Sexual and asexual (apomictic) seed development in flowering plants: molecular, morphological and evolutionary relationships

Matthew R. Tucker; Anna M. G. Koltunow

doi:10.1071/FP09078

EVOLUTIONARY REVIEW

Previous Next Contents Vol 36(6)

Sexual and asexual (apomictic) seed development in flowering plants: molecular, morphological and evolutionary relationships

Matthew R. Tucker ^A and Anna M. G. Koltunow ^A ^B

+ Author Affiliations

- Author Affiliations

^A CSIRO Plant Industry, PO Box 350, Glen Osmond, SA 5064, Australia.

^B Corresponding author. Email: anna.koltunow@csiro.au

This paper is part of an ongoing series: ‘The Evolution of Plant Functions’.

Functional Plant Biology 36(6) 490-504 https://doi.org/10.1071/FP09078
Submitted: 7 April 2009 Accepted: 21 April 2009 Published: 1 June 2009

Abstract

Reproduction in the flowering plants (angiosperms) is a dynamic process that relies upon the formation of inflorescences, flowers and eventually seed. Most angiosperms reproduce sexually by generating gametes via meiosis that fuse during fertilisation to initiate embryo and seed development, thereby perpetuating the processes of adaptation and evolution. Despite this, sex is not a ubiquitous reproductive strategy. Some angiosperms have evolved an alternate form of reproduction termed apomixis, which avoids meiosis during gamete formation and leads to the production of embryos without paternal contribution. Therefore, apomixis results in the production of clonal progeny through seed. The molecular nature and evolutionary origin of apomixis remain unclear, but recent studies suggest that apomixis evolved from the same molecular framework supporting sex. In this review, we consider physical and molecular relationships between the two pathways, with a particular focus on the initial stages of female reproduction where apomixis deviates from the sexual pathway. We also consider theories that explain the origin of apomictic processes from sexual progenitors. Detailed characterisation of the relationship between sex and apomixis in an evolutionary and developmental sense is an important step towards understanding how apomixis might be successfully integrated into agriculturally important, but currently sexual crops.

Additional keywords: apomixis, evolution, Hieracium, ovule, reproduction.

Acknowledgements

We apologise to the many investigators who could not be cited in this review due to space restrictions. We especially thank John Bennett, Steve Swain, Susan Johnson and other members of the Koltunow laboratory for helpful comments and discussions. Research in the Koltunow laboratory is supported by a Department of Education, Science and Training (DEST) Australia–India grant.

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