Lafleur, Edith , Kapfer, Christelle , Gray-Mitsumune, Madoka , Matton, Daniel P. .
Involvement of the Solanum chacoense MAPKKK ScFRK1 in embryo sac development.
The Solanum chacoense Fertilization-Related Kinase 1 is a member of the MEKK subfamily of plant MAPKKK that is specifically expressed in ovules. RNA gel blot analysis showed that ScFRK1 mRNA levels decrease rapidly following pollination. In situ hybridization showed that ScFRK1 mRNAs accumulate predominantly at the distal end (tip) of the growing integument during early ovule development. Later, ScFRK1 expression is almost exclusively detected in the egg apparatus cells of the embryo sac. These results suggest both pre- and post-fertilization roles in ovule development. Transgenic plants down-regulated in ScFRK1 expression showed no abnormal phenotypes in vegetative tissues but produced seedless fruits upon pollination. To define where and when during ovule development abnormalities appeared, cleared ovules from affected transgenic lines were observed by differential interference contrast. At anthesis, higher frequency of abnormal embryo sacs correlated with lower ScFRK1 expression in these transgenic lines, confirming the link between ScFRK1 expression and the formation of a functional embryo sac. Using flower buds at various developmental stages it was possible to show that in plants weakly expressing the ScFRK1 gene, formation of the female gametophyte did not progress further than the functional megaspore stage (FG1). No further divisions were observed, leading to the formation of ovules devoid of an embryo sac. Surprisingly, even in severely affected plants producing no embryo sac, pollination led to the production of parthenocarpic fruits. Using a semi in vivo pollen tube growth system ScFRK1 mutant lines were also shown to be severely affected in pollen tube guidance, confirming the involvement of the egg apparatus cells as the source of attracting molecules.
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1 - Université de Montréal - IRBV, Sciences biologiques, 4101 Sherbrooke est, Montreal, Quebec, H1X2B2, Canada
2 - Université de Montréal - IRBV, Sciences biologiques
Embryo sac development
pollen tube guidance
Presentation Type: ASPB Minisymposium
Location: International Ballroom/Hilton
Date: Tuesday, July 10th, 2007
Time: 4:10 PM