A GPI-anchored protein down-regulated in inflorescences of aposporous Paspalum notatum is the ortholog to the Arabidopsis thaliana LORELEI genes

FELITTI S; SEIJO G; GONZÁLEZ AM; PODIO M; LASPINA N; ORTIZ JPA; PESSINO SC

Buenos Aires

Simposio; The 6th International Symposium of the Molecular Breeding of Forage and Turf; 2010

Molecular Breeding of Forage and Turf International Committee

Apomixis is an asexual mode of reproduction representing an important potential technology for agriculture. Gametophytic apomictic plants form non-reduced embryo sacs that generate clonal embryos by parthenogenesis, in the absence of egg cell fertilization. In a recent work, our group identified 65 genes differentially expressed in immature inflorescences of apomictic and sexual Paspalum notatum plants. Here we present the full-sequence and expression characterization for one of these candidates, N20gap, a gene homologous to GPI-anchored proteins. N20gap was shown to be genetically linked to the P. notatum apospory-specific genomic region and up-regulated in inflorescences of sexual plants with respect to apomictic ones. Rapid amplification of cDNA ends (RACE) experiments allowed extension and characterization of the N20gap full cDNA sequence, revealing the existence of several alleles/gene members which are expressed in inflorescences. The structure of the N20GAP protein and its physicochemical properties were predicted by in silico analysis. Genomic southern blotting confirmed the presence of several alleles and/or gene copies, and displayed polymorphisms genetically linked to the reproductive mode. Comparative RNA in situ hybridization experiments on immature inflorescences showed N20gap expression down-regulation in ovules and pollen mother cells of the aposporous genotype. Blastx searches revealed that the N20gap is highly homologous to the four Arabidopsis thaliana LORELEI genes (At5g56170, At2g20700, At4g26466 and At4g28280), whose silencing was shown to be detrimental to sperm cell release in this species. Down-regulation of the N20gap expression might be impairing egg cell fertilization in P. notatum non-reduced embryo sacs. Transforming P. notatum sexual plants with constructs promoting N20gap silencing would help to elucidate if the derived phenotype in this species is actually reminiscent of the LORELEI one or if the silencing of the orthologs to At5g56170 and At2g20700 could be causing an alternative phenotype in P. notatum. Hairpin and antisense vector constructions and a methodology to transform Paspalum are being developed in our laboratory in order to perform these experiments.