Present address: Embrapa Genetic Research and Biotechnology, 70770-900 Brasilia, Brazil.
Sexual reproduction is the default mode in apomictic Hieracium subgenus Pilosella, in which two dominant loci function to enable apomixis
Article first published online: 26 APR 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 66, Issue 5, pages 890–902, June 2011
How to Cite
Koltunow, A. M. G., Johnson, S. D., Rodrigues, J. C. M., Okada, T., Hu, Y., Tsuchiya, T., Wilson, S., Fletcher, P., Ito, K., Suzuki, G., Mukai, Y., Fehrer, J. and Bicknell, R. A. (2011), Sexual reproduction is the default mode in apomictic Hieracium subgenus Pilosella, in which two dominant loci function to enable apomixis. The Plant Journal, 66: 890–902. doi: 10.1111/j.1365-313X.2011.04556.x
- Issue published online: 24 MAY 2011
- Article first published online: 26 APR 2011
- Accepted manuscript online: 21 MAR 2011 01:03PM EST
- Received 22 December 2010; revised 21 February 2011; accepted 23 February 2011; published online 26 March 2011.
Asexual seed formation, or apomixis, in the Hieracium subgenus Pilosella is controlled by two dominant independent genetic loci, LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP). We examined apomixis mutants that had lost function in one or both loci to establish their developmental roles during seed formation. In apomicts, sexual reproduction is initiated first. Somatic aposporous initial (AI) cells differentiate near meiotic cells, and the sexual pathway is terminated as AI cells undergo mitotic embryo sac formation. Seed initiation is fertilization-independent. Using a partially penetrant cytotoxic reporter to inhibit meioisis, we showed that developmental events leading to the completion of meiotic tetrad formation are required for AI cell formation. Sexual initiation may therefore stimulate activity of the LOA locus, which was found to be required for AI cell formation and subsequent suppression of the sexual pathway. AI cells undergo nuclear division to form embryo sacs, in which LOP functions gametophytically to stimulate fertilization-independent embryo and endosperm formation. Loss of function in either locus results in partial reversion to sexual reproduction, and loss of function in both loci results in total reversion to sexual reproduction. Therefore, in these apomicts, sexual reproduction is the default reproductive mode upon which apomixis is superimposed. These loci are unlikely to encode genes essential for sexual reproduction, but may function to recruit the sexual machinery at specific time points to enable apomixis.