Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/1999
Publication Date: N/A
Interpretive Summary: For decades, plant breeders have tried in vain to use the gene for asexual reproduction for rapidly creating new hybrid crops. Isolation of the gene for asexual reproduction (apomixis) would create a new green revolution. Using this gene as a tool in genetically engineered plants, plant breeders would be able to quickly move other important genes into crops and vegetables. Being able to create vigorous, healthy new hybrid fruits and vegetables with improved qualities such as flavor, color, and appearance could be done in one-third of the time it now takes. The grass species Cenchrus ciliare and Pennisetum squamulatum, closely related to grain crop pearl millet, provide model plants useful for obtaining the apomixis gene. In collaboration between scientists from the USDA (University Park, PA) and the University of Georgia (Tifton, GA), researchers have discovered five molecular DNA markers that are closely linked to the apomixis gene in each species. This paved the way for them to the discovery of an apomixis-specific genomic region that is highly conserved in the two species. This is another crucial step in locating the position of the gene on a plant chromosome, a necessary step to cloning the gene and placing it in high value crops through genetic engineering.
Technical Abstract: Apomixis is a unique mode of reproduction by which plants clonally propagate themselves through seeds (Asker and Jerling, 1992). In apomicts, meiosis is circumvented in the differentiation of the female gametophyte, and the megaspore mother cell or its meiotic derivatives degenerate (Nogler, 1984), In apospory, a form of gametophytic apomixis, an embryo sac cdifferentiates by mitotic division of a somatic cell within the ovule. Unreduced aposporous embryo sacs are easily distinguished in many apomictic grasses from normally reduced Polygonum-type sexual embryo sacs by the lack of antipodals (Young et al., 1979). These Panicum-type embryo sacs usually include four nuclei, which are partitioned into two synergids, once central cell and an egg cell. In this study, we tested the synteny of apospory- lined molecular markers (Ozias-Akins et al. 1998) in two species reproducing by apospory, Pennisetum squamulatum Fresen and Cenchrus ciliaris L. (=Pennisetum ciliare (L.) Link; buffelgrass).