Journal Article

Localization of sucrose synthase in developing seed and siliques of <i>Arabidopsis thaliana</i> reveals diverse roles for SUS during development

Hossein Fallahi, Graham N. Scofield, Murray R. Badger, Wah Soon Chow, Robert T. Furbank and Yong-Ling Ruan

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 12, pages 3283-3295
Published in print September 2008 | ISSN: 0022-0957
Published online July 2008 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/ern180

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This study investigated the roles of sucrose synthase (SUS) in developing seeds and siliques of Arabidopsis thaliana. Enzyme activity assays showed that SUS activity was highest in developing whole siliques and young rosette leaves compared with other tissues including mature leaves, stems, and flowers. Surprisingly, quantitative PCR analyses revealed little correlation between SUS activity and transcript expression, which indicated the importance of examining the role of SUS at the protein level. Therefore, immunolocalization was performed over a developmental time course to determine the previously unreported cellular localization of SUS in Arabidopsis seed and silique tissues. At 3 d and 10 d after flowering (daf), SUS protein localized to the silique wall, seed coat, funiculus, and endosperm. By 13 daf, SUS protein was detected in the embryo and aleurone layer, but was absent from the seed coat and funiculus. Starch grains were also present in the seed coat at 3 and 10 daf, but were absent at 13 daf. Co-localization of SUS protein and starch grains in the seed coat at 3 and 10 daf indicates that SUS may be involved in temporary starch deposition during the early stages of seed development, whilst in the later stages SUS metabolizes sucrose in the embryo and cotyledon. Within the silique wall, SUS localized specifically to the companion cells, indicating that SUS activity may be required to provide energy for phloem transport activities in the silique wall. The results highlight the diverse roles that SUS may play during the development of silique and seed in Arabidopsis.

Keywords: Arabidopsis; companion cells; immunolocalization; nectary; seed development; silique wall; sucrose synthase

Journal Article.  7434 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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