A role for more axillary growth1 (MAX1) in evolutionary diversity in strigolactone signaling upstream of MAX2

Richard J Challis, Jo Hepworth, Céline Mouchel, Richard Waites, Ottoline Leyser

Research output: Contribution to journalArticlepeer-review


Strigolactones (SLs) are carotenoid-derived phytohormones with diverse roles. They are secreted from roots as attractants for arbuscular mycorrhizal fungi and have a wide range of endogenous functions such as regulation of root and shoot system architecture. To date, six genes associated with SL synthesis and signaling have been molecularly identified using shoot branching mutants of Arabidopsis (more axillary growth (max) mutants) and rice (dwarf (d) mutants). Here we present a phylogenetic analysis of the MAX/D genes to clarify the relationships of each gene with its wider family and to allow the correlation of events in the evolution of the genes with the evolution of SL function. Our analysis suggests that the notion of a distinct SL pathway is inappropriate. Instead, there may be a diversity of SL-like compounds, the response to which requires a D14/D14like protein. This ancestral system could have been refined toward distinct ligand-specific pathways channeled through MAX2, the most downstream known component of SL signaling. MAX2 is tightly conserved among land plants and is more diverged from its nearest sister clade than any other SL-related gene, suggesting a pivotal role in the evolution of SL signaling. In contrast, the evidence suggests much greater flexibility upstream of MAX2. The MAX1 gene is a particularly strong candidate for contributing to diversification of inputs upstream of MAX2. Our functional analysis of the MAX1 family demonstrates the early origin of its catalytic function and both redundancy and functional diversification associated with its duplication in angiosperm lineages.
Original languageEnglish
Pages (from-to)1885-1902
Number of pages18
JournalPlant Physiology
Issue number4
Early online date19 Feb 2013
Publication statusPublished - Apr 2013


  • Amino Acid Sequence
  • Arabidopsis
  • Arabidopsis Proteins
  • Base Sequence
  • Carrier Proteins
  • Conserved Sequence
  • Evolution, Molecular
  • Genes, Plant
  • Lactones
  • Medicago
  • Molecular Sequence Data
  • Multigene Family
  • Phenotype
  • Phylogeny
  • Plant Leaves
  • Plants, Genetically Modified
  • Principal Component Analysis
  • Sequence Alignment
  • Sequence Homology, Nucleic Acid
  • Signal Transduction

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