Developmental and Structural Section
Wu, Chi-Chih , Diggle, Pamela , Friedman, William .
The impact of the lower genetic relatedness of endosperm to its compatriot embryo on maize seed development.
In most flowering plants, a developing seed commonly contains an embryo and an endosperm. As a result of double fertilization the embryo and endosperm within a seed are identical in terms of allele identities but commonly differ in ploidy. In contrast with an embryo, endosperm does not transmit its genetic contents to the next generation. Rather, an endosperm nourishes its compatriot embryo during seed development and germination, and ultimately dies. Evolutionary models based on kin selection suggest that the "sacrifice" of an endosperm for the benefit of its embryo may be advantageous because of the greater coefficient of relatedness of the endosperm to its associated embryo than to other embryos. To empirically test such theoretical interpretations, we took advantage of the phenomenon of heterofertilization in maize, in which double fertilization is accomplished by sperm from two genetically distinct pollen grains, and the embryo and endosperm have different fathers. Because the coefficient of relatedness between an embryo and its compatriot endosperm is lower in heterofertilized kernels (seeds) than in homofertilized kernels, inclusive fitness theory predicts that in heterofertilized kernels the endosperm might behave less cooperatively with its embryo with the result that the embryo would be relatively smaller than in homofertilized kernels. We used five genetically distinct maize lines and a crossing design that allowed us to control for genetic background effects. Dry masses of dissected embryo and endosperm of heterofertilized and adjacent homofertilized kernels were compared. Preliminary results show that the dry weight of endosperm is not significantly different between heterofertilized and homofertilized kernels, but the weight of the embryo of heterofertilized kernels is slightly decreased. The lower weight of embryos in heterofertilized kernels is consistent with our prediction: endosperm behaves less cooperatively and provides less nourishment to its compatriot embryo in heterofertilized kernels than in homofertilized kernels.
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1 - University Of Colorado Boulder, Campus Box 334, Boulder, CO, 80309, USA
2 - University of Colorado , Ecology and Evolutionary Biology, Ramaley N122 , Boulder , CO, 80309-0334, USA
3 - Harvard University and Arnold Arboretum, Organismic and Evolutionary Biology, Cambridge, MA, USA
coefficient of relatedness.
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell A/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 4:30 PM