[Wan-Sheng Lo] Arabidopsis JMJ17 promotes cotyledon greening during de-etiolation by repressing genes involved in tetrapyrrole biosynthesis in etiolated seedlings

The dynamic histone lysine methylation on histone H3 is associated with diverse biological processes in both plants and animals. Arabidopsis histone H3 lysine 4 (H3K4) demethylases play crucial roles in regulating flowering time, dehydration stress response and leaf senescence, but its involvement in seedling establishment remains unexplored. We show that Arabidopsis JMJ17, an H3K4me3 demethylase, is involved in cotyledon greening during seedling establishment. Upon light eradiation, etiolated jmj17 seedlings displayed decreased cotyledon greening and reduced chlorophyll level compared to wild type; overexpression of JMJ17 completely rescued the jmj17 mutant phenotype. Furthermore, results from ChIP-qPCR and RT-qPCR analyses revealed that JMJ17 directly associates with the promoter of key genes involved in tetrapyrrole biosynthesis in the dark to repress gene expression but dissociates during light exposure. By using yeast-two hybrid assay, we found that JMJ17 association with gene promoters is potentially dependent on PIF1 in the dark. Our study reveals a new functional role of histone demethylase JMJ17 in controlling cotyledon greening in etiolated seedlings during the dark-to-light transition, which plays a crucial role in the growth and survival of plants. We dedicate this article with love and thanks to the memory of our kind and dear mentor and colleague, Dr. Wan-Sheng (Sunny) Lo, who passed away in the course of submission of this manuscript. Dr. Wan-Sheng Lo was the principal investigator of this work in collaboration with Dr. Long-Chi Wang. https://nph.onlinelibrary.wiley.com/share/YNE7MGGPMCXKS4ZUTVIB?target=10.1111/nph.17327