SlmiR393 controls the auxin receptor homologous genes expression, and regulates sensitivity to auxin in tomato root growth

- Identification of the SlmiR393 and its target genes, SlTIR1a, SlTIR1b and SlAFB6 (auxin receptor homologue).
- We analyzed their expression patterns in different organs of tomato.
- SlmiR393-mediated cleavage of SlTIR1a, SlTIR1b and SlAFB6 transcripts were verified using 5′RLM-RACE assay.
- Over-expression of SlmiR393 confers auxin-resistance in tomato.
- Repression of putative target genes and auxin-responsive genes by over-expression of SlmiR393.

MicroRNAs (miRNAs), key posttranscriptional regulators of eukaryotic gene expression, regulate a wide variety of developmental and physiological processes in plant. Our understanding of miR393 regulatory function in tomato, however, is limited. In this study, we identified SlmiR393 from tomato (Solanum lycopersicum), and systematically investigated its regulatory function in auxin-mediated growth and development. Our results indicated that SlmiR393 is predominantly expressed in the stem and flower, and predicted to target three auxin receptor homologous genes mRNA, including SlTIR1a, SlTIR1b and SlAFB6. Accordingly, 5′RLM-RACE cleavage assay demonstrated SlmiR393-mediated cleavage of SlTIR1a, SlTIR1b and SlAFB6 transcripts in vivo. Moreover, transgenic tomato plants that constitutively expressed the SlmiR393 gene repressed expression of three auxin receptor homologue, and caused inhibition of primary root growth and hyposensitivity to auxin in root growth. Further analyses revealed that SlmiR393 over-expression alters the expression genes involved in auxin signal transduction. Take together, these data suggest that SlmiR393 functions in negative modulation of auxin response for plant growth and development of tomato.