Storage oil mobilization (SOM) breaks down the reserve lipids in the seed and converts them to sugar. SOM is essential to support postgermination growth and seedling establishment, which are of foremost importance for plant fitness in the field. Light is the main environmental cue determining the transition between heterotrophic growth based on oil reserves and photoautotrophic growth supported by photosynthesis. SOM is faster in the dark-to-light transition compared to dark, indicating that the regulation of SOM needs to be tuned to the light environment of the emerging seedling. A current challenge is to define how the core enzymes in SOM are co regulated in response to light, which is of special relevance to plant growth and has profound implications in biotechnology. The phytochromeinteracting bHLH transcription factors PIFs are central regulators of plant growth, and are critical in the adaptation of seedlings to their light environment. PIFs have been shown to regulate key enzymes in chlorophyll, carotenoid, and anthocyanin biosynthesis in response to light. Recently, an Arabidopsis mutant deficient in four PIF proteins was found to have reduced oil body content in dark, suggesting that SOM is misregulated in the absence of the PIFs. The main objective of this proposal is to characterize how PIFs might be mediating light regulation of SOM. To achieve this goal, biochemical, metabolomic and molecular biology approaches will be combined to characterize in detail the light regulation of SOM enzymes and the role of the PIFs in their regulation. In addition, a cell biology approach will be used to characterize how SOM and light regulate etioplast development and transition to chloroplasts. Finally, a candidate gene approach will be used to identify novel regulators of SOM. The funding of this proposal will allow the applicant to initiate her own research project in the host laboratory and facilitate her transition to an independent research position in Europe.