Salt stress upregulates periplasmic arabinogalactan proteins: using salt stress to analyse AGP function.
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| Abstract |
Arabinogalactan proteins (AGPs) are implicated in cell expansion by unknown mechanisms, thus AGP content and cell-expansion rate might be correlated. We used Yariv reagent to quantify release rates and distribution of AGP at the cell surface of tobacco BY-2 cells: plasma membrane (M); soluble periplasmic AGPs released by cell rupture (S); cell wall (W); and growth medium (Gsink). In contrast to earlier reports, we observed massive upregulation of AGPs in salt-stressed cells, and hence the absence of a simple, direct cause-and-effect relationship between growth rate and AGP release. There was a more subtle connection. A dynamic flux model, M-->S-->W-->Gsink, indicated that turnover was nondegradative, with little free diffusion of AGPs trapped in the pectic matrix of nonadapted cells where transmural migration of high molecular-weight AGPs occurred mainly by plug flow (apposition and extrusion). In contrast, however, an up to sixfold increased AGP release rate in the slower-growing salt-adapted cells indicated a greatly increased rate of AGP diffusion through a much more highly porous pectic network. We hypothesize that classical AGPs act as pectin plasticizers. This explains how beta-D-glycosyl Yariv reagents might inhibit expansion growth by crosslinking monomeric AGPs, and thus mimic an AGP loss-of-function mutation.
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| Authors | Derek T A Lamport, Marcia J Kieliszewski, Allan M Showalter |
| Journal | The New phytologist (New Phytol) Vol. 169 Issue 3 Pg. 479-92 ( 2006) ISSN: 0028-646X [Print] England |
| PMID | 16411951 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.) |
| Chemical References |
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