PT  - JOURNAL ARTICLE
AU  - Devin Lee O’Connor
AU  - Samuel Elton
AU  - Fabrizio Ticchiarelli
AU  - Mon Mandy Hsia
AU  - John Vogel
AU  - Ottoline Leyser
TI  - Cross-species functional diversity within the PIN auxin efflux protein family
AID  - 10.1101/089854
DP  - 2017 Jan 01
TA  - bioRxiv
PG  - 089854
4099  - http://biorxiv.org/content/early/2017/09/13/089854.short
4100  - http://biorxiv.org/content/early/2017/09/13/089854.full
AB  - 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.