CONICET | Buscador de Institutos y Recursos Humanos

In Angiospserms, apomixis refers to asexual reproduction through seeds. Recently, the association between the deregulation of genes encoding RNA methyltransferases and apomictic development in Paspalum notatum was reported. TGS1-like is a plant specific homolog of TGS1 (trimethyl guanosylsynthase-1) whose expression is positively correlated with the rate of sexuality in facultative apomictic P. notatum genoytpes. TGS1 performs a dual activity in yeast, mammals and insects. First, it trimethylates the 5' end of sn(o)RNAs involved in splicing, rRNA processing and telomerase function. TGS1 also can act as a transcription co-activator associated with PRIP. The objective of this work is to characterize TGS1-like function in the Arabidopsis thaliana plant model. RT-PCR revealed an over-expression of TGS1-like in reproductive tissues. Transgenic plants carrying synthetic reporter constructs (pTGS1-like:TGS1-like:GUS/GFP) showed expression in sub-terminal root tips, lateral root meristems, stomatas, ovule primordia, undifferentiated male and female gametophytes, egg cells and embryos. Homozygous plants for tgs1-like mutant alleles showed reduced fertility (up to 60% of aborted seeds) and segregation analyses of tgs1-like mutations through both sexes indicated gametophytic effects. Cytoembryological analysis of tgs1-like plants revealed defects during megagametogenesis and embryo development. Using cell-identity markers we further observed cell fate alterations during both female gametogenesis and early seed development. In particular, monitoring the expression of auxin response reporter genes transmitted paternally in early tgs1-like/+ embryos revealed abnormal patterns. The knowledge gained from this work indicates an essential role for TGS1-like in cell fate specification during sexual female gametogenesis and in embryo patterning.