CS-9-2 - JMJ17 Promotes Cotyledon Greening During De-etiolation Through Repressing Genes Involved in Tetrapyrrole Biosynthesis in Etiolated Arabidopsis Seedlings

H3K4 (H3K4) demethylases are involved in the various plant developmental processes such as flowering time and circadian clock regulation, salt and dehydration stress response and leaves senescence whereas its involvement in seedling greening and/or chlorophyll biosynthesis is still unknown. Cotyledon greening of etiolated seedling is a crucial process happened in plant to convert it from heterotrophic to autotrophic. During this stage chlorophyll biosynthesis process must be tightly controlled to protect plants from photo-oxidative damage when the etiolated seedling exposed to light. Here, we found that Arabidopsis JMJ17, which is a ubiquitously expressed and nuclear localized H3K4me3 demethylase plays an important role in seedling greening during de-etiolation. Dark-grown loss of function jmj17 mutants displayed higher cotyledon opening rates and accumulated higher protochlorophyllide, while lower greening rates and produced higher reactive oxygen species than wild-type plants upon light irradiation. Overexpression of JMJ17 completely recovered jmj17 loss of function phenotypes. Transcriptome data along with RT-qPCR and ChIP-qPCR revealed that, dark grown jmj17 mutant accumulated significantly higher level of H3K4me3 and activated key tetrapyrrole biosynthesis (TPB) genes such as PORC, HEMA1, CHLI1 and CHLM   as well as LHCA4. Importantly JMJ17 binding was significantly enriched above gene promoters in the dark while dissociated from promoters upon light irradiation. Our study emphasizes the essential role of JMJ17 in enhancing seedling greening and survival through protecting etiolated seedlings against photo-oxidative damage.
 

Coauthors: Wan-Sheng Lo – Institute of Plant and Microbial Biology, Academia Sinica;Long-Chi Wang – Department of Life science, National Chung Hsing University