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William M. Gray - One of the best experts on this subject based on the ideXlab platform.
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Rapid Auxin-Mediated Cell Expansion.
Annual review of plant biology, 2020Co-Authors: Edgar P. Spalding, William M. GrayAbstract:The promotive effect of auxin on shoot Cell Expansion provided the bioassay used to isolate this central plant hormone nearly a century ago. While the mechanisms underlying auxin perception and signaling to regulate transcription have largely been elucidated, how auxin controls Cell Expansion is only now attaining molecular-level definition. The good news is that the decades-old acid growth theory invoking plasma membrane H+-ATPase activation is still useful. The better news is that a mechanistic framework has emerged, wherein Small Auxin Up RNA (SAUR) proteins regulate protein phosphatases to control H+-ATPase activity. In this review, we focus on rapid auxin effects, their relationship to H+-ATPase activation and other transporters, and dependence on TIR1/AFB signaling. We also discuss how some observations, such as near-instantaneous effects on ion transport and root growth, do not fit into a single, comprehensive explanation of how auxin controls Cell Expansion, and where more research is warranted.
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A subset of plasma membrane-localized PP2C.D phosphatases negatively regulate SAUR-mediated Cell Expansion in Arabidopsis.
PLoS genetics, 2018Co-Authors: Hong Ren, Angela K. Spartz, Mee Yeon Park, Jeh Haur Wong, William M. GrayAbstract:The plant hormone auxin regulates numerous growth and developmental processes throughout the plant life cycle. One major function of auxin in plant growth and development is the regulation of Cell Expansion. Our previous studies have shown that SMALL AUXIN UP RNA (SAUR) proteins promote auxin-induced Cell Expansion via an acid growth mechanism. These proteins inhibit the PP2C.D family phosphatases to activate plasma membrane (PM) H+-ATPases and thereby promote Cell Expansion. However, the functions of individual PP2C.D phosphatases are poorly understood. Here, we investigated PP2C.D-mediated control of Cell Expansion and other aspects of plant growth and development. The nine PP2C.D family members exhibit distinct subCellular localization patterns. Our genetic findings demonstrate that the three plasma membrane-localized members, PP2C.D2, PP2C.D5, and PP2C.D6, are the major regulators of Cell Expansion. These phosphatases physically interact with SAUR19 and PM H+-ATPases, and inhibit Cell Expansion by dephosphorylating the penultimate threonine of PM H+-ATPases. PP2C.D genes are broadly expressed and are crucial for diverse plant growth and developmental processes, including apical hook development, phototropism, and organ growth. GFP-SAUR19 overexpression suppresses the growth defects conferred by PP2C.D5 overexpression, indicating that SAUR proteins antagonize the growth inhibition conferred by the plasma membrane-localized PP2C.D phosphatases. Auxin and high temperature upregulate the expression of some PP2C.D family members, which may provide an additional layer of regulation to prevent plant overgrowth. Our findings provide novel insights into auxin-induced Cell Expansion, and provide crucial loss-of-function genetic support for SAUR-PP2C.D regulatory modules controlling key aspects of plant growth.
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saur inhibition of pp2c d phosphatases activates plasma membrane h atpases to promote Cell Expansion in arabidopsis
The Plant Cell, 2014Co-Authors: Angela K. Spartz, Michael R Sussman, Sang H. Lee, Angus S. Murphy, Hong Ren, Mee Yeon Park, Kristin N Grandt, Paul Overvoorde, William M. GrayAbstract:The plant hormone auxin promotes Cell Expansion. Forty years ago, the acid growth theory was proposed, whereby auxin promotes proton efflux to acidify the apoplast and facilitate the uptake of solutes and water to drive plant Cell Expansion. However, the underlying molecular and genetic bases of this process remain unclear. We have previously shown that the SAUR19-24 subfamily of auxin-induced SMALL AUXIN UP-RNA (SAUR) genes promotes Cell Expansion. Here, we demonstrate that SAUR proteins provide a mechanistic link between auxin and plasma membrane H+-ATPases (PM H+-ATPases) in Arabidopsis thaliana. Plants overexpressing stabilized SAUR19 fusion proteins exhibit increased PM H+-ATPase activity, and the increased growth phenotypes conferred by SAUR19 overexpression are dependent upon normal PM H+-ATPase function. We find that SAUR19 stimulates PM H+-ATPase activity by promoting phosphorylation of the C-terminal autoinhibitory domain. Additionally, we identify a regulatory mechanism by which SAUR19 modulates PM H+-ATPase phosphorylation status. SAUR19 as well as additional SAUR proteins interact with the PP2C-D subfamily of type 2C protein phosphatases. We demonstrate that these phosphatases are inhibited upon SAUR binding, act antagonistically to SAURs in vivo, can physically interact with PM H+-ATPases, and negatively regulate PM H+-ATPase activity. Our findings provide a molecular framework for elucidating auxin-mediated control of plant Cell Expansion.
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The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion
The Plant journal : for cell and molecular biology, 2012Co-Authors: Angela K. Spartz, Sang H. Lee, Jonathan P. Wenger, Nathalie Gonzalez, Hironori Itoh, Dirk Inze, Wendy A. Peer, Angus S. Murphy, Paul J. Overvoorde, William M. GrayAbstract:Summary The plant hormone auxin controls numerous aspects of plant growth and development by regulating the expression of hundreds of genes. SMALL AUXIN UP RNA (SAUR) genes comprise the largest family of auxin-responsive genes, but their function is unknown. Although prior studies have correlated the expression of some SAUR genes with auxin-mediated Cell Expansion, genetic evidence implicating SAURs in Cell Expansion has not been reported. The Arabidopsis SAUR19, SAUR20, SAUR21, SAUR22, SAUR23, and SAUR24 (SAUR19–24) genes encode a subgroup of closely related SAUR proteins. We demonstrate that these SAUR proteins are highly unstable in Arabidopsis. However, the addition of an N-terminal GFP or epitope tag dramatically increases the stability of SAUR proteins. Expression of these stabilized SAUR fusion proteins in Arabidopsis confers numerous auxin-related phenotypes indicative of increased and/or unregulated Cell Expansion, including increased hypocotyl and leaf size, defective apical hook maintenance, and altered tropic responses. Furthermore, seedlings expressing an artificial microRNA targeting multiple members of the SAUR19–24 subfamily exhibit short hypocotyls and reduced leaf size. Together, these findings demonstrate that SAUR19–24 function as positive effectors of Cell Expansion. This regulation may be achieved through the modulation of auxin transport, as SAUR gain-of-function and loss-of-function seedlings exhibit increased and reduced basipetal indole-3-acetic acid transport, respectively. Consistent with this possibility, SAUR19–24 proteins predominantly localize to the plasma membrane.
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The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion
Plant Journal, 2012Co-Authors: Angela K. Spartz, Sang H. Lee, Jonathan P. Wenger, Nathalie Gonzalez, Hironori Itoh, Dirk Inze, Wendy A. Peer, Angus S. Murphy, Paul J. Overvoorde, William M. GrayAbstract:The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion. The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion
Alison W. Roberts - One of the best experts on this subject based on the ideXlab platform.
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Tracheary element differentiation is correlated with inhibition of Cell Expansion in xylogenic mesophyll suspension cultures
Plant Physiology and Biochemistry, 2004Co-Authors: Alison W. RobertsAbstract:Abstract To test the hypothesis that xylogenesis is coupled to Cell growth suppression, Cell Expansion in Zinnia elegans L. var. Envy mesophyll suspension cultures was manipulated by varying the extraCellular osmolarity and the effect on xylogenesis was examined. Cell Expansion and tracheary element differentiation were inversely related along a gradient of extraCellular osmolarity ranging from 200 to 400 mOsm, supporting the hypothesis that tracheary element differentiation is coupled to cessation of Cell Expansion. Above 300 mOsm, reduction in the number of Cells that differentiated into tracheary elements coincided with an increase in the number of plasmolyzed Cells as extraCellular osmolarity was increased, indicating that plasmolysis inhibits tracheary element differentiation, although not specifically. Using the plasmolysis method we showed that Cellular osmolarity within populations of isolated Zinnia mesophyll Cells ranges from 250 to 600 mOsm with a mean of 425 mOsm. The broad range in Cellular osmolarity within Zinnia mesophyll Cell populations, coupled with inhibition of differentiation in the low range due to Cell Expansion and in the high range due to plasmolysis, may help explain why tracheary element differentiation in Zinnia suspension cultures is never complete nor perfectly synchronous and enable further optimization of this culture system.
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A Secreted Factor Inducs Cell Expansion and Formation of Metaxylem-Like Tracheary Elements in Xylogenic Suspension Cultures of Zinnia
Plant physiology, 1997Co-Authors: Alison W. Roberts, S. G. Donovan, C. H. HaiglerAbstract:Conditioned medium from mesophyll Cell-suspension cultures of Zinnia elegans L. has striking effects on Cell Expansion and tracheary element differentiation when applied to cultures of freshly isolated mesophyll Cells. These effects include (a) induction of early Cell Expansion, (b) delay in differentiation by 48 h or more, (c) reduction in the synchrony of differentiation, and (d) early formation of very large, metaxylem-like tracheary elements. Like reduced osmotic potential and buffering at pH 5.5, conditioned medium appears to have its primary effect on Cell Expansion. Partial characterization of the Expansion-inducing factor indicates that it is heat stable, of low molecular mass, and is resistant to protease. It also binds reversibly to concanavalin A but is not adsorbed by charcoal. We suggest that the secreted factor may be an oligosaccharide involved in the coordination of Cell Expansion and differentiation and the regulation of the protoxylem-like to metaxylem-like transition in xylogenic suspension cultures.
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Cell Expansion and Tracheary Element Differentiation Are Regulated by ExtraCellular pH in Mesophyll Cultures of Zinnia elegans L
Plant physiology, 1994Co-Authors: Alison W. Roberts, Candace H. HaiglerAbstract:The effects of medium pH on Cell Expansion and tracheary element (TE) differentiation were investigated in differentiating mesophyll suspension cultures of Zinnia elegans L. In unbuffered cultures initially adjusted to pH 5.5, the medium pH fluctuated reproducibly, decreasing about 1 unit prior to the onset of TE differentiation and then increasing when the initiation of new Tes was complete. Elimination of large pH fluctuations by buffering the culture medium with 20 mM 2-(N-morpholino)ethanesulfonic acid altered both Cell Expansion and TE differentiation, whereas altering the starting pH of unbuffered culture medium had no effect on either process. Cell Expansion in buffered cultures was pH dependent with an optimum of 5.5 to 6.0. The direction of Cell Expansion was also pH dependent in buffered cultures. Cells elongated at pH 5.5 to 6.0, whereas isodiametric Cell Expansion was predominant at pH 6.5 to 7.0. The onset of TE differentiation was delayed when the pH was buffered higher or lower than 5.0. However, TEs eventually appeared in cultures buffered at pH 6.5 to 7.0, indicating that a decrease in pH to 5.0 is not necessary for differentiation. Very large TEs with secondary Cell wall thickenings resembling metaxylem differentiated in cultures buffered at pH 5.5 to 6.0, which also showed the greatest Cell Expansion. The correlation between Cell Expansion and delayed differentiation of large, metaxylem-like TEs may indicate a link between the regulatory mechanisms controlling Cell Expansion and TE differentiation.
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PALISADE MESOPHYLL Cell Expansion DURING LEAF DEVELOPMENT IN ZINNIA ELEGANS (ASTERACEAE)
American Journal of Botany, 1994Co-Authors: Benjamin W. Knight, Alison W. RobertsAbstract:which Cells in various stages of Expansion could be selectively isolated for culture, and 2) develop a basis for comparison of rate and extent of mesophyll Cell Expansion in culture with that in the leaf. Palisade mesophyll Cells were isolated from expanding leaves by gentle physical maceration without the use of enzymes. Isolated Cells from leaves in different stages of Expansion were then measured by computer image analysis. Analysis of size frequency distributions showed that unexpanded Cells can be isolated from the entire blade of small leaves or the basal regions of partially expanded leaves. Fully expanded Cells can be obtained from the apical and middle regions of partially expanded leaves. Within the leaf, Zinnia mesophyll Cells expanded from about 400 ,Am2 to about 2,300 ,Am2 at an estimated rate of 160 ,Am2 d-'. The percent increase in Cell length exceeded the percent increase in Cell width. Expansion of mesophyll Cells continued for 6-8 d after epidermal Expansion ceased. This difference in the timing of Cell Expansion in epidermal and mesophyll Cells indicates that different regulatory factors may be operating in these adjacent tissues and underscores the importance of investigating the regulation of mesophyll Cell Expansion at the Cellular level. The palisade mesophyll is the primary photosynthetic tissue of most dicotyledonous plants. The structure of this tissue is specialized for optimal light absorption and gas exchange and exhibits considerable developmental plasticity in response to light, temperature, water stress, and salt stress (Nobel and Walker, 1985). Despite evidence that palisade mesophyll structure influences primary productivity (Nobel, 1976; Sims and Pearcy, 1992), little is known about the Cellular mechanisms that control the extent and direction of palisade mesophyll Cell Expansion, processes that are essential in the development of an efficiently functioning tissue. This gap in our knowledge is in part due to technical difficulties. It has been possible to study the dynamic aspects of leaf epidermal Cell Expansion by direct mea
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Cell Expansion and Tracheary Element Differentiation Are Regulated by ExtraCellular pH in Mesophyll Cultures of
1994Co-Authors: Alison W. Roberts, Candace H. HaiglerAbstract:The effeds of medium pH on Cell Expansion and tracheary element (TE) differentiation were investigated in differentiating mesophyll suspension cultures of Zinnia elegans 1. In unbuffered cultures initially adjusted to pH 5.5, the medium pH fluduated reproducibly, decreasing about 1 unit prior to the onset of TE differentiation and then increasing when the initiation of new TEs was complete. Elimination of large pH fluctuations by buffering acid altered both Cell Expansion and TE differentiation, whereas altering the starting pH of unbuffered culture medium had no effed on either process. Cell Expansion in buffered cultures was pH dependent with an optimum of 5.5 to 6.0. The direction of Cell Expansion was also pH dependent in buffered cultures. Cells elongated at pH 5.5 to 6.0, whereas isodiametric Cell Expansion was predominant at pH 6.5 to 7.0. The onset of TE differentiation was delayed when the pH was buffered higher or lower than 5.0. However, TEs eventually appeared in cultures buffered at pH 6.5 to 7.0, indicating that a decrease in pH to 5.0 is not necessary for differentiation. Very large TEs with secondary Cell wall thickenings resembling metaxylem differentiated in cultures buffered at pH 5.5 to 6.0, which also showed the greatest Cell Expansion. The correlation between Cell Expansion and delayed differentiation of large, metaxylem-like TEs may indicate a link between the regulatory mechanisms controlling Cell Expansion and TE differentiation. the culture medium with 20 m,+q 2-(N-morpholino)ethanesulfonic proliferation was promoted at pH 5.4t whereas shoot
Angela K. Spartz - One of the best experts on this subject based on the ideXlab platform.
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A subset of plasma membrane-localized PP2C.D phosphatases negatively regulate SAUR-mediated Cell Expansion in Arabidopsis.
PLoS genetics, 2018Co-Authors: Hong Ren, Angela K. Spartz, Mee Yeon Park, Jeh Haur Wong, William M. GrayAbstract:The plant hormone auxin regulates numerous growth and developmental processes throughout the plant life cycle. One major function of auxin in plant growth and development is the regulation of Cell Expansion. Our previous studies have shown that SMALL AUXIN UP RNA (SAUR) proteins promote auxin-induced Cell Expansion via an acid growth mechanism. These proteins inhibit the PP2C.D family phosphatases to activate plasma membrane (PM) H+-ATPases and thereby promote Cell Expansion. However, the functions of individual PP2C.D phosphatases are poorly understood. Here, we investigated PP2C.D-mediated control of Cell Expansion and other aspects of plant growth and development. The nine PP2C.D family members exhibit distinct subCellular localization patterns. Our genetic findings demonstrate that the three plasma membrane-localized members, PP2C.D2, PP2C.D5, and PP2C.D6, are the major regulators of Cell Expansion. These phosphatases physically interact with SAUR19 and PM H+-ATPases, and inhibit Cell Expansion by dephosphorylating the penultimate threonine of PM H+-ATPases. PP2C.D genes are broadly expressed and are crucial for diverse plant growth and developmental processes, including apical hook development, phototropism, and organ growth. GFP-SAUR19 overexpression suppresses the growth defects conferred by PP2C.D5 overexpression, indicating that SAUR proteins antagonize the growth inhibition conferred by the plasma membrane-localized PP2C.D phosphatases. Auxin and high temperature upregulate the expression of some PP2C.D family members, which may provide an additional layer of regulation to prevent plant overgrowth. Our findings provide novel insights into auxin-induced Cell Expansion, and provide crucial loss-of-function genetic support for SAUR-PP2C.D regulatory modules controlling key aspects of plant growth.
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saur inhibition of pp2c d phosphatases activates plasma membrane h atpases to promote Cell Expansion in arabidopsis
The Plant Cell, 2014Co-Authors: Angela K. Spartz, Michael R Sussman, Sang H. Lee, Angus S. Murphy, Hong Ren, Mee Yeon Park, Kristin N Grandt, Paul Overvoorde, William M. GrayAbstract:The plant hormone auxin promotes Cell Expansion. Forty years ago, the acid growth theory was proposed, whereby auxin promotes proton efflux to acidify the apoplast and facilitate the uptake of solutes and water to drive plant Cell Expansion. However, the underlying molecular and genetic bases of this process remain unclear. We have previously shown that the SAUR19-24 subfamily of auxin-induced SMALL AUXIN UP-RNA (SAUR) genes promotes Cell Expansion. Here, we demonstrate that SAUR proteins provide a mechanistic link between auxin and plasma membrane H+-ATPases (PM H+-ATPases) in Arabidopsis thaliana. Plants overexpressing stabilized SAUR19 fusion proteins exhibit increased PM H+-ATPase activity, and the increased growth phenotypes conferred by SAUR19 overexpression are dependent upon normal PM H+-ATPase function. We find that SAUR19 stimulates PM H+-ATPase activity by promoting phosphorylation of the C-terminal autoinhibitory domain. Additionally, we identify a regulatory mechanism by which SAUR19 modulates PM H+-ATPase phosphorylation status. SAUR19 as well as additional SAUR proteins interact with the PP2C-D subfamily of type 2C protein phosphatases. We demonstrate that these phosphatases are inhibited upon SAUR binding, act antagonistically to SAURs in vivo, can physically interact with PM H+-ATPases, and negatively regulate PM H+-ATPase activity. Our findings provide a molecular framework for elucidating auxin-mediated control of plant Cell Expansion.
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The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion
The Plant journal : for cell and molecular biology, 2012Co-Authors: Angela K. Spartz, Sang H. Lee, Jonathan P. Wenger, Nathalie Gonzalez, Hironori Itoh, Dirk Inze, Wendy A. Peer, Angus S. Murphy, Paul J. Overvoorde, William M. GrayAbstract:Summary The plant hormone auxin controls numerous aspects of plant growth and development by regulating the expression of hundreds of genes. SMALL AUXIN UP RNA (SAUR) genes comprise the largest family of auxin-responsive genes, but their function is unknown. Although prior studies have correlated the expression of some SAUR genes with auxin-mediated Cell Expansion, genetic evidence implicating SAURs in Cell Expansion has not been reported. The Arabidopsis SAUR19, SAUR20, SAUR21, SAUR22, SAUR23, and SAUR24 (SAUR19–24) genes encode a subgroup of closely related SAUR proteins. We demonstrate that these SAUR proteins are highly unstable in Arabidopsis. However, the addition of an N-terminal GFP or epitope tag dramatically increases the stability of SAUR proteins. Expression of these stabilized SAUR fusion proteins in Arabidopsis confers numerous auxin-related phenotypes indicative of increased and/or unregulated Cell Expansion, including increased hypocotyl and leaf size, defective apical hook maintenance, and altered tropic responses. Furthermore, seedlings expressing an artificial microRNA targeting multiple members of the SAUR19–24 subfamily exhibit short hypocotyls and reduced leaf size. Together, these findings demonstrate that SAUR19–24 function as positive effectors of Cell Expansion. This regulation may be achieved through the modulation of auxin transport, as SAUR gain-of-function and loss-of-function seedlings exhibit increased and reduced basipetal indole-3-acetic acid transport, respectively. Consistent with this possibility, SAUR19–24 proteins predominantly localize to the plasma membrane.
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The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion
Plant Journal, 2012Co-Authors: Angela K. Spartz, Sang H. Lee, Jonathan P. Wenger, Nathalie Gonzalez, Hironori Itoh, Dirk Inze, Wendy A. Peer, Angus S. Murphy, Paul J. Overvoorde, William M. GrayAbstract:The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion. The SAUR19 subfamily of SMALL AUXIN UP RNA genes promote Cell Expansion
C. H. Haigler - One of the best experts on this subject based on the ideXlab platform.
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A Secreted Factor Inducs Cell Expansion and Formation of Metaxylem-Like Tracheary Elements in Xylogenic Suspension Cultures of Zinnia
Plant physiology, 1997Co-Authors: Alison W. Roberts, S. G. Donovan, C. H. HaiglerAbstract:Conditioned medium from mesophyll Cell-suspension cultures of Zinnia elegans L. has striking effects on Cell Expansion and tracheary element differentiation when applied to cultures of freshly isolated mesophyll Cells. These effects include (a) induction of early Cell Expansion, (b) delay in differentiation by 48 h or more, (c) reduction in the synchrony of differentiation, and (d) early formation of very large, metaxylem-like tracheary elements. Like reduced osmotic potential and buffering at pH 5.5, conditioned medium appears to have its primary effect on Cell Expansion. Partial characterization of the Expansion-inducing factor indicates that it is heat stable, of low molecular mass, and is resistant to protease. It also binds reversibly to concanavalin A but is not adsorbed by charcoal. We suggest that the secreted factor may be an oligosaccharide involved in the coordination of Cell Expansion and differentiation and the regulation of the protoxylem-like to metaxylem-like transition in xylogenic suspension cultures.
Yung-luen Shih - One of the best experts on this subject based on the ideXlab platform.
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Induction of Cell Expansion of goldfish melanocytoma Cells (GMM‐1) by epinephrine and dexamethasone requires external calcium.
Cell Biology International, 1993Co-Authors: Yung-luen Shih, Szecheng J. LoAbstract:Treatment of GMM-1 (a goldfish melanocytoma Cell line) Cells with epinephrine induced a rapid Cell Expansion (flattening of Cells, extension and broadening of Cellular processes) similar to the effect of dexamethasone reported previously (Shih et al., 1990). Studies on the possible involvement of secondary messengers in Cell Expansion indicated that (i) both 8-bromo-CAMP and forskolin caused Cell shrinking (the opposite of Cell Expansion); (ii) TPA also caused Cell shrinking; (iii) phospholipid derivatives, such as 1,2-dioctanoyl-sn-glycerol, lysophosphatidic acid, and arachidonic acid caused Cell Expansion; and (iv) EGTA (calcium chelator) and nifedipine (calcium channel blocker) inhibited the effect of epinephrine. Together with the previous findings, these observations indicate that epinephrine and dexamethasone may share a common pathway in triggering an external calcium influx to cause Cell Expansion. The results of the effects of epinephrine agonists and antagonists, together with those of other workers, also show that there are multiple isoforms of adrenoceptor in the goldfish.
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Induction of Cell Expansion of goldfish melanocytoma Cells (GMM-1) by epinephrine and dexamethasone requires external calcium.
Cell biology international, 1993Co-Authors: Yung-luen ShihAbstract:Treatment of GMM-1 (a goldfish melanocytoma Cell line) Cells with epinephrine induced a rapid Cell Expansion (flattening of Cells, extension and broadening of Cellular processes) similar to the effect of dexamethasone reported previously (Shih et al., 1990). Studies on the possible involvement of secondary messengers in Cell Expansion indicated that (i) both 8-bromo-CAMP and forskolin caused Cell shrinking (the opposite of Cell Expansion); (ii) TPA also caused Cell shrinking; (iii) phospholipid derivatives, such as 1,2-dioctanoyl-sn-glycerol, lysophosphatidic acid, and arachidonic acid caused Cell Expansion; and (iv) EGTA (calcium chelator) and nifedipine (calcium channel blocker) inhibited the effect of epinephrine. Together with the previous findings, these observations indicate that epinephrine and dexamethasone may share a common pathway in triggering an external calcium influx to cause Cell Expansion. The results of the effects of epinephrine agonists and antagonists, together with those of other workers, also show that there are multiple isoforms of adrenoceptor in the goldfish.