Dissecting the putative role of RNA methyltransferases in apomixis

LEBLANC O; SIENA L; ORTIZ JPA; PESSINO SC

Foz de Iguazú

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

International Plant Molecular Biology

Seed formation in Angiosperms initiates within the female gametophyte after the central cell and the egg cell are fertilized by a sperm cell, producing the endosperm and the embryo, respectively. This double fertilization event, typical of plant sexual reproduction, is bypassed during gametophytic apomixis, an alternative mode of reproduction in which unreduced egg cells develop autonomously giving rise to viable seeds harboring maternal embryos. Despite significant progress in the field achieved in both apomictic and sexual model species, complete molecular decoding of apomictic reproduction still is lacking. Using comparative approaches, candidate genes have been identified in Paspalum notatum, a tropical forrage reproducing through aposporous apomixis. Several of these candidates were assigned with functions in both transcriptional regulation and RNA post-transcriptional adenosine and guanosine methylation, a modification critical for stability, processing, editing and splicing. These enzymes, which functional characterization was achieved in non plant model systems mainly play critical roles in diverse developmental processes, including meiosis and embryogenesis. One P. notatum candidates that was found downregulated in apomicts encodes TRIMETHYLGUANOSINE SYNTHASE1 protein (TGS1), a S-adenosyl-L-methionine (S-AdoMet)-dependent methyltransferase involved in both formation of sn/snoRNAs caps and PPAR-mediated transcriptional activation. To better understand TGS1 function during sexual plant reproduction and explore its role during the transition from sexual reproduction to apomixis, we initiated the functional characterization of A. thaliana mutants showing defects in reproduction and the mining of Paspalum transcriptomes to investigate differences in transcript processing.