Heterogeneous pollen in Chlorophytum comosum, a species with a unique mode of plastid inheritance intermediate between the maternal and biparental modes.
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The majority of angiosperms display maternal plastid inheritance. The cytological mechanisms of this mode of inheritance have been well studied, but little is known about its genetic relationship to biparental inheritance. The angiosperm Chlorophytum comosum is unusual in that different pollen grains show traits of different modes of plastid inheritance. About 50% of these pollen grains exhibit the potential for biparental plastid inheritance, whereas the rest exhibit maternal plastid inheritance. There is no morphological difference between these two types of pollen. Pollen grains from different individuals of C. comosum all exhibited this variability. Closer examination revealed that plastid polarization occurs, with plastids being excluded from the generative cell during the first pollen mitosis. However, the exclusion is incomplete in 50% of the pollen grains, and the few plastids distributed to the generative cells divide actively after mitosis. Immunoelectron microscopy using an anti-DNA antibody demonstrated that the plastids contain a large amount of DNA. As there is a considerable discrepancy between the exclusion and duplication of plastids, resulting in plastids with opposite fates occurring simultaneously in C. comosum, we propose that the species is a transitional type with a mode of plastid inheritance that is genetically intermediate between the maternal and biparental modes. (+info)
In situ chromosomal localization of rDNA sites in "Safed Musli" Chlorophytum ker-gawl and their physical measurement by fiber FISH.
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Fluorescence In Situ Hybridization (FISH) technique has been applied on somatic chromosomes and extended DNA fibers in the medicinally important species of Chlorophytum to elucidate physical localization and measurement of the rDNA sites using two rRNA multigene families homologous to 45S and 5S rDNA. The two species of Chlorophytum, namely C. borivillianum and C. comosum, both with 2n = 28, reveal diversity for copy number and localization of rDNA sites. C. borivillianum is comprised of five 45S-rDNA sites:one each in the secondary constriction region of chromosomes 7, 8, 9; one in the subtelomeric region of the short arm of chromosome 2 and the telomeric region of the short arm of chromosome 12; and one 5S-rDNA site in the subtelomeric region of the long arm of chromosome 1. In C. comosum, there are three 45S-rDNA sites (one each in the short arm of chromosomes 12, 13, and 14) and two 5S-rDNA sites (in the secondary constriction regions of chromosomes 2 and 13). Fiber FISH analysis conducted on extended DNA fibers revealed variation in the size of continuous tandem strings for the two r-DNA families. Taking the standard value of native B DNA equivalent to 3.27 kb for 1 mum, it was estimated that the physical size of continuous DNA strings is of the order of approximately 90 kb, 180 kb, and 300 kb for 45S-rDNA and of the order of 60 kb, 150 kb for 5S-rDNA in C. comosum, grossly in correspondence to their respective physical sizes at metaphase. (+info)
Cytomixis impairs meiosis and influences reproductive success in Chlorophytum comosum (Thunb) Jacq. - an additional strategy and possible implications.
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Spontaneous intercellular chromatin migration/cytomixis was observed to occur in the pollen mother cells (PMCs) of the Chlorophytum comosum for the first time. The migration through cytomictic channels was more pronounced in meiosis-I and very rare in meiosis-II. The process was associated with erratic meiosis, which was characterized by defects in chromosome organization and segregation. Cytomixis was more intense in the month of April than in July and consequently the frequency of meiotic irregularities was much more pronounced during the month of April. As a consequence of abnormal meiosis, fertility was drastically reduced resulting in meager seed efficiency of 17% only. Recombination system also does not guarantee the release of sufficient variability. We view the phenomenon of cytomixis as genetically controlled mechanism involving meiotic genes and operating through signal transduction pathway triggered by the environmental stimuli. The evolutionary significance and tenable hypothesis in the backdrop of existing literature is also proposed. (+info)
Morphology and life cycle of a new species of Didymium (Myxomycetes) from arid areas of Mexico.
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A new species of myxomycete, Didymium umbilicatum, isolated from the bark of Agavaceae, is described from arid zones of Mexico. This species was obtained from moist chamber cultures of Yucca spp. bark, collected in four different years from two states (Puebla and Queretaro) in central Mexico and found in the field from Hidalgo, Oaxaca and Puebla on the dead remains of Agave sp. The new species has small, flat, white sporocarps or short plasmodiocarps, 0.2-1.3 mm diam, and 0.15-0.4 mm tall. They are sessile on a reduced base or have a short, calcareous pale stalk and warted spores, warts fused in an irregular subreticulum by SEM. It is the sixth species of Didymium recently described from arid areas. The stability of the taxonomic characters of the species was confirmed by spore-to-spore culture on agar. Life cycle events are described from germination to sporulation. The morphology of the myxomycete specimens was examined with scanning electron microscopy and light microscopy, and micrographs of relevant details are included. (+info)
Elucidating the selenium and arsenic metabolic pathways following exposure to the non-hyperaccumulating Chlorophytum comosum, spider plant.
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Steroidal glycosides from Furcraea foetida and their cytotoxic activity.
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Two new spirostanol glycosides (1, 2) and a new furostanol glycoside (3), together with nine known steroidal glycosides (4-12) were isolated from the leaves of Furcraea foetida (Agavaceae). The structures of the new compounds were determined by spectroscopic analysis and the results of hydrolytic cleavage. The isolated compounds were evaluated for their cytotoxic activities against HL-60 human leukemia cells, A549 human lung adenocarcinoma cells, HSC-2 human oral squamous carcinoma cells, and HSC-4 human oral squamous carcinoma cells. (+info)
Evaluation of traditional medicines I: identification of PHELA using different chromatographic techniques.
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PHELA is a herbal mixture of four African traditional medicinal plants that has been used for decades in wasting conditions and is now being developed by the Medical Research Council (MRC) as an immune booster for patients with compromised immune system. A chromatographic fingerprint of PHELA was needed for quality control purposes. Here, a comprehensive method for fingerprinting of PHELA using different chromatographic techniques is described. It involved extraction of the PHELA by either acidic or a simple 'salting-out' method, followed by Thin Layer Chromatography (TLC) analysis and/or preparative Column Chromatography (CC). The products were thereafter analyzed by High Performance Liquid Chromatography with UV-detector (HPLC-UV), HPLC with fluorescence-detector (HPLC-FL) and Gas-Chromatography with a Mass Selective Detector spectrometer (GC-MSD). The fingerprints were successfully used to differentiate PHELA from another common herbal product made from Hypericum perforatum (St. John's Wort), thereby illustrating its high potential for use in fingerprinting of PHELA and in differentiating it from other herbal medicines. By validating the different chromatographic techniques on the standardized extraction methods, this approach will enable wide application in quality control of PHELA using acceptable procedures, thereby promoting effective monitoring of the finished product in all countries where it will be used. (+info)
Evaluation of traditional medicines III: the mechanism of immune modulation by PHELA.
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PHELA is a herbal traditional medicine that is under development for use as an immune booster in immune compromised individuals. Therefore, the aim of this study was to determine PHELA's mechanism of action by observing for changes in cytokine profiles. Four groups of Sprague Dawley rats (n = 8) were treated daily and separately with normal-saline, cyclosporine-A, PHELA-only and PHELA+ cyclosporine-A. Thereafter, 4 animals from each group were sacrificed after 7 and 14 days of treatment. Serum Th1 cytokines (IL-2, IFN-gamma and TNF-alpha) and Th2 cytokines (IL-4 and IL-10) were measured by ELISA. The concentrations of Th1 cytokines in the PHELA-only treated group were similar to the control group on days 7 and 14. However, the Th1 cytokines were higher in the PHELA+cyclosporine-A treated group compared to cyclosporine-A group, and cyclosporine-A concentrations were similar in both groups. These results show that PHELA did not stimulate Th1 cytokines of a normal immune system but stimulated them when the immune system was suppressed by cyclosporine-A. In conclusion, PHELA is an immune-stimulant to a compromised immune system. (+info)