PLANT PHYSIOLOGY , Vol 106, Issue 2 575-581, Copyright © 1994 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Cell Wall Metabolism in Ripening Fruit (VII. Biologically Active Pectin Oligomers in Ripening Tomato (Lycopersicon esculentum Mill.) Fruits)
E. Melotto, L. C. Greve and J. M. Labavitch
Pomology Department, University of California, Davis California 95616
A water-soluble, ethanol-insoluble extract of autolytically inactive tomato
(Lycopersicon esculentum Mill.) pericarp tissue contains a series of
galacturonic acid-containing (pectic) oligosaccharides that will elicit a
transient increase in ethylene biosynthesis when applied to pericarp discs
cut from mature green fruit. The concentration of these oligosaccharides in
extracts (2.2 [mu]g/g fresh weight) is in excess of that required to
promote ethylene synthesis. Oligomers in extracts of ripening fruits were
partially purified by preparative high-performance liquid chromatography,
and their compositions are described. Pectins were extracted from cell
walls prepared from mature green fruit using chelator and Na2CO3 solutions.
These pectins are not active in eliciting ethylene synthesis. However,
treatment of the Na2CO3-soluble, but not the chelator-soluble, pectin with
pure tomato polygalacturonase 1 generates oligomers that are similar to
those extracted from ripening fruit (according to high-performance liquid
chromatography analysis) and are active as elicitors. The possibility that
pectin-derived oligomers are endogenous regulators of ripening is
discussed.
