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 ( http://dx.doi.org/10.1073/pnas.1718377115).

 

This work was supported by the National Natural Science Foundation of China, the 973 project and the State Key Lab of Plant Genomics.

 

 

 

 

Contact:

Dr. ZHANG Jinsong

Email: jszhang@genetics.ac.cn