Genetics, Vol. 165, 1521-1531, November 2003, Copyright © 2003
Heterochronic Expression of Sexual Reproductive Programs During Apomictic Development in Tripsacum
Daniel Grimanellia,b,
Marcelina Garcíab,
Etienne Kaszasc,
Enrico Perottib, and
Olivier Leblanca,b
a Institut de Recherche pour le Développement (IRD), 06600 Mexico DF, México
b International Maize and Wheat Improvement Center (CIMMYT), 06600 Mexico DF, México
c Syngenta Biotechnology, Research Triangle Park, North Carolina 27709
Corresponding author:
Daniel Grimanelli, Department of Applied Biotechnology, CIMMYT APDO 6-641, 06600 México DF, México., dgrimanelli{at}cgiar.org (E-mail)
Communicating editor: J. BIRCHLER
Some angiosperms reproduce by apomixis, a natural way of cloning through seeds. Apomictic plants bypass both meiosis and egg cell fertilization, producing progeny that are genetic replicas of the mother plant. In this report, we analyze reproductive development in Tripsacum dactyloides, an apomictic relative of maize, and in experimental apomictic hybrids between maize and Tripsacum. We show that apomictic reproduction is characterized by an alteration of developmental timing of both sporogenesis and early embryo development. The absence of female meiosis in apomictic Tripsacum results from an early termination of female meiosis. Similarily, parthenogenetic development of a maternal embryo in apomicts results from precocious induction of early embryogenesis events. We also show that male meiosis in apomicts is characterized by comparable asynchronous expression of developmental stages. Apomixis thus results in an array of possible phenotypes, including wild-type sexual development. Overall, our observations suggest that apomixis in Tripsacum is a heterochronic phenotype; i.e., it relies on a deregulation of the timing of reproductive events, rather than on the alteration of a specific component of the reproductive pathway.
