The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Jason D. Berndt - One of the best experts on this subject based on the ideXlab platform.
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DOG1 Controls Seed Germination
Science Signaling, 2014Co-Authors: Jason D. BerndtAbstract:Variation in seed dormancy enables plants to adapt to different climates. Mature seeds of most angiosperms have a dry outer coating called the testa and an endosperm, including the embryonic growth zone known as the Radicle-lower hypocotyl axis and an overlying cap. During germination, the testa and endosperm cap rupture, enabling the first Root (Radicle) to emerge. DOG1 (DELAY OF GERMINATION 1) is a protein that accumulates in a temperature-dependent manner during seed maturation. Seeds from Arabidopsis thaliana with deletion of DOG1 do not have a dormant phase but take longer to germinate. Graeber et al . found that Lepidium sativum , which is in the same family (Brassicaceae) as A. thaliana but naturally does not have seed dormancy, contained homologs of DOG1 that were expressed in seeds. Transgenic expression of A. thaliana DOG1 ( AtDOG1 ) in L. sativum markedly delayed testa and endosperm rupture and seed germination and increased the endosperm cap’s resistance to mechanical puncture. Manipulations that weaken the endosperm cap, including exposure to the plant hormone gibberillic acid (GA), accelerated germination of seeds from L. sativum expressing AtDOG1 . Likewise, reducing the temperature from 24o to 18oC during imbibition (wetting) reduced the endosperm cap’s resistance to puncture and accelerated germination of seeds from these plants. Expression of AtDOG1 in L. sativum altered temperature-dependent changes in the expression of genes encoding proteins associated with cap weakening and GA metabolism and the relative abundances of several GA metabolites. In A. thaliana , wild-type seeds and those lacking DOG1 had differences in the temperature-dependent regulation of germination. Expression of LesaDOG1A in the AtDOG1 -deficient seeds did not restore wild-type germination properties but rather enabled increased germination of seeds imbibed at the lower temperature. Thus, AtDOG1 may influence seed dormancy, at least in part, by repressing GA-mediated weakening of the endosperm cap. K. Graeber, A. Linkies, T. Steinbrecher, K. Mummenhoff, D. Tarkowska, V. Tureckova, M. Ignatz, K. Sperber, A. Voegele, H. de Jong, T. Urbanova, M. Strnad, G. Leubner-Metzger, DELAY OF GERMINATION 1 mediates a conserved coat-dormancy mechanism for the temperature- and gibberellin-dependent control of seed germination. Proc. Natl. Acad. Sci. U.S.A. 111 , E3571–E3580 (2014). [Abstract][Full Text]
Albertus H. De Boer - One of the best experts on this subject based on the ideXlab platform.
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Abscisic acid and 14‐3‐3 proteins control K+ channel activity in barley embryonic Root
The Plant journal : for cell and molecular biology, 2004Co-Authors: Paul W.j. Van Den Wijngaard, Mark P. Sinnige, Ilja Roobeek, Annet Reumer, Peter J. Schoonheim, Jos Mol, Mei Wang, Albertus H. De BoerAbstract:Germination of seeds proceeds in general in two phases, an initial imbibition phase and a subsequent growth phase. In grasses like barley, the latter phase is evident as the emergence of the embryonic Root (Radicle). The hormone abscisic acid (ABA) inhibits germination because it prevents the embryo from entering and completing the growth phase. Genetic and physiological studies have identified many steps in the ABA signal transduction cascade, but how it prevents Radicle elongation is still not clear. For elongation growth to proceed, uptake of osmotically active substances (mainly K(+)) is essential. Therefore, we have addressed the question of how the activity of K(+) permeable ion channels in the plasma membrane of Radicle cells is regulated under conditions of slow (+ABA) and rapid germination (+fusicoccin). We found that ABA arrests Radicle growth, inhibits net K(+) uptake and reduces the activity of K(+) (in) channels as measured with the patch-clamp technique. In contrast, fusicoccin (FC), a well-known stimulator of germination, stimulates Radicle growth, net K(+) uptake and reduces the activity of K(+) (out) channels. Both types of channels are under the control of 14-3-3 proteins, known as integral components of signal transduction pathways and instrumental in FC action. Intriguingly, 14-3-3 affected both channels in an opposite fashion: whereas K(+) (in) channel activity was fully dependent upon 14-3-3 proteins, K(+) (out) channel activity was reduced by 14-3-3 proteins by 60%. Together with previous data showing that 14-3-3 proteins control the activity of the plasma membrane H(+)-ATPase, this makes 14-3-3 a prime candidate for molecular master regulator of the cellular osmo-pump. Regulation of the osmo-pump activity by ABA and FC is an important mechanism in controlling the growth of the embryonic Root during seed germination.
JA Murray - One of the best experts on this subject based on the ideXlab platform.
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D-type cyclins activate division in the Root apex to promote seed germination in Arabidopsis.
Proc Natl Acad Sci U S A, 2005Co-Authors: JA MurrayAbstract:Seeds provide survival and dispersal capabilities by protecting the dormant mature plant embryo. Germination and resumption of development under favourable conditions requires the reinitiation of cell growth and division through poorly understood processes. Here we show that four phases of cell division activation during germination in Arabidopsis are related to external morphological changes. Cell division initiates in the Root apical meristem (RAM) before Root protrusion, followed by sequential activation of cell division in the cotyledons, shoot apical meristem (SAM), and secondary meristems. Major changes in transcript levels of >2,000 genes precede Root emergence, including expression peaks of six D-type (CYCD) and two A-type cyclins. Two further CYCDs are activated later with the SAM. Early activated CYCDs play key roles in regulating the extent of cell division, because loss-of-function alleles of early CYCDs display reduced division activation and consequential delayed Root emergence. Conversely, elevation of early CYCDs increases cell cycle activation in the RAM and promotes embryonic Root (Radicle) protrusion, whereas a later-acting CYCD does not. These phenotypes, together with their overlapping expression domains, support a cumulative action of a subset of CYCDs in cell cycle reactivation, rather than a complete functional redundancy. This analysis reveals a phenotype associated with loss-of-function of a plant cyclin and demonstrates that D-type cyclins regulate cell cycle reentry during meristem activation to promote successful germination and early seedling growth.
Gerhard Leubner-metzger - One of the best experts on this subject based on the ideXlab platform.
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Coleorhiza-enforced seed dormancy: a novel mechanism to control germination in grasses.
The New phytologist, 2020Co-Authors: Thomas Holloway, Tina Steinbrecher, Marta Pérez, Anne Seville, David Stock, Kazumi Nakabayashi, Gerhard Leubner-metzgerAbstract:How the biophysical properties of overlaying tissues control growth, such as the embryonic Root (Radicle) during seed germination, is a fundamental question. In eudicot seeds the endosperm surrounding the Radicle confers coat dormancy and controls germination responses through modulation of its cell wall mechanical properties. Far less is known for grass caryopses that differ in tissue morphology. Here we report that the coleorhiza, a sheath-like organ that surrounds the Radicle in grass embryos, performs the same role in the grass weed Avena fatua (common wild oat). We combined innovative biomechanical techniques, tissue ablation, microscopy, tissue-specific gene and enzyme activity expression with the analysis of hormones and oligosaccharides. The combined experimental work demonstrates that in grass caryopses the coleorhiza indeed controls germination for which we provide direct biomechanical evidence. We show that the coleorhiza becomes reinforced during dormancy maintenance and weakened during germination. Xyloglucan endotransglycosylases/hydrolases may have a role in coleorhiza reinforcement through cell wall remodelling to confer coat dormancy. The control of germination by coleorhiza-enforced dormancy in grasses is an example of the convergent evolution of mechanical restraint by overlaying tissues.
Adebayo Gbolade - One of the best experts on this subject based on the ideXlab platform.
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Growth inhibitory and cytotoxic study of Ceiba pentandra (L.) Gaertn. Leaf (Malvaceae) and Cascabela thevetia (L.) Lippold Root bark (Apocynaceae)
Journal of Pharmacognosy and Phytochemistry, 2019Co-Authors: Adebayo Gbolade, Onosetale Ojeh-oziegbe, Precious UazamaAbstract:Ceiba pentandra (L.) Gaertn. leaf (Malvaceae) and Cascabela thevetia (L.) Lippold (Apocynaceae) Root bark were investigated for growth inhibitory effect on guinea corn (Sorghum bicolor) seeds and cytotoxicity on tadpoles (Raniceps ranninus) in vitro. Methanol extract and solvent fractions of both plants at 0.25 – 5.0 mg/ml gave significant decreases in mean Radicle length of guinea corn seeds (anti-proliferative action) which was concentration-dependent. Growth inhibition of Root Radicle at the most effective concentration, 5 mg/ml, was not dependent on incubation period. Ceiba pentandra aqueous fraction gave remarkable growth inhibition (86%) at 24h while other tested agents were similar in activity (78-76%). At 48h, the performance was methanol extract > aqueous fraction = chloroform fraction > ethyl acetate fraction (89-69%). Cascabela pentandra gave reasonable maximum growth inhibition only at 24h: chloroform fraction = ethyl acetate (69%) and aqueous fraction = methanol extract (59%). Ceiba pentandra (LC50 4.8-6.0 mg/ml) proved to be more cytotoxic on tadpoles than Cascabela thevetia (LC50 5.3-6.4 mg/ml) within 24h. Cytotoxicity ranking with Ceiba pentandra was ethyl acetate fraction > methanol extract > chloroform fraction > aqueous fraction, while Cascabela thevetia gave ethyl acetate fraction > aqueous fraction > methanol extract. Data reported herein showed that Ceiba pentandra was the more potent cytotoxic and growth inhibitory plant. These findings hereby justify the folkloric purpose of Ceiba pentandra and Cascabela thevetia in the treatment of oxidative stress-induced diseases.
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Anti-proliferative and cytotoxic properties of Spondias mombin L. ( Anacardiaceae ) stem bark
Journal of Pharmaceutical and Allied Sciences, 2019Co-Authors: Adebayo Gbolade, D.n. Edom, J.t. Ogunleye, S.t. MuhammadAbstract:An investigation was conducted into the anti-proliferative effect on guinea corn (Sorghum bicolor) Root Radicle and cytotoxicity on tadpoles (Raniceps ranninus) of methanol extract and solvent fractions of Spondias mombin L. (Anacardiaceae) stem bark reputed in African traditional medicine for various purposes including treatment of tumours. The methanol extract and solvent fractions at 0.25 – 5.0 mg/ml gave significant decreases in mean Radicle length of guinea corn Root Radicle (anti-proliferative effect) which was concentration-dependent. Only the chloroform (61.5-83.3%) and ethyl acetate (65.7-71.7%) fractions, showed promising growth inhibitory effects on Root Radicle at the highest concentration of 5 mg/ml. On tadpole cytotoxicity, chloroform fraction, tested at the highest concentration of 20 mg/ml, resulted in complete tadpole mortality equivalent to that of the positive control, chloramphenicol tested at 0.5 mg/ml. S. mombin (chloroform fraction > aqueous fraction > ethyl acetate fraction, LC50 5.1 – 8.5 mg/ml) showed promising antitumour potential. Data reported herein indicate that S. mombin is a potent cytotoxic and anti-proliferative plant and corroborate the folkloric use of the plant in the treatment of tumour-related diseases. Key words: Spondias mombin, anti-proliferative activity, guinea corn seeds, cytotoxicity, tadpoles
