Journal Article

Tension required for pectate chemistry to control growth in <i>Chara corallina</i>

Timothy E. Proseus and John S. Boyer

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 15-16, pages 4283-4292
Published in print December 2007 | ISSN: 0022-0957
Published online December 2007 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/erm318

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Recent work showed that polygalacturonate (pectate) chemistry controlled the growth rate of the large-celled alga Chara corallina when turgor pressure (P) was normal (about 0.5 MPa). The mechanism involved calcium withdrawal from the wall by newly supplied pectate acting as a chelator. But P itself can affect growth rate. Therefore, pectate chemistry was investigated at various P. A pressure probe varied P in isolated walls, varying the tension on the calcium pectate cross-links bearing the load of P. When soluble pectate was newly supplied, the wall grew irreversibly but the pectate was inactive below a P of 0.2 MPa, indicating that tension was required in the existing wall before new pectate acted. It was suggested that the tension distorted some of the wall pectate (the dominant pectin), weakening its calcium cross-links and causing the calcium to be preferentially lost to the new pectate, which was not distorted. The preferential loss provided a molecular mechanism for loosening the wall structure, resulting in faster growth. However, the resulting relaxation of the vacated wall pectate would cause calcium to be exchanged with load-bearing calcium pectate nearby, auto-propagating throughout the wall for long periods. There is evidence for this effect in isolated walls. In live cells, there is also evidence that auto-propagation is controlled by binding the newly supplied pectate (now calcium pectate) to the wall and/or by additional Ca2+ entering the wall structure. A tension-dependent cycle of pectate chemistry thus appeared to control growth while new wall was deposited as a consequence.

Keywords: Cell enlargement; cell wall; pectin; turgor pressure

Journal Article.  6280 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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