EIN3 and PIF3 interdependently repress chloroplast development in buried seedlings

During embryogenesis, plastids arrest their differentiation as etioplasts (characterized by the distinctive prolamellar bodies, PLBs), and remain poised  to complete their differentiation into functioning chloroplasts upon exposure to light. Liu et al. explored the factors that interact to effect this developmental pausing. Previously, the transcription factors EIN3 and PIF3 have each been shown to repress transcription of key photosynthetic genes and chloroplast differentiation. Ethylene accumulates in soil and represses hypocotyl growth, as well as expression of light-responsive genes. The authors show that EIN3 and PIF3 form a “physically-interactive transcription factor pair” that binds to target promoters to repress transcription. Therefore, the combined signals of darkness (which stabilizes PIF3) and ethylene accumulation together suppress the developmental transition from etioplast to chloroplast. (Summary by Mary Williams)  Plant Cell 10.1105/tpc.17.00508