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oai:www.ideals.illinois.edu:2142/19644 2023-07-10 col_2142_5131 col_2142_16357 com_2142_5130 com_2142_16356 com_2142_8913 com_2142_8903

2011-05-07T12:13:57Z Cheeseman, John M. Wickens, Linda Karolyn 2011-05-07T12:13:57Z 10000-01-01 1991 Plants vary in their whole plant strategies for managing the sodium (Na$\sp{+}$) present in their environment, but current models predict that they have a common strategy at the cellular level: exclusion from the cytoplasm. This entails either passive exclusion mediated by low plasma membrane permeability or active exclusion of passively acquired Na$\sp{+}$ which has moved down its electrochemical gradient into the cell. Whole plant studies using the halophyte Spergularia marina have demonstrated high permeability for Na$\sp{+}$ into and out of root cells and the research reported here investigates these mechanisms by directly measuring Na$\sp{+}$ transport using radiolabelled Na$\sp{+}$ and sealed plasma membrane vesicles from the roots of this species. This is the first report to characterize $\sp{22}$Na$\sp{+}$ transport using plant plasma membrane vesicles. Fractions from discontinuous and linear gradients of sucrose that were enriched in plasma membrane vesicles were identified for use in the $\sp{22}$Na$\sp{+}$ transport studies by the orthovanadate-sensitive P-type H$\sp{+}$-ATPase activity associated with them. Both the scalar and vectoral components of the activity were found to have negligible Na$\sp{+}$-dependent modifications. Indirect Na$\sp{+}$-dependent effects were observed, suggesting that Na$\sp{+}$ could disrupt K$\sp{+}$-dependent modifications of both components of the ATPase activity. An alternative explanation of the data was that an ATP-dependent, orthovanadate-insensitive, Na$\sp{+}$-dependent transport mechanism(s) mediated vesicle acidification. Radiolabelled Na$\sp{+}$ transport studies using similar conditions failed to show the presence of ATP-dependent transport of Na$\sp{+}$; and in addition, vesicle acidification studies, as well as $\sp{22}$Na$\sp{+}$ transport studies, suggested that a Na$\sp{+}$/H$\sp{+}$ antiport mechanism was not present in the plasma membrane. Two $\Delta\mu\sb{\rm Na+}$-driven transport mechanisms were identified using efflux studies. Lineweaver-Burk analysis predicted the presence of a Na$\sp{+}$ transport mechanism with a K$\sb{\rm m}$ of 93 mM Na$\sp{+}$ and a V$\sb{\rm max}$ of 52.6 nmoles Na$\sp{+}$ $\cdot$ (mg prot $\cdot$ min)$\sp{-1}$. Studies with monensin suggested that there was a Na$\sp{+}$-dependent alkalinization of the vesicles when the $\Delta\mu\sb{\rm Na+}$ was high. Made available in DSpace on 2011-05-07T12:13:57Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9211033.pdf: 5971142 bytes, checksum: 2efa9ed1cab76af1ffe0c37b9b7a2c67 (MD5) Previous issue date: 1991 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:38:27Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:16:02-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9211033 (UMI)AAI9211033 http://hdl.handle.net/2142/19644 eng Copyright 1991 Wickens, Linda Karolyn Biology, Botany Biology, Cell Biology, Plant Physiology Characterization of sodium transport at the plasma membrane of Spergularia marina text Plant Biology Biology, Botany University of Illinois at Urbana-Champaign Dissertation Ph.D.