Journal Article

Analysis of the Feed-Forward Effects of Sink Activity on the Photosynthetic Source-Sink Balance in Single-Rooted Sweet Potato Leaves. I. Activation of RuBPcase through the Development of Sinks

Shinichi Sawada, Makiko Sato, Akihito Kasai, Daisuke Yaochi, Youjiro Kameya, Izumi Matsumoto and Minobu Kasai

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 44, issue 2, pages 190-197
Published in print February 2003 | ISSN: 0032-0781
Published online February 2003 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcg024
Analysis of the Feed-Forward Effects of Sink Activity on the Photosynthetic Source-Sink Balance in Single-Rooted Sweet Potato Leaves. I. Activation of RuBPcase through the Development of Sinks

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Single-rooted sweet potato leaves having a petiole with a fragment of stem allocated exceptionally large amounts of photosynthates to tuberous roots, the only major storage organ, throughout an experimental period of 50 d. The increase in photosynthetic activity for CO2 fixation depended exclusively on the development of sink activity due to the growth of tuberous roots. Thus this model expressed a remarkable feed-forward effect on the photosynthetic source-sink balance. The level of ribulose-1,5-bisphosphate carboxylase (RuBPcase) protein in the leaves increased continuously during the period. The lowered initial as well as total activity of RuBPcase observed at the start of the experiment was raised with the cancellation of the sink-limited state due to the development of tuberous roots. The maximum activity determined after removing some inhibitor(s) from the enzyme by treating the leaf extract with SO42– was much greater than the total activity and remained approximately constant throughout the experimental period. The clear decrease in the difference between maximum and total activities with the development of tuberous roots might reflect the reactivation of RuBPcase due to the removal of some inhibitor(s) from the enzyme through the cancellation of the sink-limited state.

Keywords: Keywords: Feed-forward effects —Ipomoea batatas Lam. —Photosynthetic activity — Ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) — Single-rooted leaf — Source-sink balance.; Abbreviations: CA1P, 2-carboxy-d-arabinitol-1-phosphate; RuBP, ribulose-1,5-bisphosphate; RuBPcase, ribulose-1,5-bisphosphate carboxylase.

Journal Article.  5033 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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