Strigolactones are needed for miR156 inducibility by drought in tomato

Strigolactones (SL) are terpenoid hormones influencing many aspects of plant development, biotic interactions and responses to environmental stress, namely drought. MicroRNAs (miRNAs) are a set of small, non-protein-coding RNAs that regulate gene expression at the post-transcriptional level. Given the inducibility of certain miRNAs by environmental stress, and the pervasive effects of SL on plant acclimatization to drought, we asked whether the latter may have a role in miRNA metabolism in such conditions in tomato. The results show that SL synthesis in the shoot, but not in the root, is needed for the accumulation of miR156 (but not miR166) in both organs under drought. A preliminary analysis of pre-miR156 levels indicates that stress triggers precursor accumulation only in shoots, which implies that mature miR156 moves rootwardly under drought. Additionally, pre-miRNA inducibility by drought seems to be only marginally affected by SL availability, suggesting that the latter may rather play their role later in miRNA maturation - a process whose efficiency towards specific miRNAs is sensitive to cellular context.