Project description: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.

Project description:Six months old seed grown under well-watered greenhouse conditions were used in the current study. The seedlings of the two wild emmer wheat genotypes were vernalized on a moist germination paper (Hofman Manufacturing, Inc, Jefferson, OR, USA) for three weeks in the dark at 4oC, followed by three days acclimation at 24oC. Seedlings were then transplanted into 5L pots containing a mixture of pure quartz sand and peat (4:1 v/v), supplemented with a slow release fertilizer (2 g/L, Osmocote® Standard 14-14-14, Scotts-Sierra Horticulture, Marysville, OH, USA) and by a weekly application of 100 ml/pot of 0.5X Murashigi and Skoog growth solution (Sigma Chemical Co., St Louis, MO, USA). Pots were placed in a screen-house under natural winter conditions (December to February; 5-18°C) in Haifa, Israel (Mt. Carmel; 35o01′ E, 32o45′ N; 480 m above sea level) for 10 weeks and irrigated daily by a drip irrigation system. Three weeks prior to application of terminal drought stress, the pots were transferred to a controlled environment greenhouse (22/18 oC; 12 h day/12 h night) in order to prevent rainfall during the drought experiment. Five pots per genotype served as biological replicates, plants of three pots of each genotype/treatment were used for transcriptome study whereas two additional pots were used for quantitative PCR analysis (altogether five biological replicated of were used for quantitative real time PCR). Three individual plants were grown in each pot, one plant was used for measurements of leaf relative water content (RWC) (Barrs and Weatherley 1968), whereas the other two plants were used for sampling of flag leaf tissue for RNA extraction. Terminal drought stress (D) was applied at inflorescence emergence stage (Zadoks 50-60), (Zadoks et al. 1974), after emergence of 1-2 spikes in all biological replicates of both genotypes. The time from transplanting to inflorescence emergence stage was not significantly different between genotypes (70 days in the S genotype and 72 days in the R genotype). Drought stress application initiated after irrigation with excess amount of water in order to assure that all pots start the experiment at the same soil water capacity. Drought stress was imposed by withholding water for eight days until stress symptoms (i.e. leaf rolling and wilting symptoms) were visible in plants of both genotypes. Stress symptoms were more visible in the S genotype, however, leaf relative water content (RWC), measured after eight days of drought stress was low but was not significantly different between the two genotypes (49.68%±1.48 in the R genotype and 53.34%±1.83 in the S genotype). The well-watered control (C) plants were irrigated daily by ample amount of water. Flag leaf tissues of drought-stressed plants and well-watered control plants were harvested, immediately frozen in liquid nitrogen, and stored at -80ºC for RNA extraction. ****[PLEXdb(http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Krugman Tamar. The equivalent experiment is TA33 at PLEXdb.]

Project description:Six months old seed grown under well-watered greenhouse conditions were used in the current study. The seedlings of the two wild emmer wheat genotypes were vernalized on a moist germination paper (Hofman Manufacturing, Inc, Jefferson, OR, USA) for three weeks in the dark at 4oC, followed by three days acclimation at 24oC. Seedlings were then transplanted into 5L pots containing a mixture of pure quartz sand and peat (4:1 v/v), supplemented with a slow release fertilizer (2 g/L, Osmocote® Standard 14-14-14, Scotts-Sierra Horticulture, Marysville, OH, USA) and by a weekly application of 100 ml/pot of 0.5X Murashigi and Skoog growth solution (Sigma Chemical Co., St Louis, MO, USA). Pots were placed in a screen-house under natural winter conditions (December to February; 5-18°C) in Haifa, Israel (Mt. Carmel; 35o01′ E, 32o45′ N; 480 m above sea level) for 10 weeks and irrigated daily by a drip irrigation system. Three weeks prior to application of terminal drought stress, the pots were transferred to a controlled environment greenhouse (22/18 oC; 12 h day/12 h night) in order to prevent rainfall during the drought experiment. Five pots per genotype served as biological replicates, plants of three pots of each genotype/treatment were used for transcriptome study whereas two additional pots were used for quantitative PCR analysis (altogether five biological replicated of were used for quantitative real time PCR). Three individual plants were grown in each pot, one plant was used for measurements of leaf relative water content (RWC) (Barrs and Weatherley 1968), whereas the other two plants were used for sampling of flag leaf tissue for RNA extraction. Terminal drought stress (D) was applied at inflorescence emergence stage (Zadoks 50-60), (Zadoks et al. 1974), after emergence of 1-2 spikes in all biological replicates of both genotypes. The time from transplanting to inflorescence emergence stage was not significantly different between genotypes (70 days in the S genotype and 72 days in the R genotype). Drought stress application initiated after irrigation with excess amount of water in order to assure that all pots start the experiment at the same soil water capacity. Drought stress was imposed by withholding water for eight days until stress symptoms (i.e. leaf rolling and wilting symptoms) were visible in plants of both genotypes. Stress symptoms were more visible in the S genotype, however, leaf relative water content (RWC), measured after eight days of drought stress was low but was not significantly different between the two genotypes (49.68%±1.48 in the R genotype and 53.34%±1.83 in the S genotype). The well-watered control (C) plants were irrigated daily by ample amount of water. Flag leaf tissues of drought-stressed plants and well-watered control plants were harvested, immediately frozen in liquid nitrogen, and stored at -80ºC for RNA extraction. ****[PLEXdb(http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Krugman Tamar. The equivalent experiment is TA33 at PLEXdb.] genotype: Drought resistant (R) Y12-3 - treated or untreated: Well-watered(3-replications); genotype: Drought resistant (R) Y12-3 - treated or untreated: terminal drought(3-replications); genotype: Drought susceptible (S) A24-39 - treated or untreated: Well-watered(3-replications); genotype: Drought susceptible (S) A24-39 - treated or untreated: terminal drought(3-replications)

Project description:Background and aimsMicronutrient malnutrition, particularly zinc and iron deficiency, afflicts over three billion people worldwide due to low dietary intake. In the current study, wild emmer wheat (Triticum turgidum ssp. dicoccoides), the progenitor of domesticated wheat, was tested for (1) genetic diversity in grain nutrient concentrations, (2) associations among grain nutrients and their relationships with plant productivity, and (3) the association of grain nutrients with the eco-geographical origin of wild emmer accessions.MethodsA total of 154 genotypes, including wild emmer accessions from across the Near Eastern Fertile Crescent and diverse wheat cultivars, were characterized in this 2-year field study for grain protein, micronutrient (zinc, iron, copper and manganese) and macronutrient (calcium, magnesium, potassium, phosphorus and sulphur) concentrations.Key resultsWide genetic diversity was found among the wild emmer accessions for all grain nutrients. The concentrations of grain zinc, iron and protein in wild accessions were about two-fold greater than in the domesticated genotypes. Concentrations of these compounds were positively correlated with one another, with no clear association with plant productivity, suggesting that all three nutrients can be improved concurrently with no yield penalty. A subset of 12 populations revealed significant genetic variation between and within populations for all minerals. Association between soil characteristics at the site of collection and grain nutrient concentrations showed negative associations between soil clay content and grain protein and between soil-extractable zinc and grain zinc, the latter suggesting that the greatest potential for grain nutrient minerals lies in populations from micronutrient-deficient soils.ConclusionsWild emmer wheat germplasm offers unique opportunities to exploit favourable alleles for grain nutrient properties that were excluded from the domesticated wheat gene pool.

Dataset Information

Ancestral QTL Alleles from Wild Emmer Wheat Improve Drought Resistance and Productivity in Modern Wheat Cultivars.

Publications

Ancestral QTL Alleles from Wild Emmer Wheat Improve Drought Resistance and Productivity in Modern Wheat Cultivars.

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