Strigolactones Play an Important Role in Shaping Exodermal Morphology via a KAI2-Dependent Pathway

We report on factors regulating the hypodermal passage cells number in Petunia roots

Guowei Liu; Marina Stirnemann; Christian G├╝beli; Susanne Egloff; Pierre-Emmanuel Courty; Sylvain Aubry; Michiel Vandenbussche; Patrice Morel; Didier Reinhardt; Enrico Martinoia; Lorenzo Borghi

2019

Scholarcy highlights

  • Many plant roots possess two barrier layers, the exodermis and endodermis
  • A protocol based on fluorol yellow, previously used for endodermal passage cell quantification in Arabidopsis, could not be applied because of hypodermal auto-fluorescence in Petunia
  • The fact that hypodermal passage cells density was fully restored in dad1 and pdr1 mutants by the addition of rac-GR24, a synthetic SL analogue, shows that HPC presence is stimulated by SL
  • A similar arbuscular mycorrhizal-defective mutant phenotype was recently shown in rice kai2 mutants. These results suggest that HPC density might rely on a KARRIKIN INSENSITIVE 2/MAX2-dependent signaling pathway
  • The fact that the SL analogue GR24 only acted in its 5DS form and that this effect disappeared in kai2a mutants indicates that a bona fide receptor system mediates the SL-dependent promotion of HPC presence, and based on our data, we propose that it involves KAI2a/MAX2A
  • We show here that Petunia plants with high expression levels of DAD1, either in dad2 loss-of-function mutants or DAD1 OE lines, have increased HPC density compared with WT
  • A mutation in the Petunia karrikin sensor KARRIKIN INSENSITIVE 2 exhibits drastically decreased hypodermal passage cells amounts, supporting the hypothesis that the dimeric KAI2/MAX2 receptor is central in determining the HPC number

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