Transcriptional diversification and functional conservation between DELLA proteins in Arabidopsis

[EN] Plasticity and robustness of signaling pathways partly rely on genetic redundancy, although the precise mechanism that provides functional specificity to the different redundant elements in a given process is often unknown. In Arabidopsis, functional redundancy in gibberellin signaling has been largely attributed to the presence of five members of the DELLA family of transcriptional regulators. Here, we demonstrate that two evolutionarily and functionally divergent DELLA proteins, RGL2 and RGA, can perform exchangeable functions when they are expressed under control of the reciprocal promoter. Furthermore, both DELLA proteins display equivalent abilities to interact with PIF4 and with other bHLH transcription factors with a reported role in the control of cell growth and seed germination. Therefore, we propose that functional diversification of Arabidopsis DELLA proteins has largely relied on changes in their gene expression patterns rather than on their ability to interact with different regulatory partners, model also supported by a clustering analysis of DELLA transcript profiles over a range of organs and growth conditions that revealed specific patterns of expression for each of these genes. We deeply appreciate the help of Marta Trenor and Laura Garcia-Carcel in the initial stages of this work. We also thank Tai-ping Sun (Duke University) and the Arabidpsis Biological Resource Center for seeds, Marta Boter for the pGBKT7 and pGADT7 Gateway vectors, Santiago Elena (IBMCP, CSIC-UPV) for useful comments on the manuscript, and Francois Parcy (IRTSV, CNRS-CEA) for fruitful discussions and hosting MAB. Work in the authors' laboratories is funded by grants BIO2007-60923 and BIO2005-07284 from the Spanish Ministry of Science and Innovation. J.G.B. is the recipient of a CSIC I3P Fellowship and J.A.M. is the recipient of a Fellowship from the Fundacion "la Caixa. Gallego-Bartolome, J.; Minguet, E.; Marin, JA.; Prat, S.; Blazquez Rodriguez, MA.; Alabadí Diego, D. (2010). Transcriptional diversification and functional conservation between DELLA proteins in Arabidopsis. Molecular Biology and Evolution. 27(6):1247-1256. https://doi.org/10.1093/molbev/msq012