Histone deacetylases regulate MORE AXILLARY BRANCHED 2-dependent germination of Arabidopsis thaliana.

Under specific conditions, the germination of Arabidopsis thaliana is dependent on the activation of the KARRIKIN INSENSITIVE 2 (KAI2) signalling pathway by the KAI2-dependent perception of karrikin (KAR) or the artificial strigolactone analogue rac-GR24. To regulate induction of germination, the KAI2 signalling pathway relies on MORE AXILLARY BRANCHED 2 (MAX2)-dependent ubiquitination and proteasomal degradation of the repressor protein SUPPRESSOR OF MAX2 1 (SMAX1). It is not yet known how degradation of SMAX1 proteins eventually results in the regulation of seed germination, but it has been hypothesized that SMAX1-LIKE (SMXL) generally function as transcriptional repressors through the recruitment of co-repressors TOPLESS (TPL) and TPL-related, which in turn interact with histone deacetylases (HDACs). Here we show the involvement of histone deacetylases HDA6, HDA9, HDA19, and HDT1 in MAX2-dependent germination of Arabidopsis, and more specifically, that HDA6 is required for the induction of DLK2 expression in response to rac-GR24 treatment.