Paralogous radiations of PIN proteins with multiple origins of noncanonical PIN structure

Tom Bennett, Samuel F. Brockington, Carl Rothfels, Sean W. Graham, Dennis Stevenson, Toni Kutchan, Megan Rolf, Philip Thomas, Gane Ka Shu Wong, Ottoline Leyser, Beverley J. Glover, C. Jill Harrison

Research output: Contribution to journalArticlepeer-review

104 Scopus citations


The plant hormone auxin is a conserved regulator of development which has been implicated in the generation of morphological novelty. PIN-FORMED1 (PIN) auxin efflux carriers are central to auxin function by regulating its distribution. PIN family members have divergent structures and cellular localizations, but the origin and evolutionary significance of this variation is unresolved. To characterize PIN family evolution, we have undertaken phylogenetic and structural analyses with a massive increase in taxon sampling over previous studies. Our phylogeny shows that following the divergence of the bryophyte and lycophyte lineages, two deep duplication events gave rise to three distinct lineages of PIN proteins in euphyllophytes. Subsequent independent radiations within each of these lineages were taxonomically asymmetric, giving rise to at least 21 clades of PIN proteins, of which 15 are revealed here for the first time. Although most PIN protein clades share a conserved canonical structure with a modular central loop domain, a small number of noncanonical clades dispersed across the phylogeny have highly divergent protein structure. We propose that PIN proteins underwent sub- and neofunctionalization with substantial modification to protein structure throughout plant evolution. Our results have important implications for plant evolution as they suggest that structurally divergent PIN proteins that arose in paralogous radiations contributed to the convergent evolution of organ systems in different land plant lineages.

Original languageEnglish
Pages (from-to)2042-2060
Number of pages19
JournalMolecular biology and evolution
Issue number8
StatePublished - Aug 2014


  • PIN protein
  • auxin
  • auxin transport
  • phylogeny
  • plant evolution
  • protein structure


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