Plant & Animal Genomes XV Conference

January 13-17, 2007
Town & Country Convention Center
San Diego, CA

Do Candidate Genes For Apomixis From Poa pratensis Also Play Important Roles In Other Apomicts And In The Sexual Arabidopsis?

Gianpiero Marconi¹ , Simona Masiero² , Lorenzo Raggi¹ , Gianni Barcaccia³ , Peggy Ozias-Akins⁴ , Mario Falcinelli¹ , Lucia Colombo² , Emidio Albertini¹

¹  Plant Biology, Agroenvironmental and Animal Biotechnology Department, University of Perugia, Italy

²  Department of Biology, University of Milano, Italy

³  Environmental Agronomy and Crop Science Department, University of Padova, Legnaro, Italy

⁴  Department of Horticulture and NESPAL, The University of Georgia, Tifton, GA

A fundamental contribution to the understanding of the genetic control of the apomictic pathway could be provided by a deep knowledge of molecular mechanisms that regulate the reproductive events. An mRNA profiling technique was applied to developmentally staged inflorescences of Poa pratensis and rsulted in 179 mRNA fragments differentially expressed between apomictic and sexual genotypes. In particular one of these genes, was termed APOSTART because of its START domain and its putative involvement in apomixis. START was named after the discovery of the StAR gene involved in human congenital lipoid adrenal hyperplasia which clinical phenotype includes the onset of profound adrenocortical insufficiency shortly after birth and male pseudohermaphroditism. Our results demonstrate that APOSTART is expressed exclusively in inflorescences of P. pratensis; no trascripts were detected in leaves or roots and we propose that the APOSTART is involved in sporogenesis and this is confirmed by its almost complete lack of expression in apomictic genotypes. ISH analysis revealed that APOSTART is expressed during both male and female meiosis in all micro- and megaspores. Strong signals were recorded up to the mature embryo sac stage. Overall, these data suggest that APOSTART may also be related to the programmed cell death that is involved in the non-functional megaspore and nucellar cell degeneration events that permit enlargement of maturing embryo sacs. Arabidopsis microarray data support this interpretation. Our current investigations for APOSTART in P. pratensis, other apomicts as well as in a meiotic mutant of Medicago falcate and in Arabidopsis, are reported and discussed.