmotic motors” regulated by the endogenous biological clock and by light, perceived by phytochrome and, possibly, by phototropins. Both the reversible movements and their regulation usually occur in specialized motor leaf organs, pulvini. The movements result from opposing volume changes in two oppositely positioned parts of the pulvinus. Water fluxes into the motor cells in the swelling part and out of the motor cells in the concomitantly shrinking part are powered by ion fluxes into and out of these cells, and all of these fluxes occur through tightly regulated membranal proteins: Pumps, carriers, and ion and water channels. This chapter attempts to piece together those findings and insights about this mechanism which have accumulated during the past two and a half decades. © Springer International Publishing Switzerland 2006, 2015.
Effects of the 3D sizing of polyacrylonitrile fabric with carbon nanotube–SP1 protein complex on the interfacial properties of polyacrylonitrile/phenolic composites
. Journal of Composite MaterialsJournal of Composite Materials 2015
, 1031 - 1036. Publisher's VersionAbstract
Polyacrylonitrile?phenolic composites display excellent in-plane properties but perform poorly when out-of-plane, through-thickness properties are considered. Composite architectures with carbon nanotubes, either dispersed within the matrix or bound to a fabric, in traditional composites have the potential to alleviate this weakness. However, effective reinforcement of composites using carbon nanotubes is difficult, due to poor dispersion and interfacial stress transfer and has thus far been met with limited success and at high costs. This paper describes an innovative and cost-effective technology to improve these inferior mechanical properties by using an exceptionally stable protein, SP1, for CNT attachment to PAN fabric, forming a three-dimensional nano-reinforced structure. This work confirms remarkable improvements in interlaminar shear strength and through-thickness tensile strength of SP1/CNT-reinforced polyacrylonitrile composites.
The ERECTA, CLAVATA and class III HD-ZIP Pathways Display Synergistic Interactions in Regulating Floral Meristem Activities. PLoS One 2015
In angiosperms, the production of flowers marks the beginning of the reproductive phase. At the emergence of flower primordia on the flanks of the inflorescence meristem, the WUSCHEL (WUS) gene, which encodes a homeodomain transcription factor starts to be expressed and establishes de novo stem cell population, founder of the floral meristem (FM). Similarly to the shoot apical meristem a precise spatial and temporal expression pattern of WUS is required and maintained through strict regulation by multiple regulatory inputs to maintain stem cell homeostasis. However, following the formation of a genetically determined fixed number of floral organs, this homeostasis is shifted towards organogenesis and the FM is terminated. In here we performed a genetic study to test how a reduction in ERECTA, CLAVATA and class III HD-ZIP pathways affects floral meristem activity and flower development. We revealed strong synergistic phenotypes of extra flower number, supernumerary whorls, total loss of determinacy and extreme enlargement of the meristem as compared to any double mutant combination indicating that the three pathways, CLV3, ER and HD-ZIPIII distinctively regulate meristem activity and that they act in parallel. Our findings yield several new insights into stem cell-driven development. We demonstrate the crucial requirement for coupling floral meristem termination with carpel formation to ensure successful reproduction in plants. We also show how regulation of meristem size and alternation in spatial structure of the meristem serve as a mechanism to determine flower organogenesis. We propose that the loss of FM determinacy due to the reduction in CLV3, ER and HD-ZIPIII activity is genetically separable from the AGAMOUS core mechanism of meristem termination.