Mixing and matching SMXL proteins to fine-tune strigolactone responses

A common mechanism in plant hormone signaling is hormonedependent degradation of downstream repressors.In the case of strigolactone(SL)signaling,one group of SUPPRESSOR OF MORE AXILLARY BRANCHES 2(MAX2)1-LIKE(SMXL)proteins undergoes hormone-dependent degradation,while another does not.A recent publication in Molecular Plant by Li et al.(2024)illustrates that mixing and matching a SMXL resistant to SL degradation with a SMXL sensitive to SL degradation finely tunes SL responses.This phenomenon could reflect a naturally occurring negative transdominance,which is a dominantnegative effect arising not from a mutant allele of the same gene but rather from a different gene altogether(Veitia,2007).This trans-acting protein attenuates SL-dependent degradation of the SMXL complex.These findings have exciting implications for how different SMXL combinations could result in a gradient of SL responses.