Molecular characterization and expression analysis of an apomixis-linked EXS gene in sexual and apomictic Paspalum notatum

PODIO M; DELGADO L; PESSINO SC; PUPILLI F; ORTIZ JPA

Foz de Iguazú

Congreso; 11th International Congress Plant Molecular Biology 2015 (IPMB 2015); 2015

International Plant Molecular Biology

A sequence homologous to the EXS (ERD/XPS/SPX) domain was found in the apomixis-linked BAC clone 346H10 of Paspalum simplex. EXS function in plants is still unknown, but a truncated form of this domain had been associated with proliferation in otherwise arrested cells in yeast, a function that resembles apospory. The objective of this work was to isolate and analyze the expression patterns of EXS genes in apomictic and sexual genotypes of P. notatum. A conserved 2,290-bp gene fragment was amplified from genomic DNA of both sexual and apomictic tetraploid plants. Amplicons were almost identical and highly similar to the EXS C-terminus of Zea mays and Oryza sativa. Southern-blot hybridization detected at least four copies/alleles of EXS in the species. Analysis of RNAseq of apomictic and sexual flowers showed only one coding isotig in the sexual plant but at least two (one truncated) in the apomict plant. qRT-PCR analyses revealed that PnEXS was expressed during all stages of reproductive development. Non-significant differences between sexual and apomictic genotypes were detected. In situ hybridization assays in reproductive organs revealed spatial and chronological altered expression in apomictic and sexual flowers. At anthesis, PnEXS was strongly expressed in the nucellar tissue of the sexual genotype, but only in the border cells of the megagametophyte in the apomictic one. At meiosis, the sense probe hybridized close to the megaspore mother cell in the apomictic genotype, but not in the sexual. Results indicated that expression patterns of EXS differed between sexual and apomictic genotypes.