RT Journal Article SR Electronic T1 bHLH heterodimer complex variations shape meristems in Arabidopsis thaliana by affecting target gene specificity JF bioRxiv FD Cold Spring Harbor Laboratory SP 2022.06.02.494582 DO 10.1101/2022.06.02.494582 A1 Eliana Mor A1 Markéta Pernisová A1 Max Minne A1 Guillaume Cerutti A1 Dagmar Ripper A1 Jonah Nolf A1 Jennifer Andres A1 Laura Ragni A1 Matias D. Zurbriggen A1 Bert De Rybel A1 Teva Vernoux YR 2022 UL http://biorxiv.org/content/early/2022/06/05/2022.06.02.494582.abstract AB The main regions of cell proliferation in plants are the root and shoot apical meristems during primary growth and the vascular cambia as lateral meristems during secondary thickening. A number of unique regulators have been described in each of these meristems, suggesting that these different meristems might have independently evolved dedicated transcriptional networks to balance cell proliferation. Here, we show that the basic Helix Loop Helix (bHLH) transcription factor complexes formed by TARGET OF MONOPTEROS5 (TMO5), LONESOME HIGHWAY (LHW) and their close homologs are broadly expressed throughout plant development and operate as general regulators of cell proliferation in all meristems. Yet, genetic and expression analyses indicate that these complexes have specific functions in distinct meristems mediated by heterodimer complex variations between members of the TMO5 and LHW subclades. We determine that this is primarily due to their expression domains limiting the possible combinations of heterodimer complexes within a certain meristem, and to a certain extent to the absence of some members in a given meristem. We further demonstrate target gene specificity for heterodimer complexes, suggesting that spatial differences in transcriptional responses through heterodimer diversification allow a common bHLH heterodimer complex module to contribute to the control of cell proliferation in multiple meristems.