Researchers led by Francesca Quattrocchio and Ronald Koes (Swammerdam Institute for Life Sciences) have discovered a gene encoding a transcription factor (PH3) that remained conserved during the evolution of very different families of plants, although it now controls different processes in different species. This study, about an interesting evolutionary mechanism that couples new target genes to ancient regulators, was published in The Plant Cell on March 14, 2016.
In petunia, the PH3 transcription factor controls the process of hyper-acidification of the vacuolar lumen in petal cells. A low pH is necessary to shift the colour of the pigments accumulated in the vacuoles of petal cells towards red. This is the colour of choice for a successful attraction of pollinators. Flowers of petunia plants that contain a non-functional PH3 gene are instead bluish due to a high vacuolar pH.
A similar protein (TTG2) in Arabidopsis regulates the development of hairs on the leaf surface (trichomes) and in the roots (root hairs). Expression of TTG2 in petunia plants where the PH3 gene is inactivated by mutations, restores vacuolar acidification and flower colour, demonstrating that in spite of the very different phenotype of the mutants in arabidopsis and petunia, the two proteins are totally interchangeable. The analysis of the physical localisation of genes (synteny) around PH3, TTG2 and homologues from other species, confirmed that these genes originate form one ancestor.
Walter Verweij, Cornelis E Spelt, Mattijs Bliek, Michel de Vries, Niek Wit, Marianna Faraco, Ronald Koes and Francesca M. Quattrocchio (2016) Functionally similar WRKY proteins regulate vacuolar acidification in petunia and hair development in Arabidopsis. The Plant Cell, Advance Publication March 14, 2016