Cross-species functional diversity within the PIN auxin efflux protein family

• DOI: 10.7554/elife.31804
• Publication Date: 2017-10-24T12:00:17Z
• Authors: Devin Lee O'Connor; Samuel Elton; Fabrizio Ticchiar...; Mon Mandy Hsia; John P Vogel; Ottoline Leyser
• Keywords: 0301 basic medicine; 571; a. thaliana; QH301-705.5; Science; Arabidopsis; developmental biology; 03 medical and health sciences; Plant Growth Regulators; stem cells; polarity; Biology (General); Plant Proteins; 580; plant biology; 0303 health sciences; patterning; Indoleacetic Acids; Q; Genetic Complementation Test; R; evo-devo; Membrane Transport Proteins; Stem Cell Research; organ initiation; Mutation; Medicine; Stem Cell Research - Nonembryonic - Non-Human; <i>a. thaliana</i>; Biochemistry and Cell Biology; auxin; Biotechnology; Developmental Biology; Brachypodium

In Arabidopsis, development during flowering is coordinated by transport of the hormone auxin mediated by polar-localized PIN-FORMED1 (AtPIN1). However Arabidopsis has lost a PIN clade sister to AtPIN1, Sister-of-PIN1 (SoPIN1), which is conserved in flowering plants. We previously proposed that the AtPIN1 organ initiation and vein patterning functions are split between the SoPIN1 and PIN1 clades in grasses. Here we show that in the grass Brachypodium sopin1 mutants have organ initiation defects similar to Arabidopsis atpin1, while loss of PIN1 function in Brachypodium has little effect on organ initiation but alters stem growth. Heterologous expression of Brachypodium SoPIN1 and PIN1b in Arabidopsis provides further evidence of functional specificity. SoPIN1 but not PIN1b can mediate flower formation in null atpin1 mutants, although both can complement a missense allele. The behavior of SoPIN1 and PIN1b in Arabidopsis illustrates how membrane and tissue-level accumulation, transport activity, and interaction contribute to PIN functional specificity.