Date of Award

Spring 1-1-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology & Evolutionary Biology

First Advisor

Pamela K. Diggle

Second Advisor

William E. Friedman

Third Advisor

David W. Stock

Fourth Advisor

William W. Adams III

Fifth Advisor

Anne W. Sylvester

Abstract

By studying cultivated maize and its wild closest relative, Balsas teosinte, I addressed two questions: 1) female gametophyte development and double fertilization in Balsas teosinte (Zea mays subsp. parviglumis), and 2) kin recognition within a seed: the effect of genetic relatedness of an endosperm to its compatriot embryo on maize seed development. First, over the course of maize evolution, domestication played a major role in the structural transition of the vegetative and reproductive characteristics that distinguish it from its closest wild relative, Balsas teosinte. Little is known, however, about impacts of the domestication process on the cellular features of the female gametophyte and the subsequent reproductive events after fertilization. The results show that the fertilization process of Balsas teosinte is basically similar to domesticated maize. In contrast with maize, many events associated with the development of the embryo and endosperm appear to be initiated earlier in Balsas teosinte. I propose that the relatively longer duration of the free nuclear endosperm phase in maize is correlated with the development of a larger fruit (kernel) and with a bigger endosperm compared with Balsas teosinte.

Second, as one of two sexually formed products resulting from double fertilization in angiosperms, the endosperm nourishes its compatriot embryo during seed development and/or germination and ultimately dies. Previous theoretical studies suggest that the coefficient of relatedness of an endosperm to an embryo in the same seed might determine the amount of resources ultimately available for the embryo during seed development. My results show that the degree of genetic relatedness of an endosperm to its compatriot embryo has a significant effect on embryo weight, but not on endosperm weight. Thus, the endosperm of heterofertilized seeds appears to behave less cooperatively with respect to resource transfer toward its less-closely-related embryo compared to those in homofertilized seeds. This study provides key insights into the developmental and cooperative interactions between the endosperm and embryo as affected by coefficients of relatedness.

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