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Lookup NU author(s): Dr Phlippus Van Heerden, Professor Christine Foyer
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The roles of cysteine proteinases (CP) in leaf protein accumulation and composition were investigated in transgenic tobacco (Nicotiana tabacum L.) plants expressing the rice cystatin, OC-1. The OC-1 protein was present in the cytosol, chloroplasts, and vacuole of the leaves of OC-1 expressing (OCE) plants. Changes in leaf protein composition and turnover caused by OC-1-dependent inhibition of CP activity were assessed in 8-week-old plants using proteomic analysis. Seven hundred and sixty-five soluble proteins were detected in the controls compared to 860 proteins in the OCE leaves. A cyclophilin, a histone, a peptidyl-prolyl cis-trans isomerase, and two ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase isoforms were markedly altered in abundance in the OCE leaves. The senescence-related decline in photosynthesis and Rubisco activity was delayed in the OCE leaves. Similarly, OCE leaves maintained higher leaf Rubisco activities and protein than controls following dark chilling. Immunogold labelling studies with specific antibodies showed that Rubisco was present in Rubisco vesicular bodies (RVB) as well as in the chloroplasts of leaves from 8-week-old control and OCE plants. Western blot analysis of plants at 14 weeks after both genotypes had flowered revealed large increases in the amount of Rubisco protein in the OCE leaves compared to controls. These results demonstrate that CPs are involved in Rubisco turnover in leaves under optimal and stress conditions and that extra-plastidic RVB bodies are present even in young source leaves. Furthermore, these data form the basis for a new model of Rubisco protein turnover involving CPs and RVBs. © The Author [2008]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved.
Author(s): Prins A, Van Heerden PDR, Olmos E, Kunert KJ, Foyer CH
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: Journal of Experimental Botany: 14th International Congress of Photosynthesis
Year of Conference: 2008
Pages: 1935-1950
ISSN: 0022-0957
Publisher: Oxford University Press
URL: http://dx.doi.org/10.1093/jxb/ern086
DOI: 10.1093/jxb/ern086
Library holdings: Search Newcastle University Library for this item
ISBN: 14602431
