Plant, Animal & Microbe Genomes X Conference Plant, Animal & Microbe Genomes X ConferenceJanuary 12-16, 2002
Town & Country Convention Center
San Diego, CA
Workshop: Apomixis
Apomixis is a reproductive process in certain species of flowering plants that circumvents meiosis and fertilization to result in the generation of genetically identical progeny. Apospory, a subtype of apomixis, occurs in a number of grass species as a consequence of the formation of unreduced embryo sacs from somatic nucellar cells. We previously showed, by molecular mapping of the apospory trait, that it is positioned in a region of the genome low in recombination. Since recombination is known to decrease in the vicinity of the centromere, the chromosomal location of the locus was explored by fluorescence in situ hybridization. BAC clones and or repetitive DNAs containing apomixis-linked markers were labeled and probed onto mitotic chromosome spreads of one or both apomictic plants under study, Pennisetum squamulatum and Cenchrus ciliaris. The position of the apomixis locus appears to be sub-telomeric in P. squamulatum and nearer to the centromere in C. ciliaris. Thus in spite of the high degree of conservation among the markers in these two species, the chromosomal location of the locus apparently has been rearranged during evolution. The size of the apomixis locus is still in the process of being determined by physical mapping of flanking recombinant markers. A chromosomal walk has been initiated to span the apospory specific genomic region (ASGR) with BAC clones. The identification of sequence duplications within the ASGR is likely to lead to challenges both in establishing a correct or true linear contig using FPC and in estimating physical distances and organization of the ASGR-linked BAC clones by FISH.