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SUPPRESSOR OF MAX2 1-LIKE (SMXL) homologs are MAX2-dependent repressors of Physcomitrium patens growth. SUPPRESSOR OF MAX2 1-LIKE (SMXL) homologs are MAX2-dependent repressors of Physcomitrium patens growth: SMXL proteins repress moss growth through a conserved ancestral signaling pathway
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Edité par CCSD ; American Society of Plant Biologists (ASPB) -
International audience. SUPPRESSOR OF MAX2 (SMAX)1-LIKE (SMXL) proteins are a plant-specific clade of type I HSP100/Clp-ATPases. SMXL genesare present in virtually all land plant genomes. However, they have mainly been studied in angiosperms. In Arabidopsis(Arabidopsis thaliana), 3 functional SMXL subclades have been identified: SMAX1/SMXL2, SMXL345, and SMXL678. Of these,2 subclades ensure endogenous phytohormone signal transduction. SMAX1/SMXL2 proteins are involved in KAI2 ligand (KL)signaling, while SMXL678 proteins are involved in strigolactone (SL) signaling. Many questions remain regarding the mode ofaction of these proteins, as well as their ancestral roles. We addressed these questions by investigating the functions of the 4SMXL genes in the moss Physcomitrium patens. We demonstrate that PpSMXL proteins are involved in the conserved ancestralMAX2-dependent KL signaling pathway and negatively regulate growth. However, PpSMXL proteins expressed in Arabidopsiscannot replace SMAX1 or SMXL2 function in KL signaling, whereas they can functionally replace SMXL4 and SMXL5 and restore root growth. Therefore, the molecular functions of SMXL proteins are conserved, but their interaction networks are not.Moreover, the PpSMXLC/D clade positively regulates SL signal transduction in P. patens. Overall, our data reveal that SMXLproteins in moss mediate crosstalk between the SL and KL signaling pathways.
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