Expression of lorelei-like genes in aposporous and sexual Paspalum notatum plants
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Gametophytic apomictic plants form non-reduced embryo sacs that generate clonal embryos by parthenogenesis, in the absence of both meiosis and egg-cell fertilization. Here we report the sequence and expression analysis of a lorelei-like Paspalum notatum gene, n20gap-1, which encodes a GPI-anchored protein previously associated with apomixis in this species. Phylogeny trees showed that n20gap-1 was evolutionary related to the Arabidopsis thaliana lorelei genes At4g26466 and At5g56170. The lorelei At4g26466 disruption was shown to be detrimental to sperm cell release in arabidopsis. RFLP (Restriction Fragment Length Polymorphism) analysis revealed the occurrence of several homologous sequences in the Paspalum notatum genome, exhibiting polymorphisms genetically linked to apomixis. Real-time PCR showed that lorelei-family genes present a minor activity peak at pre-meiosis and a major one at anthesis. The apomictic genotype analyzed showed a significantly increased activity at pre-meiosis, post-meiosis and anthesis with respect to a sexual genotype. In situ hybridization assays revealed expression in integuments, nucellus and the egg-cell apparatus. Several n20gap-1 alleles differing mainly at the 3′ UTR sequence were identified. Allele-specific real-time PCR experiments showed that allele 28 was significantly induced in reproductive tissues of the apomictic genotype with respect to the sexual genotype at anthesis. Our results indicate that P. notatum lorelei-like genes are differentially expressed in representative sexual (Q4188) and apomictic (Q4117) genotypes, and might play a role in the final stages of the apomixis developmental cascade. However, the association of n20gap-1 expression with the trait should be confirmed in significant number of sexual and apomictic genotypes.
KeywordsApomixis Apospory Lorelei Paspalum notatum Plant reproduction
Thanks are due to Prof. Camilo Quarin for kindly providing the plant material used in this work. We thank Dr. Michael Hayward, Dr. Peggy Ozias-Akins and Dr. Marta Bianchi for valuable corrections and suggestions that helped to improve the manuscript. This work was funded by Agencia Nacional de Promoción Científica y Tecnológica, Argentina (ANPCyT PICT 2003 13578, PICT 2007 00476 and PME 2006 03083); Consejo Nacional de Investigaciones Científicas y Técnicas Argentina (CONICET, PIP 2008 6805); Centro Argentino Brasileño de Biotecnología (CABBIO Proy. 2004 012). Podio M, Laspina N and Siena L received a fellowship from CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina). Felitti SA, Seijo JG., González AM, Ortiz JPA and Pessino SC are career members of CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina).
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