Cloning a somatic embryogenesis like-kinase (serk) gene of Paspalum notatum

PODIO M; FELITTI, S; SIENA LA; ORTIZ, JPA

Buenos Aires

Simposio; The 6th International Symposium of the molecular breeding of forage and turf; 2010

Molecular Breeding of Forage and Turf International Committee

Paspalum notatum is a rhizornatous species widely distributed in native grasslands from central Mexico to Argentina. Different ploidy levels were reported for this species. Sexual diploids are cross-pollinated due to self-incompatibility, while the tetraploid races reproduce by obligate aposporous apomixis. This type of reproduction involves the formation of unreduced megagarnetophytes from nucellar cells, and the development of the embryo by parthenogenesis. Endosperm formation requires the fertilization of the two polar nuclei (pseudogarny). Apomixis results in progenies that are genetically exact copies of the female plant. The SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (serk) gene plays a fundamental role in somatic embryogenesis of several angiosperms and was associated with apomixis in Poa Pratensis. It was proposed that Ppserk activation in nucellar cells of apomictic genotypes of P. pratensis is the switch that channels embryo sac development, and could redirect signaling gene products to compartments other than their typical ones (somatic cells instead of a megaspore mother cell). The objective of this work was to isolate and characterize the gene serk from tetraploid P. notatum. Oligonucleotides were designed based on conserved regions of serk genomic sequences of P. pratensis, rice and maize. A fragment of 200 bp was amplified from genotypes Q4188 (sexual) and Q4l17 (apomictic). A chromosome walking strategy was used for extending Pnserk from six non-cloned genomic libraries. Afragment of 711 bp containing homologous sequences to the exons 9 and 10 of Ppserk and the intronic flanking sequences were isolated. Southern-blot hybridization indicated the presence of at least four copies of Pnserk in tetraploid genotype Q4117. Further extension experiments will allow the isolation of the complete genomic and cDNA sequences of Pnserk in order to functionally characterize this gene in the species