OsELF3 Rhythmicity Affects Flowering under Long-day Conditions
Zhu et al. identify OsELF3 ubiquitination and degradation by HAF1 in rice. The Plant Cell (2018). https://doi.org/10.1105/tpc.18.00653
By Changyin Wu
Background: The photoperiodic response is one of the most important factors determining heading date in rice. Ubiquitin-mediated protein degradation is essential for rhythmicity of flowering regulators. HAF1, a C3HC4 RING domain-containing E3 ubiquitin ligase, is essential to precisely modulate the Hd1 accumulation to enable rice heading under shorter-day conditions. We know a circadian clock gene, OsELF3, promoters rice heading under long-day conditions (LDs). However, little is known about the molecular mechanisms of OsELF3 accumulation during the photoperiodic response.
Question: We wanted to know if HAF1 physically interacts with OsELF3 for its accumulation under LDs. We therefore tested the possible interactions between HAF1 and OsELF3. Then, we investigated the biological signification of their interaction for heading date in rice.
Findings: We found that OsELF3, a flowering promoter under LDs, physically interacts with HAF1. Moreover, we showed that HAF1 mediates the ubiquitination of OsELF3 protein via the 26S proteasome pathway. HAF1 precisely modulates the diurnal rhythm of OsELF3 accumulation to ensure rice appropriate heading under LDs. Furthermore, an amino acid variation within the interaction domain of OsELF3 with HAF1 strongly affects the variation in heading date among japonica rice accessions.
Next steps: It will be great interest to identify additional heading regulators, which might be ubiquitinated by HAF1. More broadly, the timing of protein accumulation of heading regulators will explain the regional distribution of rice cultivars.
Chunmei Zhu, Qiang Peng, Debao Fu, Dongxia Zhuang, Yiming Yu, Min Duan, Weibo Xie, Yaohui Cai, Yidang Ouyang, Xingming Lian, Changyin Wu (2018). The E3 Ubiquitin Ligase HAF1 Modulates Circadian Accumulation of EARLY FLOWERING3 to Control Heading Date Under Long-day Conditions in Rice. Plant Cell 30: 2352-2367; DOI: https://doi.org/10.1105/tpc.18.00653