The greening of etiolated seedlings is crucial for the growth and survival of plants. After reaching the soil surface and sunlight, etiolated seedlings integrate numerous environmental signals and internal cues to control the initiation and rate of greening thus to improve their survival and adaption. However, the underlying regulatory mechanisms by which light and phytohormones, such as abscisic acid (ABA), coordinately regulate greening of the etiolated seedlings is still unknown. In this study, we showed that Arabidopsis (Arabidopsis thaliana) DE-ETIOLATED1 (DET1), a key negative regulator of photomorphogenesis, positively regulated light-induced greening by repressing ABA responses. Upon irradiating etiolated seedlings with light, DET1 physically interacts with FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and subsequently associates to the promoter region of the FHY3 direct downstream target ABA INSENSITIVE5 (ABI5). Further, DET1 recruits HISTONE DEACETYLASE6 to the locus of the ABI5 promoter and reduces the enrichments of H3K27ac and H3K4me3 modification, thus subsequently repressing ABI5 expression and promoting the greening of etiolated seedlings. This study reveals the physiological and molecular function of DET1 and FHY3 in the greening of seedlings and provides insights into the regulatory mechanism by which plants integrate light and ABA signals to fine-tune early seedling establishment.

黄化苗木的绿化对于植物的生长和生存至关重要。达到土壤表面和阳光后，黄化的幼苗整合了许多环境信号和内部线索，以控制绿化的发生和速率，从而提高其存活率和适应性。但是，光和植物激素（如脱落酸（ABA））协调调节黄化幼苗绿化的潜在调控机制仍然未知。在这项研究中，我们证明了拟南芥（Arabidopsis thaliana）DE-ETIOLATED1（DET1）是光形态发生的关键负调节剂，通过抑制ABA反应来正向调节光诱导的绿化。用光照射黄化的幼苗后，DET1与FAR-RED ELONGATED HYPOCOTYL3（FHY3）发生物理相互作用，并随后与FHY3直接下游目标ABA INSENSITIVE5（ABI5）的启动子区域关联。此外，DET1将组蛋白DEACETYLASE6募集到ABI5启动子的位点，并减少了H3K27ac和H3K4me3修饰的富集，因此随后抑制了ABI5表达并促进黄化幼苗的绿化。这项研究揭示了DET1和FHY3在幼苗绿化中的生理和分子功能，并为调节植物整合光和ABA信号以微调幼苗早期建立的调控机制提供了见识。