Auxins are plant hormones that control growth and development, that is to say, they determine the size and structure of the plant. Among their many activities, auxins favor cell growth, root initiation, flowering, fruit setting and delay ripening.
At the molecular level, the hormone serves to unblock a transcription factor, a DNA-binding protein, which in turn activates or represses a specific group of genes. Some plants have more than 20 distinct auxin-regulated transcription factors. They are called ARFs (Auxin Response Factors) and control the expression of numerous plant genes in function of the task to be undertaken, that is to say, cell growth, flowering, root initiation, leaf growth etc.
This joint study, headed by Miquel Coll at the IRB and the IBMB-CSIC, has analyzed in detail the DNA binding mode used by various ARFs using X-ray diffraction techniques at the ALBA Synchrotron and at the European Synchrotron Radiation Facility (Grenoble, France). Researchers solved five 3D structures which have revealed why a given transcription factor is capable of activating a single set of genes, while other ARFs that are very similar with only slight differences trigger a distinct set.
Reference: "Structural basis for DNA binding specificity by the auxin-dependent ARF transcription factors" D. Roeland Boer, Alejandra Freire-Rios, Willy van den Berg, Terrens Saaki, Iain W. Manfield, Stefan Kepinski, Irene López-Vidrieo, Jose Manuel Franco, Sacco C. de Vries, Roberto Solano, Dolf Weijers, and Miquel Coll. Cell (2014).
IRB link: http://www.irbbarcelona.org/index.php/en/news/irb-news/scientific/scientists-discover-a-molecular-mechanism-that-controls-plant-growth-and-development
Atomic structure of an ARF/DNA complex. Auxins control the growth and development of plants through ARF (Author: R. Boer, IRB/CSIC)
