CONICET | Buscador de Institutos y Recursos Humanos

Apospory is an apomictic (asexual) reproductive pathway characterized by the occurrence of multiple non-reduced embryo sacs in plant ovules. In prior differential display analyses we identified a transcript encoding a MEKK (mitogen-activated protein kinase kinase kinase)-like protein (PNMEKK1), which showed differential expression in floral tissues of sexual and apomictic Paspalum notatum biotypes. The objective of the study reported here was to characterize PNMEKK1 transcripts expressed in the flower in terms of sequence, expression, genome position and function. RNAseq analysis using long-read Roche 454 sequencing showed 1 and 4 alleles/paralogs in sexual and aposporous plants, respectively. Real-time PCR and in situ hybridization analyses revealed both chronological and spatial differential expression in reproductive tissues of sexual and apomictic genotypes. Interestingly, coding strands were upregulated at late premeiosis/meiosis in the nucellus of aposporous plants. Two independent transformation events of an obligate aposporous plant with a PNMEKK1 hairpin construction showed a significant drop in both the expression of the candidate gene and the occurrence of aposporous embryo sacs (AES). Mapping analysis revealed that PNMEKK1 segregated independently from apospory. However, a long non-coding RNA transcript with similarity to PNMEKK1 and retroelements mapped within the Paspalum notatum apospory-controlling region and showed expression only in the aposporous genotype. Our results indicate that PNMEKK1 activity is necessary to promote AES formation and suggest it might be modulated by long non-coding RNAs originated from the apospory-controlling region.