| Summary: | Sexuality and apomixis are interconnected plant reproductive routes possibly behaving as polyphenic traits under the influence of the environment. In the subtropical grass <i>Paspalum notatum</i>, one of the controllers of apospory, a main component of gametophytic apomixis reproduction, is <i>TRIMETHYLGUANOSINE SYNTHASE 1</i> (<i>TGS1</i>), a multifunctional gene previously associated with RNA cleavage regulation (including mRNA splicing as well as rRNA and miRNA processing), transcriptional modulation and the establishment of heterochromatin. In particular, the downregulation of <i>TGS1</i> induces a sexuality decline and the emergence of aposporous-like embryo sacs. The present work was aimed at identifying <i>TGS1</i> target RNAs expressed during reproductive development of <i>Paspalum notatum</i>. First, we mined available RNA databases originated from spikelets of sexual and apomictic plants, which naturally display a contrasting <i>TGS1</i> representation, to identify differentially expressed mRNA splice variants and miRNAs. Then, the role of <i>TGS1</i> in the generation of these particular molecules was investigated in antisense <i>tgs1</i> sexual lines. We found that <i>CHLOROPHYLL A-B BINDING PROTEIN 1B-21</i> (<i>LHC Ib-21</i>, a component of the chloroplast light harvesting complex), <i>QUI-GON JINN</i> (<i>QGJ</i>, encoding a MAP3K previously associated with apomixis) and miR2275 (a meiotic 24-nt phasi-RNAs producer) are directly or indirectly targeted by <i>TGS1</i>. Our results point to a coordinated control exercised by signal transduction and siRNA machineries to induce the transition from sexuality to apomixis.
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