title: Evolution of apomixis loci in Pilosella and Hieracium (Asteraceae) inferred from the conservation of apomixis-linked markers in natural and experimental populations.
abstract: The Hieracium and Pilosella (Lactuceae, Asteraceae) genera of closely related hawkweeds contain species with two different modes of gametophytic apomixis (asexual seed formation). Both genera contain polyploid species, and in wild populations, sexual and apomictic species co-exist. Apomixis is known to co-exist with sexuality in apomictic Pilosella individuals, however, apomictic Hieracium have been regarded as obligate apomicts. Here, a developmental analysis of apomixis within 16 Hieracium species revealed meiosis and megaspore tetrad formation in 1 to 7% of ovules, for the first time indicating residual sexuality in this genus. Molecular markers linked to the two independent, dominant loci LOSS OF APOMEIOSIS (LOA) and LOSS OF PARTHENOGENESIS (LOP) controlling apomixis in Pilosella piloselloides subsp. praealta were screened across 20 phenotyped Hieracium individuals from natural populations, and 65 phenotyped Pilosella individuals from natural and experimental cross populations, to examine their conservation, inheritance and association with reproductive modes. All of the tested LOA and LOP-linked markers were absent in the 20 Hieracium samples irrespective of their reproductive mode. Within Pilosella, LOA and LOP-linked markers were essentially absent within the sexual plants, although they were not conserved in all apomictic individuals. Both loci appeared to be inherited independently, and evidence for additional genetic factors influencing quantitative expression of LOA and LOP was obtained. Collectively, these data suggest independent evolution of apomixis in Hieracium and Pilosella and are discussed with respect to current knowledge of the evolution of apomixis.
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Plant Industry, Waite Campus, Glen Osmond, SA, Australia.
authors.forename: M L
authors.initials: ML
authors.lastname: Hand
authors.affiliation: Institute of Botany, Academy of Sciences of the Czech Republic, Zámek 1, Průhonice, Czech Republic.
authors.forename: P
authors.initials: P
authors.lastname: Vít
authors.affiliation: Institute of Botany, Academy of Sciences of the Czech Republic, Zámek 1, Průhonice, Czech Republic.
authors.forename: A
authors.initials: A
authors.lastname: Krahulcová
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Plant Industry, Waite Campus, Glen Osmond, SA, Australia.
authors.forename: S D
authors.initials: SD
authors.lastname: Johnson
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Plant Industry, Waite Campus, Glen Osmond, SA, Australia.
authors.forename: K
authors.initials: K
authors.lastname: Oelkers
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Plant Industry, Waite Campus, Glen Osmond, SA, Australia.
authors.forename: H
authors.initials: H
authors.lastname: Siddons
authors.affiliation: 1] Institute of Botany, Academy of Sciences of the Czech Republic, Zámek 1, Průhonice, Czech Republic [2] Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Chrtek
authors.affiliation: Institute of Botany, Academy of Sciences of the Czech Republic, Zámek 1, Průhonice, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Fehrer
authors.affiliation: Commonwealth Scientific and Industrial Research Organization (CSIRO) Plant Industry, Waite Campus, Glen Osmond, SA, Australia.
authors.forename: A M G
authors.initials: AM
authors.lastname: Koltunow
mesh_terms: D060832:Apomixis / Q000235:genetics*; D019659:Asteraceae / Q000235:genetics*; D005075:Biological Evolution; D017124:Conserved Sequence; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D056426:Genetic Loci; D005819:Genetic Markers; D005828:Genetics, Population; D006239:Haplotypes; D040582:Inheritance Patterns; D008969:Molecular Sequence Data; D012639:Seeds / Q000235:genetics
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant; D005819:Genetic Markers