THE PLANT CELL, Vol 6, Issue 6 789-798, Copyright © 1994 by American Society of Plant Biologists
Activation of Basal Cells of the Apical Meristem during Sepal Formation in Tomato
A. J. Fleming and C. Kuhlemeler
Institute of Plant Physiology, University of Berne, Altenbergrain 21, CH-3013 Berne, Switzerland
Although great advances have been made in research on the regulation of
primordium fate in the floral meristem, our understanding of the molecular
events occurring during the floral transition remains incomplete. Via a
careful analysis of the expression patterns of five genes encoding
housekeeping functions during the floral transition in tomato (using both
in situ hybridization and enzyme histochemistry), we identified a
particular phase of floral development (sepal initiation) at which cells
located toward the base of the meristem show a high level of cellular
metabolism, whereas cells at the tip of the meristem dome show little
activity. At other stages of floral development, the probes used showed
genespecific patterns of expression generally consistent with our previous
investigation of the vegetative apical meristem. Our data, in conjunction
with other reports in the literature, enabled us to postulate that relative
activation of basal cells of the meristem may be of general occurrence
during the transition to flowering. Such a hypothesis could account for
recent observations using periclinal chimeras on the effect of L3 genotypes
on flower development and have a bearing on the expected mechanism by which
the number of primordia generated by a floral meristem is regulated.
