A precise balance of TETRASPANIN1/TORNADO2 activity is required for vascular proliferation and ground tissue patterning in Arabidopsis

The molecular mechanisms guiding oriented cell divisions in the root vascular tissues of Arabidopsis thaliana are still poorly characterized. By overlapping bulk and single-cell transcriptomic datasets, we unveiled TETRASPANIN1 (TET1) as a putative regulator in this process. TET1 is expressed in root vascular cells and loss-of-function mutants contain fewer vascular cells files. We further generated and characterized a CRISPR deletion mutant and show, unlike previously described mutants, that the full knock out is additionally missing endodermal cells in a stochastic way. Finally, we show that HA-tagged versions of TET1 are functional in contrast to fluorescent TET1 translational fusions. Immunostaining using HA-TET1 lines complementing the mutant phenotype suggested a dual plasma membrane and intracellular localization in the root vasculature and a polar membrane localization in young cortex, endodermal and initial cells. Taken together, we show that TET1 is involved in both vascular proliferation and ground tissue patterning. Our initial results pave the way for future work into deciphering its precise mode of action. Arabidopsis seedlings of the pRPS5A::DOF2.1-GR line were grown on control plates and transferred to plates suppemented with 10uM DEX for the indicated times to induce the DOF2.1 transcription factor. Root meristems were harvested and RNA extraction was performed before RNA sequencing.