Characterization of the molecular basis of aposporous apomixis in Paspalum notatum

PESSINO S

Rosario

Congreso; XV Congreso Latinoamericano de Genética; 2012

Sociedad Argentina de Genética

Paspalum notatum is a subtropical grass including diploid sexual and tetraploid aposporous apomictic races. Several fully sexual tetraploids were artificially created. A pseudo-testcross population was used to produce a genetic map at the tetraploid level. The apospory-controlling region (ACR) consisted of a single non-recombinant block of about 36 Mbp mapping onto linkage group P17a, which displayed macrosynteny to rice chromosomes 2 and 12. Pollen viability and male meiosis analysis indicated that apomixis could be associated with large genome rearrangements. A list of 65 candidates differentially expressed in reproductive tissues of apomictic and sexual plants was produced. Main pathways affected were signal transduction, DNA, RNA and protein metabolism, cell cycle, transcription regulation and transport. Several gypsy retrotransposons, some of them carrying transduplicated segments of genes previously associated with apomixis (serk, cytP450) were included among the differentially expressed transcripts. Besides, molecular analyses showed that immediately after autopolyploidization, the Paspalum genome suffers genetic, epigenetic and transcriptional modifications. No evidence was found that the DNA repair system was involved in the genetic changes. Instead, they could have originated from insertion of retrotransposons into pseudogenes. A biolistic plant transformation protocol is currently being used to produce transformants with a modified expression of the candidates positionally and/or transcriptionally associated with apomixis.