THE PLANT CELL, Vol 5, Issue 3 263-275, Copyright © 1993 by American Society of Plant Biologists
Ablation of Papillar Cell Function in Brassica Flowers Results in the Loss of Stigma Receptivity to Pollination
M. K. Kandasamy, M. K. Thorsness, S. J. Rundle, M. L. Goldberg, J. B. Nasrallah and M. E. Nasrallah
Section of Plant Biology, Division of Biological Sciences, Cornell University, Ithaca, New York 14853
Plant reproduction in crucifers is dependent on interactions that occur at
the stigma surface between the male gametophyte (pollen and pollen tube)
and papillar cells. To dissect these complex interactions, papillar cells
were genetically ablated by targeting the expression of a toxin to
appropriate cells of the flower with a flower-specific and developmentally
regulated promoter. In transgenic Brassica plants that expressed the toxic
gene fusion, flower morphology was normal except for aberrant papillar cell
development and partial pollen sterility. Microscopic, biochemical, and
functional analyses, mainly focused on papillar cell responses, revealed
that papillar cells lost their ability to elongate, to synthesize
cell-specific proteins, and to support pollen germination after self- or
cross-pollination. This loss of stigma receptivity to pollination was
mimicked by treating pistils with protein phosphatase inhibitors.
Differences in the effects of genetic and chemical ablation on the
pollination responses of Brassica and Arabidopsis flowers are discussed and
are ascribed in part to a requirement for phosphorylation/dephosphorylation
events in Brassica but not in Arabidopsis.
