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Chromosome Pairing and Fertility in Polyploids
Published in Christopher B. Gillies, Fertility and Chromosome Pairing: Recent Studies in Plants and Animals, 2020
Some support for this theory seemed to come from the results of Bennett and Kaltsikes,183 who found that meiotic and prophase I times in diploid rye, tetraploid and hexaploid wheat, and hexaploid triticale were all different. This could result in a time limit for pairing in hybrids, and affect meiotic stability. However, subsequent studies in hexaploid wheat aneuploids showed that the duration of meiosis was not correlated with the amount of homoeologous pairing.196 An effect of nullisomic 5B was shown to be due to 5BS. Thus, if the Ph gene affected pairing times, it did not alter total meiotic duration.
Atlas of Autofluorescence in Plant Pharmaceutical Materials
Published in Victoria Vladimirovna Roshchina, Fluorescence of Living Plant Cells for Phytomedicine Preparations, 2020
Victoria Vladimirovna Roshchina
Bright blue fluorescence due to sesquiterpene lactones and monoterpenes such as menthol predominated in the flower petals and leaves, which contain sesquiterpenoids (up to 1% of the essential oil, which includes about 30% azulenes, as well as the alkaloid achillein (Murav’eva et al. 2007). The fluorescence spectrum of crystalline azulene, which emits with maximum 430 nm, is shown in Figure 3.2. According to Murav’eva and coauthors (2007), secretory glands are fulfill of chamazulene (also fluorescing in blue at 420–435 nm), which may be transformed into the bitter prochamazulene achillicine. Diploid and tetraploid plants contain proazulene sesquiterpenes that are transformed into colored azulenes, including chamazulene (up to 25%) and achillicine. Amount of carotene also differs, but it weakly fluoresces upon contact with water (van Riel et al. 1983). Hexaploid plants are azulene sesquiterpene free. It should be noted that unlike leaf secretory cells, in petals, there is no chlorophyll in the glands, but some azulenes bound to cellulose in cell walls may also give red (maximum 620 nm) emission (Roshchina et al. 1995). Perhaps, some flavonoids (anthocyanins) and coumarins may contribute to the blue-green fluorescence (Roshchina 2003, 2008; Roshchina et al. 2011).
rDNA: Evolution Over a Billion Years
Published in S. K. Dutta, DNA Systematics, 2019
The rRNA genes of wheat (T. aestivum cv. Chinese Spring) are located mainly on chromosomes 1B and 6B with a minor site located on chromosome 5D81,82 (Figure 5). Although the rDNA is located in the distal one half to one third of the respective chromosomes, the genetic distance (determined by recombination frequency of the rDNA) from the centromere is very small (6B examined in detail83). Estimates for the numbers of rRNA genes on chromosome 1B range from 1300 to 1500, 6B from 500 to 3000, and 5D from 130 to 400 depending on the wheat variety considered.84,438 In T. aestivum cv. Chinese Spring there are no detectable rRNA genes on chromosome 1A,81 although in T. aestivim ssp. spelta this chromosome is a major location for rRNA genes.85 Quantitative variation in rRNA gene numbers in wheat and related grasses is also evident from heterozygosity observed in situ hybridization experiments using radioactive probes, where grain counts consistently indicate differences between homologous sites.85 Within the genus Triticum, most diploid and tetraploid species have two chromosomal locations for rDNA,86,89 and in specific cases such as T. araraticum,90T. dicoccoides,91 and T. speltoides92 these sites have been designated 1B and 6B. The homologous group 5 chromosomes also carry ribosomal DNA in some diploid Triticum species.89,92 Among hexaploid wheats as many as four chromosomal locations have been found.87
Evaluation of the genetic structure of Bromus inermis populations from chemically and radioactively polluted areas using microsatellite markers from closely related species
Published in International Journal of Radiation Biology, 2022
Elena V. Antonova, Marion S. Röder
The awnless brome (smooth brome, Russian bromegrass, Bromopsis inermis Leyss. = Bromus inermis Leyss., ITIS No. 40502), is a polymorphic species of the Poaceae family (Williams et al. 2011). Bromus inermis is widespread in different climatic areas of Europe, Asia and America (Bánki et al. 2021). It is a perennial, polycarpic, valuable forage plant, widely used in grassland and field grass cultivation, as well as in the fight against soil erosion (Himmelbauer et al. 2009). For this species, octoploid (genome AAAAB1B1B2B2, 2n=8x=56), hexaploid (2n=6x=42), and tetraploid (AABB, 2n=4x=28) forms have been described (Tuna et al. 2004). According to our data (Antonova et al. 2020), the studied brome populations are represented by octoploids.
Echinacea biotechnology: advances, commercialization and future considerations
Published in Pharmaceutical Biology, 2018
Jessica L. Parsons, Stewart I. Cameron, Cory S. Harris, Myron L. Smith
Likewise, the manipulation of ploidy can cause changes to morphology and phytochemical content of plants. Naturally occurring polyploids are commonly used in agriculture and widely accepted by the public. Triploid, tetraploid and hexaploid Echinacea plants have been developed, with tetraploids (4× = 44) being the best studied. In comparison to wild-type diploids, the tetraploids studied have altered leaf, root, and flower morphology, reduced seed set and dwarfed phenotypes (Nilanthi et al. 2009; Koul et al. 2010; Abdoli et al. 2013; Xu et al. 2014; Chen et al. 2016). Tetraploid plants have similar phytochemical profiles to wild types, but they consistently yield higher levels of CADs, particularly in the leaves. Increased alkylamide content in the leaves and roots of tetraploids has also been noted (Koul et al. 2010; Abdoli et al. 2013; Xu et al. 2014). The reduced biomass production due to polyploid dwarf phenotypes currently makes ploidy manipulation an impractical way to improve the quality of Echinacea plant material. However, supplementing culture media with 0.3 mg/L IBA can accelerate the emergence of roots and the increased rooting rate of tetraploid shoots in vitro whereas IBA has no positive effect on cultured haploid or diploid shoots (Chen et al. 2016).
Challenges to drug discovery for celiac disease and approaches to overcome them
Published in Expert Opinion on Drug Discovery, 2019
Luis Vaquero, David Bernardo, Francisco León, Laura Rodríguez-Martín, Begoña Alvarez-Cuenllas, Santiago Vivas
One possibility is the selection of wheat strains with a reduced content of immunogenic epitopes, such as hexaploid strains generated from diploid and tetraploid species more than 1000 years ago. It has been shown that these strains confer immunogenicity and have a lower percentage of α¸ β¸ γ¸ and ω gliadins. Psyllium [70] is an alternative to gluten because it has a minimal effect on the smell and texture of wheat and good cooking properties [71]. Bread made with psyllium is appreciated by both patients with CD and healthy individuals for its texture and flavor. Another alternative is the use of genetic engineering, via RNA interference, to silence genes that encode immunogenic epitopes [72]. Recent studies evaluated the silencing of the HMW-G gene in a transgenic wheat strain (Bobwhite) and found that the content of wet gluten and the period of crop development were decreased. Gene silencing is an alternative to the production of gluten-free products [73]. Other studies have performed genetic modifications in wheat with the deletion of essential gliadin genes. The deletion of the α-gliadin locus on chromosome 6 in a hexaploid strain of wheat (Triticum aestivum) decreased the number of immunogenic epitopes recognized by T-cells, but did not significantly affect the cooking properties [74]. The deleted gliadin genes may need to be replaced with non-immunogenic gliadin or avenin genes to improve dough elasticity. The transgenic wheat strain E82 has been used in patients with non-celiac gluten sensitivity with undetectable immunogenic peptides in feces, and the good tolerability and high acceptance of the bread characteristics of this strain have been presented [75]; this method is pending evaluation in patients with CD to confirm these promising results.