Plant & Animal Genomes XVII Conference

January 10-14, 2009
Town & Country Convention Center
San Diego, CA

Genetic, Cytological And Expression Analyses For Apomixis Study In Guineagrass (Panicum maximum)

Yukio Akiyama¹ , Hitomi Yamada-Akiyama¹ , Peggy Ozias-Akins² , Wayne W. Hanna³ , Hitoshi Nakagawa^1,4 , Tadashi Takamizo¹ , Manabu Takahara¹ , Shin-ichi Sugita¹ , Masumi Ebina¹

¹  National Agriculture and Food Research Organization, National Institute of Livestock and Grassland Science, Nasushiobara, 329-2793 Japan

²  University of Georgia Tifton Campus, Department of Horticulture, Tifton, GA 31793-0748 USA

³  University of Georgia Tifton Campus, Department of Crop and Soil Science, Tifton, GA 31793-0748 USA

⁴  The Institute of Radiation Breeding, National Institute of Agrobiological Sciences, Hitachi-Ohmiya, 319-2293 Japan

Apomixis is a mode of asexual reproduction which produces progeny as maternal clones through seed without chromosomal recombination. Apospory is a form of gametophytic apomixis where the embryo sac arises directly from a somatic cell of the ovary. It is known that there is segregation distortion at the locus (loci) related to apospory in many species, the recombinationally inert region linked to apospory is named the apospory-specific genomic region (ASGR). Detailed analysis of the ASGR is important to facilitate identification of the gene(s) governing apospory. Guineagrass (Panicum maximum) is one of the most important tropical forage grasses and known to have both facultative aposporous and obligate sexual modes of reproduction. 34 AFLP markers linked to apospory were identified and showed no recombination among 72 individuals. 242 AFLP markers were identified in the species by bulk segregant analysis with 10 F₁ progeny in each bulk representing apomictic or sexual phenotypes. 118 BAC clones were isolated using AFLP markers from the apomict bulk of which 12 were physically mapped by fluorescence in situ hybridization (FISH) on only one chromosome in the genome of the aposporous accession, but not in the sexual. These results indicate existence of an ASGR in P. maximum. Expression analyses using a small scale microarray, RT-PCR and Q-PCR detected three genes specifically expressed in the aposporous tissues. BAC clones for physical mapping were isolated by screening with STS markers converted from the ESTs. Moreover, EST libraries including ~10,000 unigenes have been constructed to make custom microarray on a large scale feasible. Genetic, cytological and expression analyses for apomixis study in P. maximum will be discussed in the presentation. This research was supported by the PROBRAIN.