Journal Article

Temporal regulation of cell-wall pectin methylesterase and peroxidase isoforms in cadmium-treated flax hypocotyl

Florence Paynel, Annick Schaumann, Mustapha Arkoun, Olfa Douchiche and Claudine Morvan

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 104, issue 7, pages 1363-1372
Published in print December 2009 | ISSN: 0305-7364
Published online October 2009 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcp254
Temporal regulation of cell-wall pectin methylesterase and peroxidase isoforms in cadmium-treated flax hypocotyl

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

In hypocotyls of flax (Linum usitatissimum) cadmium-induced reorientation of growth (i.e. an increase in expansion and a decrease in elongation) coincides with marked changes in the methylesterification and cross-linking of homogalacturonans within various cell-wall (CW) domains. The aim of the present study was to examine the involvement of pectin methylesterase (PME) and peroxidase (PER) in this cadmium-induced CW remodelling.

Methods

CW proteins were extracted from hypocotyls of 10- and 18-d-old flax that had been treated or not treated with 0·5 mm Cd(NO3)2. PME and PER expression within these extracts was detected by LC/MS, by isoelectric focusing and enzyme activity assays. Transcript expression by RT-PCR of known flax PME and PER genes was also measured in corresponding samples.

Key Results

In cadmium-treated seedlings, PME activity increased as compared with controls, particularly at day 10. The increased activity of PME was accompanied by increased abundance of both a basic protein isoform (B2) and a particular transcript (Lupme5). In contrast, induction of PER activity by cadmium was highest at day 18. Among the four reported PER genes, Flxper1 and 3 increased in abundance in the presence of cadmium at day 18.

Conclusions

The temporal regulation of Lupme and Flxper genes and of their respective enzyme activities fits the previously reported cadmium-induced structural changes of homogalacturonans within the CWs. After PME-catalysed de-esterification of homogalacturonans, their cross-linking would depend on the activity of PERs interacting with calcium-dimerized blocks and reinforce the cell cohesion during the cadmium-induced swelling.

Keywords: Cadmium; cell wall; homogalacturonan; Linum usitatissimum; pectin methylesterase; peroxidase

Journal Article.  7032 words.  Illustrated.

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

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