Molecular features of aposporous apomixis in Paspalum notatum

PESSINO SC

Saint Louis, Missouri

Congreso; 9th IPMB Congress; 2009

International Society for Plant Molecular Biology

Paspalum notatum is a subtropical perennial grass including diploid sexual and tetraploid apomictic cytotypes. In the species apospory is inherited as a single dominant factor with a distorted segregation ratio. Complete genetic maps were developed at the diploid (sexual) and tetraploid (apomictic) level. The apospory-specific controlling region (ASGR) consisted of a single area of around 36 Mbp, displaying strong restriction of recombination. It showed preferential chromosome pairing with one of the homologues and partial synteny to rice chromosomes 2 and 12. Sequence characterization and extension by chromosomal walking of markers completely linked to the apospory locus showed the region is plagued with non-coding sequences and retrotransposons. Inflorescences differential expresion analysis revealed 65 unigenes specifically activated or repressed at the onset of aposporous development. They included 45 protein-coding genes organized within a few ontology categories (signal transduction, transcription, protein turnover, cell cycle) and 20 non-coding transcripts showing homology with miRNAs and retrotransposons, which might be playing a regulatory role in aposporous development. Functional annotation and co-expression data originated from arabidopsis orthologues allowed prediction of the molecular networks integrated by these particular genes In situ hybridization on reproductive tissues confirmed a strong differential expression in ovules (and sometimes also in anthers) for most of the analyzed candidates. A biolistic transformation platform and vectors were developed for the future production of transgenic plants overexpressing or repressing the candidate genes. Molecular and cytoembryological analysis of these transformants will contribute to elucidate the molecular pathways involved in apospory.