ATP-Competitive mTOR Kinase Inhibitors Delay Plant Growth by Triggering Early Differentiation of Meristematic Cells Without Developmental Patterning Change

The study investigated the effects of ATP-competitive mTOR kinase inhibitors, referred to as asTORis, on the growth of Arabidopsis thaliana, a model plant organism. It was found that asTORis inhibited root growth in a dose-dependent manner, with first- and second-generation inhibitors having 50% growth inhibitory doses (GI50) of less than 10 μM and less than 1 μM, respectively. These values were similar to those observed in mammalian cells. The inhibitors specifically reduced the length of the meristematic zone, the division zone within it, epidermal cells in the elongation zone, and root hair cells. While these treatments led to early differentiation of meristematic cells, they did not alter the overall pattern of cell differentiation. The study also confirmed that the root hair growth phenotype was specific to asTORis, as it was not replicated by other growth inhibitors. The effects of asTORis were consistent across various flowering plants, suggesting their potential use in studying the TOR pathway in a wide range of angiosperms, including crops.