Plant & Animal Genomes XVI Conference

January 12-16, 2008
Town & Country Convention Center
San Diego, CA

Apomixis In Eukaryotes, An Ancient Phenomenon

Dominique Roche¹ , John G. Carman²

¹  Caisson Laboratories, 1740 Research Park Way, North Logan, UT 84341, USA

²  Plants, Soils & Climate Department, Utah State University, Logan, UT 84322-4820, USA

We review all types of apomixis in eukaryotes. We define apomixis as the production of a progeny organism with an identical genetic makeup to its immediate progenitor organism through: i) production of non-recombined and unreduced spores, ii) spore differentiation into mating types, gametes or gametophytes, and iii) parthenogenetic development into the normal diploid life form. With this strict definition, the encumbered terminology of zoologists and botanists used to describe diverse and varied forms of reproduction in eukaryotes is superfluous to a holistic view of apomixis. We focus on evidences of hybridization stimulating the expression of apomixis in diverse eukaryotic taxa. Hybridization is used as an argumentative tool to illustrate differences in epigenetic tags of two hybridizing genomes, which lead to the production of unreduced gametes in hybrids. Parthenogenesis of unreduced mating types, gametes or gametophytes will then be discussed in terms of “erase and rebuild” processes involving polycomb proteins and cytoplasmic factors required for spindle assembly during the first mitotic division of an unreduced mating type or gamete. The extent to which these various mechanisms are involved in the origins of apomixis may differ between diploids and polyploids. Apomixis appears to be of ancient origin, and several of its mechanisms appear to be conserved among eukaryotes. Hence, apomixis may resurface in many taxa when the tight control of meiosis is altered. We hypothesize that the ‘sensing’ of an upcoming faulty meiosis may be a trigger for apomixis in many taxa.