Journal Article

Physiological and proteomic characterization of manganese sensitivity and tolerance in rice (<i>Oryza sativa</i>) in comparison with barley (<i>Hordeum vulgare</i>)

Hendrik Führs, Christof Behrens, Sébastien Gallien, Dimitri Heintz, Alain Van Dorsselaer, Hans-Peter Braun and Walter J. Horst

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 105, issue 7, pages 1129-1140
Published in print June 2010 | ISSN: 0305-7364
Published online March 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq046
Physiological and proteomic characterization of manganese sensitivity and tolerance in rice (Oryza sativa) in comparison with barley (Hordeum vulgare)

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Background and Aims

Research on manganese (Mn) toxicity and tolerance indicates that Mn toxicity develops apoplastically through increased peroxidase activities mediated by phenolics and Mn, and Mn tolerance could be conferred by sequestration of Mn in inert cell compartments. This comparative study focuses on Mn-sensitive barley (Hordeum vulgare) and Mn-tolerant rice (Oryza sativa) as model organisms to unravel the mechanisms of Mn toxicity and/or tolerance in monocots.

Methods

Bulk leaf Mn concentrations as well as peroxidase activities and protein concentrations were analysed in apoplastic washing fluid (AWF) in both species. In rice, Mn distribution between leaf compartments and the leaf proteome using 2D isoelectic focusing IEF/SDS–PAGE and 2D Blue native BN/SDS–PAGE was studied.

Key Results

The Mn sensitivity of barley was confirmed since the formation of brown spots on older leaves was induced by low bulk leaf and AWF Mn concentrations and exhibited strongly enhanced H2O2-producing and consuming peroxidase activities. In contrast, by a factor of 50, higher Mn concentrations did not produce Mn toxicity symptoms on older leaves in rice. Peroxidase activities, lower by a factor of about 100 in the rice leaf AWF compared with barley, support the view of a central role for these peroxidases in the apoplastic expression of Mn toxicity. The high Mn tolerance of old rice leaves could be related to a high Mn binding capacity of the cell walls. Proteomic studies suggest that the lower Mn tolerance of young rice leaves could be related to Mn excess-induced displacement of Mg and Fe from essential metabolic functions.

Conclusions

The results provide evidence that Mn toxicity in barley involves apoplastic lesions mediated by peroxidases. The high Mn tolerance of old leaves of rice involves a high Mn binding capacity of the cell walls, whereas Mn toxicity in less Mn-tolerant young leaves is related to Mn-induced Mg and Fe deficiencies.

Keywords: Apoplast; compartmentation; Hordeum vulgare ‘Baroness’; Mn sensitivity; Mn tolerance; Oryza sativa var. japonica ‘Guara’; proteome; photosynthesis

Journal Article.  7821 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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