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Title: Functional profiling identifies genes involved in organ specific branches of the PIF3 regulatory network in Arabidopsis

Author
item SENTANDREU, MARIA - Institute De Recerca I Tecnologia Agroalimentaries (IRTA)
item MARTIN, GUIOMAR - Institute De Recerca I Tecnologia Agroalimentaries (IRTA)
item GONZALEZ-SCHAIN, NAHUEL - Institute De Recerca I Tecnologia Agroalimentaries (IRTA)
item LEVIAR, PABLO - Institute De Recerca I Tecnologia Agroalimentaries (IRTA)
item SOY, JUDIT - Institute De Recerca I Tecnologia Agroalimentaries (IRTA)
item TEPPERMAN, JAMES - US Department Of Agriculture (USDA)
item QUAIL, PETER - US Department Of Agriculture (USDA)
item MONTE, ELANA - Institute De Recerca I Tecnologia Agroalimentaries (IRTA)

Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2011
Publication Date: 11/23/2011
Citation: Sentandreu, M., Martin, G., Gonzalez-Schain, N., Leviar, P., Soy, J., Tepperman, J.M., Quail, P.H., Monte, E. 2011. Functional profiling identifies genes involved in organ specific branches of the PIF3 regulatory network in Arabidopsis. The Plant Cell. 23:3974-3991.

Interpretive Summary: This paper identifies four genes that act in darkness to regulate different facets of the growth and development of post-germinative seedlings before they emerge into light. These results define branches in the regulatory network that controls early seedling behavior both before and after first exposure to light.

Technical Abstract: The phytochrome (phy)-interacting basic helix-loop-helix transcription factors (PIFs) constitutively sustain the etiolated state of dark-germinated seedlings by actively repressing deetiolation in darkness. This action is rapidly reversed upon light exposure by phy-induced proteolytic degradation of the PIFs. Here, we combined a microarray-based approach with a functional profiling strategy and identified four PIF3-regulated genes misexpressed in the dark (MIDAs) that are novel regulators of seedling deetiolation. We provide evidence that each one of these four MIDA genes regulates a specific facet of etiolation (hook maintenance, cotyledon appression, or hypocotyl elongation), indicating that there is branching in the signaling that PIF3 relays. Furthermore, combining inferred MIDA gene function from mutant analyses with their expression profiles in response to light-induced degradation of PIF3 provides evidence consistent with a model where the action of the PIF3/MIDA regulatory network enables an initial fast response to the light and subsequently prevents an overresponse to the initial light trigger, thus optimizing the seedling deetiolation process. Collectively, the data suggest that at least part of the phy/PIF system acts through these four MIDAs to initiate and optimize seedling deetiolation, and that this mechanism might allow the implementation of spatial (i.e., organ-specific) and temporal responses during the photomorphogenic program.