KAI2 regulates seedling development by mediating light-induced remodelling of auxin transport

Maxime Hamon-Josse, José Antonio Villaécija-Aguilar, Karin Ljung, Ottoline Leyser, Caroline Gutjahr, Tom Bennett

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Photomorphogenic remodelling of seedling growth is a key developmental transition in the plant life cycle. The α/β-hydrolase signalling protein KARRIKIN-INSENSITIVE2 (KAI2), a close homologue of the strigolactone receptor DWARF14 (D14), is involved in this process, but it is unclear how the effects of KAI2 on development are mediated. Here, using a combination of physiological, pharmacological, genetic and imaging approaches in Arabidopsis thaliana (Heynh.) we show that kai2 phenotypes arise because of a failure to downregulate auxin transport from the seedling shoot apex towards the root system, rather than a failure to respond to light per se. We demonstrate that KAI2 controls the light-induced remodelling of the PIN-mediated auxin transport system in seedlings, promoting a reduction in PIN7 abundance in older tissues, and an increase of PIN1/PIN2 abundance in the root meristem. We show that removing PIN3, PIN4 and PIN7 from kai2 mutants, or pharmacological inhibition of auxin transport and synthesis, is sufficient to suppress most kai2 seedling phenotypes. We conclude that KAI2 regulates seedling morphogenesis by its effects on the auxin transport system. We propose that KAI2 is not required for the light-mediated changes in PIN gene expression but is required for the appropriate changes in PIN protein abundance within cells.

Original languageEnglish
Pages (from-to)126-140
Number of pages15
JournalNew Phytologist
Volume235
Issue number1
DOIs
StatePublished - Jul 2022

Keywords

  • Arabidopsis
  • KAI2 signalling
  • PIN proteins
  • auxin
  • auxin transport
  • light signalling
  • seedling development

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