PLANT PHYSIOLOGY , Vol 114, Issue 4 1523-1531, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Cell Wall Metabolism in Ripening Fruit (IX. Synthesis of Pectic and Hemicellulosic Cell Wall Polymers in the Outer Pericarp of Mature Green Tomatoes (cv XMT-22)
M. Huysamer, L. C. Greve and J. M. Labavitch
Department of Horticulture, University of Stellenbosch, Stellenbosch, South Africa (M.H.)
Discs of outer pericarp were excised from mature green tomato (Lycopersicon
esculentum Mill.) fruit and kept in sterile tissue culture plates for 4 d,
including 2 d of incubation with D-[U-13C]glucose. Cell walls were prepared
and the water-soluble, pectic, and hemicellulosic polymers were extracted.
Cell wall synthetic capacity was determined by gas chromatography-mass
spectrometry analysis of incorporation of the heavy isotope label. The
"outer" 2-mm pericarp region, which included the cuticle, had a lower cell
wall synthetic capacity than the "inner" 2-mm region immediately below it
(closer to the locules), based on the percentage of labeling of the neutral
sugars. There were no significant differences in relative abundance of
glycosidic linkages in the two tissue regions. Label was incorporated into
neutral sugars and linkages typical for each polysaccharide class were
identified in the cell wall preparations. Galacturonic acid and glucuronic
acid were labeled to an extent similar to that of the neutral sugars in
each tissue region.
