Aligning Physical and Functional Maps of a Genomic Region Spanning the Apomixis Locus by Exploiting Model Cereal Genomics

University Of Georgia Research Foundation Inc, Athens GA

Investigators

Abstract

Apomixis, defined as asexual reproduction through seed, is widespread among angiosperm families although 75% of the apomictic species are found in three plant families, Poaceae, Rosaceae, and Asteraceae. The plant materials examined in this proposal are members of the Poaceae family, the most important crop plant family in the human food chain. All crop plants in this family reproduce sexually, although wild relatives of maize, wheat, and pearl millet may undergo asexual (apomictic) reproduction. Seeds formed on an apomictic plant contain genetically identical embryos, thus the trait has significant potential for preserving hybrid vigor from one generation to the next in highly productive crop plant genotypes. In Pennisetum squamulatum and Cenchrus ciliaris meiosis typically aborts and unreduced aposporous embryo sacs form from nucellar cells. Genetic mapping studies in Pennisetum have revealed that the locus for the formation of unreduced embryo sacs resides in a chromosomal region with a low recombination rate. Based on genetic map information, positional cloning of gene(s) responsible for apomictic reproduction in Pennisetum is in progress. Transcriptional mapping will use the tools that have been developed for physical mapping of this region and will also use the well developed molecular tools from related diploid model species such as sorghum and rice. The exploration of colinearity in this region between two model diploids and two apomictic species will focus on highly conserved gene sequences. Candidate reproductive or novel genes in this region will be compared for their expression profiles among apomictic and sexual genotypes/species. This research will provide an example of the transfer of genomic information from small-genome grasses to non-recombining regions of large-genome species.