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Chinese Scientists Discover a New Regulator of Ethylene Signaling
The phytohormone ethylene regulates many aspects of plant growth and development. EIN2 is the central component of ethylene signaling pathway, and its turnover is crucial for triggering ethylene responses. The N-terminus of EIN2 has an Nramp-like domain that consists of 12 predicted transmembrane helices, and its C-terminus has a large hydrophilic domain. Although extensive studies have revealed that the C-terminal domain of EIN2 can be cleaved and translocated into the nucleus and P-body to activate downstream signaling, the importance and regulation of its N-terminal Nramp-like domain have long been unknown.
In a recent study, researchers from Prof. ZHANG Jinsong and Prof. CHEN Shouyi’s groups at the Institute of Genetics and Development Biology, Chinese Academy of Sciences, identified a new regulator MHZ3 through characterizing of an ethylene-insensitive mutant mhz3 in rice (Fig. 1A).
The researchers found that MHZ3 encodes a previously uncharacterized ER membrane protein that genetically acts at and physically interacts with OsEIN2. MHZ3 associates with the OsEIN2 Nramp-like domain to stabilize the protein by inhibiting ubiquitination and proteasome-mediated degradation (Fig. 1B).
This study reveals the roles of MHZ3 in stabilizing the OsEIN2 and maintaining ethylene signaling, and strengthens importance of OsEIN2 N-terminal transmembrane domains in mediating upstream ethylene signals, providing insights into the mechanisms of OsEIN2 N-terminal domain in ethylene signaling.
This work entitled “Membrane protein MHZ3 stabilizes OsEIN2 in rice by interacting with its Nramp-like domain”, has been published online on February 20, 2018 in PNAS
This work was supported by the National Natural Science Foundation of China, the 973 project and the State Key Lab of Plant Genomics.
Fig.1, MHZ3 stabilizes OsEIN2 for ethylene signaling. (A) Ethylene-response phenotype of mhz3. ET: ethylene treatment. (B) A proposed model for MHZ3 stabilizing OsEIN2. MHZ3 interacts with OsEIN2 to inhibit its ubiquitination and degradation for stabilization during ethylene signaling. (Image by IGDB)
Dr. ZHANG Jinsong