In plants, flowering time is controlled by environmental signals such as day-length and temperature. H3K27me3 is highly conserved histone modification, which facilitates the maintenance of developmentally regulated genes in a transcriptionally repressed state in both plants and animals. The establishment and removal of H3K27me3 at specific genes is therefore critically important for normal development, including flowering.
Recently, a team led by Prof. CAO Xiaofeng at Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), in collaboration with Prof. SUN Daye’s team from Hebei Normal Unviersity and Prof. DU Jiamu’s team from Shanghai Center for Plant Stress Biology, CAS, revealed the structure of Arabidopsis JUMONJI13 (JMJ13) catalytic domain and its function in photoperiod and temperature-dependent flowering responses.
The researchers found that JMJ13 has specific H3K27me3 demethylase activity in vitro and in vivo, but no significant activity on H3K27me2 and H3K27me1. The crystal structure of the JMJ13 catalytic domain in complex with its substrate peptide reveals that H3K27me3 is specifically recognized through hydrogen bonding and hydrophobic interactions. Interestingly, they found that JMJ13 and UTX, a human H3K27me3 demethylase, have evolved different specific interactions to ensure substrate specificity.
Interestingly, the researchers found that JMJ13 represses flowering in long-day (LD) conditions, regardless of low or high temperatures. However, jmj13 plants flowered early at higher temperature (28 °C), but not at lower temperatures, when grown in short-day (SD) conditions, indicating JMJ13 is an important regulator response for both temperature and day-length. They further show that the enzyme activity is necessary for JMJ13 function and the genetic interaction between JMJ13 and other flowering time regulators.
These results reveal JMJ13-mediated H3K27me3 demethylation is a new mechanism regulating temperature- and photoperiod-dependent flowering regulation. “These results not only help us to understand more about flowering regulation, but can potentially help us improve crop adaptation in the future, for JMJ13 homologs are conserved in different species.” Said Dr. Shuzhi Zheng, first author of this paper.
Figure 1. JMJ13 negatively modulates flowering time in a temperature- and photoperiod-dependent manner. (Image by IGDB)
Figure 2. Structures of JMJ13-a-KG and JMJ13-NOG-H3K27me3 complexes. (Image by IGDB)
Contact:
Mr. QI Lei
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences
