Abstract:In order to understand the function of SlmiR393 in tomato (Lycopersicum esculentum), the precursor sequences and potential target genes of SlmiR393 were obtained by searching tomato genome database with computational algorithms. The SlmiR393 gene was amplified from tomato genomic DNA by PCR and integrated into plant expression vector pLP35s-100. Sly-miR393 guided-cleavage to putative target genes mRNAs was validated using 5' RACE RT-PCR. The expression of SlmiR393 and its target genes in tomato different tissues were determined by Real-time quantitative PCR. The results showed that the precursor sequence of SlmiR393 contains the complete hairpin structure. Three auxin receptor gene homologs (SlTIR1, SlTIR1-like1 and SlAFB) mRNAs contain recognition sites with high complementarities to Sly-miR393 sequence. In tomato, SlmiR393 directs the cleavage of SlTIR1, SlTIR1-like1 and SlAFB mRNA. The expression of SlmiR393 has opposite effects on SlTIR1, SlTIR1-like1 and SlAFB in stem, leaf, bud and flower, respectively. Therefore, it was suggested that SlmiR393 might direct specific target gene mRNA cleavage in tomato specific tissue and developmental stage, and the auxin receptor homologous (SlTIR1, SlTIR1-like1 and SlAFB) were validated to be as target of SlmiR393. Additionally, the pLP35s-pre-SlmiR393 vector containing SlmiR393 gene was successfully constructed with CaMV 35S as promoter, which laid a foundation for further studies of SlmiR393 function in auxin signaling pathway in tomato.