Sexual and Apomictic Reproduction in Hieracium Subgenus Pilosella Are Closely Interrelated Developmental Pathways

• Published in: The Plant cell Vol. 15; no. 7; pp. 1524 - 1537
• Main Authors: Tucker, Matthew R., Araujo, Ana-Claudia G., Paech, Nicholas A., Hecht, Valerie, Ed D. L. Schmidt, Rossell, Jan-Bart, de Vries, Sacco C., Anna M. G. Koltunow
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Biologists 01-07-2003
• Subjects: Amino Acid Sequence; Apomixis; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Asteraceae - cytology; Asteraceae - genetics; Asteraceae - growth & development; Cell nucleus; Embryo sac; Embryos; Endosperm; Flowering plants; Flowers - cytology; Flowers - genetics; Flowers - growth & development; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Glucuronidase - genetics; Glucuronidase - metabolism; In Situ Hybridization; Megaspores; Megasporocytes; Meiosis - genetics; Molecular Sequence Data; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Ovules; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants, Genetically Modified; Protein Kinases - genetics; Protein Kinases - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Repressor Proteins - genetics; Repressor Proteins - metabolism; Reproduction - genetics; Reproduction - physiology; Seeds; Seeds - cytology; Seeds - genetics; Seeds - growth & development; Sequence Homology, Amino Acid; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.011742

Seed formation in flowering plants requires meiosis of the megaspore mother cell (MMC) inside the ovule, selection of a megaspore that undergoes mitosis to form an embryo sac, and double fertilization to initiate embryo and endosperm formation. During apomixis, or asexual seed formation, in Hieracium ovules, a somatic aposporous initial (AI) cell divides to form a structurally variable aposporous embryo sac and embryo. This entire process, including endosperm development, is fertilization independent. Introduction of reproductive tissue marker genes into sexual and apomictic Hieracium showed that AI cells do not express a MMC marker. Spatial and temporal gene expression patterns of other introduced genes were conserved commencing with the first nuclear division of the AI cell in apomicts and the mitotic initiation of embryo sac formation in sexual plants. Conservation in expression patterns also occurred during embryo and endosperm development, indicating that sexuality and apomixis are interrelated pathways that share regulatory components. The induction of a modified sexual reproduction program in AI cells may enable the manifestation of apomixis in Hieracium.