Leydon, A. | Search bioRxiv

bioRxiv2026

CONSERVATION AND DIVERGENCE WITHIN THE ARABIDOPSIS TPL/TPR COREPRESSOR FAMILY

The TOPLESS (TPL) and TOPLESS-RELATED (TPR1-TPR4) corepressors, collectively the Arabidopsis TPX family, are recruited by client proteins to regulate nearly every major plant regulatory program. Here, we dissect the conservation and divergence between paralogs using a combination of higher-order genetics, transcriptomics, and a synthetic repression assay. TPL, TPR1, and TPR4 were found to act as the primary repressors for many pathways, while TPR2 and TPR3 played a lesser or sometimes opposite regulatory role. Natural variation in the EAR-binding pocket subdivided the family into three subtypes: TPL/TPR1, TPR2/TPR3 and TPR4, and this variation at least partially explained observed differences between mutant phenotypes. In addition, cell-type-specific expression of EAR-containing effectors were used to tune root architecture, providing a possible route to engineering other TPX-regulated pathways. These results suggest a model where the TPX family balances robustness under stable conditions with the need for flexibility during cell fate transitions or stress responses.

plant biology↗

bioRxiv2017

Synthetic hormone-responsive transcription factors can monitor and re-program plant development

Developmental programs continuously sculpt plant morphology to meet environmental challenges, and these same programs have been manipulated to increase agricultural productivity1,2. Small molecule phytohormones act as signals within these programs creating chemical circuitry3 that, in many cases, has been represented in mathematical models4,5. To date, model validation and forward engineering of plant morphology has been largely restricted to adding or subtracting genes, as more nuanced tools to modulate key control parameters identified by such models in vivo are severely limited6,7. Here, we use Arabidopsis thaliana to validate a novel set of synthetic and modular hormone activated Cas9-based repressors (HACRs) that respond to three phytohormones: auxin, gibberellins and jasmonates. We demonstrate that HACRs can regulate genes in response to both exogenous hormone treatments, as well as in response to local differences in endogenous hormone levels associated with developmental events. We further show that HACRs can be used to reprogram the agriculturally relevant traits of shoot branching and phyllotaxy by tuning canalization strength, a critical control parameter predicted by mathematical models. By deploying a HACR to re-parameterize the threshold for induction of the auxin transporter PIN-FORMED1 (PIN1), we observed a decrease in shoot branching and phyllotactic noise as predicted by existing models4,5. The approach described here provides a framework for improved mapping of developmental circuitry, as well as a means to better leverage model predictions to engineer development.

plant biology↗