Ectopic overexpression of <Emphasis Type="Italic">Arabidopsis AtmiR393a</Emphasis> gene changes auxin sensitivity and enhances salt resistance in tobacco

To characterize the biological function of microRNA miR393 in tobacco, AtmiR393a gene was isolated from Arabidopsis using PCR and fused downstream to CaMV 35S promoter to make a plant expression construct 35S::AtmiR393a. The resultant construct was then introduced into tobacco with Agrobacterium-mediated transformation. Transgenic tobacco lines ectopically overexpressing AtmiR393a were successfully obtained. Transgenic lines L1 (a weak line), L2 (a middle line), and L3 (a strong line) were confirmed using stem-loop RT-PCRs and used to characterize the function of miR393 in tobacco. The results showed that L1, L2, and L3 exhibited reduced plant size and root length related to the WT control. In addition, seedling growth was less sensitive to IAA treatment and NaCl stress in three transgenic lines than the non-transgenic WT control. Furthermore, L1, L2, and L3 showed reduced phototropism relative to WT. Therefore, the biological function of miR393 is conserved in tobacco, just like in Arabidopsis. It regulates plant growth and development as well as the responses to environmental cues by influencing auxin sensitivity.