Plant & Animal Genomes XVI Conference

January 12-16, 2008
Town & Country Convention Center
San Diego, CA

Apomixis In Pennisetum squamulatum: Identification And Characterization Of Apomictic Candidate Genes

Joann A Conner¹ , Heqiang Huo¹ , Manjit Singh¹ , Yajuan Zeng¹ , Emidio Albertini³ , Wayne W Hanna² , Peggy Ozias-Akins¹

¹  Department of Horticulture, University of Georgia Tifton Campus, Tifton, GA 31793 USA

²  Department of Crop and Soil Sciences, University of Georgia Tifton Campus, Tifton, GA 31793 USA

³  Plant Biology, Agroenvironmental and Animal Biotechnology Department, University of Perugia, Perugia 06121 Italy

Apomixis is a naturally occurring mode of asexual reproduction in flowering plants. Pennisetum squamulatum reproduces by apospory, a gametophytic form of apomixis. Within the ovules of P. squamulatum, female meiosis is aborted and aposporous embryo sac(s) are formed from surrounding somatic nucellar cells. The genomic region associated with apospory (the apospory-specific genomic region or ASGR) has been genetically and cytogenetically characterized in P. squamulatum. The ASGR is physically large (>50 Mb) and heterochromatic in nature. BAC clones derived from the ASGR were partially sequenced and analyzed for gene content. One transcriptionally active gene of interest is the ASGR-BABY BOOM-like (ASGR-BBM) gene. ASGR-BBM encodes a 545 amino acid protein containing two AP2 domains which are 96% similar to the AP2 domains of the Brassica napus BBM gene. The BnBBM gene is induced in microspore cultures of B. napus undergoing somatic embryogenesis while in Arabidopsis AtBBM is expressed in developing embryos. The role of ASGR-BBM is being explored by conducting RNA silencing studies in transgenic F1 apomictic plants and through analysis of the ASGR-BBM-like genes in Cenchrus ciliaris a close apomictic relative of P. squamulatum. Identification of additional genes at the ASGR is being pursued through the sequence analysis of low copy sequences derived from a DOP-PCR library of the microdissected ASGR-carrier chromosome from P. squamulatum.