Journal Article

Evidence for a tonoplast‐associated form of sucrose synthase and its potential involvement in sucrose mobilization from the vacuole

Ed Etxeberria and Pedro Gonzalez

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 54, issue 386, pages 1407-1414
Published in print May 2003 | ISSN: 0022-0957
Published online May 2003 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/erg148
Evidence for a tonoplast‐associated form of sucrose synthase and its potential involvement in sucrose mobilization from the vacuole

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The following work presents new evidence for a tonoplast localization of sucrose synthase and its functional role during the mobilization of vacuolar sucrose. Highly purified tonoplast vesicles were associated with significant SuSy levels as determined by immuno‐recognition, enzymatic activity, and by‐product measurements. Total tonoplast‐bound SuSy was estimated to be approximately 7% of the total tissue activity. SuSy affinity to the tonoplast was confirmed by the lack of SuSy displacement by ionic washes and also by the tonoplast ability to bind to exogenously added SuSy as compared to the cytosolic marker alcohol dehydrogenase. UL‐[14C]sucrose‐loaded vesicles incubated with ATP and UDP produced [14C]UDP‐Glc as determined by UDP‐Glc dehydrogenase and by the ability of the product to bind to DEAE‐cellulose and to co‐migrate with authentic UDP‐Glc on TLC. ATP alone induced sucrose efflux but not the production of [14C]ADP‐Glc. Kinetic analysis of [14C]UDPG formation under conditions of low sucrose availability suggests sucrose channelling between the ATP‐dependent sucrose transporter and SuSy, thus corroborating the association of SuSy with the tonoplast and its involvement in sucrose mobilization from the vacuole.

Keywords: Key words: Red beet, sucrose efflux, sucrose mobilization, sucrose synthase, tonoplast transport.

Journal Article.  5185 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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