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

Polar localized PIN FORMED (PIN) efflux carriers proteins organize directional auxin flow and accumulation. Most flowering plants have  another family of PIN proteins called Sister of PIN1 (SoPIN1), which Arabidopsis and members of the Brassicacea family do not have. The grass Brachypodium dystachion has one SoPIN1 gene and two PIN1 genes: PIN1a and PIN1b. O´Connor and collaborators created CRISPR mutants in B. dystachion to study the function of these genes. The SoPIN1 mutant showed severe defects, similar to Arabidopsis pin1 mutant. By contrast the Brachypodium pin1a and pin1b mutants showed no clear organ defects. Heterologous expression of SoPIN1 partially complemented the Arabidopsis pin1-613 mutant; conversely, even though PIN1 was highly expressed and polar in the meristems it was not able to mediate organ initiations; showing a clear different function independent of transcriptional control. (Summary by Cecelia Vasquez-Robinet) eLife 10.7554/eLife.31804