Immunogold labelling indicates high catalase concentrations in amorphous and crystalline inclusions of sunflower (Helianthus annuus L.) peroxisomes |
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Authors: | Klaus Bernhard Tenberge and Rainer Eising |
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Institution: | (1) Institut für Botanik, Westf?lische Wilhelms-Universit?t, Schloβgarten 3, D-48149 Münster, Germany |
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Abstract: | Summary Immunogold labelling and electron microscopy were used to investigate whether catalase was present in peroxisomal inclusions,
the composition of which has not yet been determined in plant cells. In the mesophyll cells of sunflower (Helianthus annuus L.) cotyledons, the catalase gold label was confined to peroxisomes. At day 2 of postgerminative growth in darkness, peroxisomes
were free of inclusions, and the matrix was homogeneously labelled with gold particles. Thereafter, amorphous inclusions appeared,
but by day 5 of growth, conspicuous crystalline inclusions (cores) were the predominant type. This developmental change, first
observed in cotyledons grown in continuous light between day 2.5 and 5, also took place in cotyledons kept in permanent darkness.
Both amorphous and crystalline inclusions showed a much higher immunogold label than did the peroxisomal matrix, indicating
that catalase was a component of both types of peroxisomal inclusions. In contrast to catalase, the immunogold label of glycolate
oxidase was almost completely absent from cores and was confined to the peroxisomal matrix. Together with reports on the absence
of other enzymes from peroxisomal inclusions in sunflower and other species (Vaughn, 1989) our results suggest that catalase
is a major constituent of amorphous and crystalline peroxisomal inclusions in plants. |
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