Complete loss of A-ARF activity in bryophytes reveals a role for auxin-adjacent regulatory networks

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Bascom C Jr, Tu D, Repakula S, Prigge MJ, Estelle M. 2025. The role of auxin-mediated gene activation in the bryophyte, Physcomitrium patens. Journal of Experimental Botany 76, https://doi.org/10.1093/jxb/eraf183

Researchers have recently generated a septuple A-class AUXIN RESPONSE FACTOR (A-ARF) mutant, nullifying all A-ARF function in the moss Physcomitrium patens (Bascom et al., 2025). Septuple mutants (Pparfa^sept) are unable to induce gene expression in response to exogenous auxin, allowing dissection of auxin-mediated developmental transitions and unmasking auxin-independent gene regulation. The Pparfa^sept plants reveal how constitutive auxin signalling repression is not equivalent to loss of auxin-mediated gene induction. This simple premise lends credence to the idea that auxin acts as a facilitator in conjunction with other auxin-independent transcription factors to regulate development processes in land plants.