Mutations in the Arabidopsis ETHYLENE-INSENSITIVE3 (EIN3) gene severely limit a plant's response to the gaseous hormone ethylene.ein3 mutants show a loss of ethylene-mediated effects including gene expression, the triple response, cell growth inhibition, and accelerated senescence. EIN3 acts downstream of the ER-localized histidine kinase ethylene receptor, ETR1, and the Raf-like kinase, CTR1 (constitutive triple response 1). TheEIN3 gene encodes a novel nuclear-localized protein that shares sequence similarity, structural features, and genetic function with three EIN3-LIKE (EIL) proteins. In addition to EIN3, EIL1 or EIL2 were able to complement ein3, suggesting their participation in the ethylene signaling pathway (Binder 2020). Overexpression of EIN3 or EIL1 in wild-type or ethylene-insensitive2 plants conferred constitutive ethylene phenotypes, indicating their sufficiency for activation of the pathway in the absence of ethylene. The increase in EIN3, EIL1, and EIL2 activity caused by EIN2-C leads to changes in the transcription of other ethylene response genes, including other transcription factors, such as the ERFs.
There are at least 8 EIL members in maize that harbor a conserved domain (PF04873). The ZmEIL1 gene has been characterized. Sequence comparison of the ZmEIL1 protein with other EIN3/EILs proteins revealed high conservation of five alpha-helices that could form a V-shaped cleft in a 3-D model, just like AtEIL3 in Arabidopsis thaliana. This protein showed transcriptional activation in yeast with the activation domain located within the 507 - 647 amino acid region. Furthermore, ZmEIL1 could interact with ZmERF1 in the yeast systems, which was downstream response factor in ethylene signal transduction pathway. ZmEIL1 mRNA could be highly induced in maize seedlings by ethephon and 1-methylcyclopropene treatments. Meanwhile, ZmEIL1 showed relatively high expression at 20 d after pollination in maize kernel. These results show that ZmEIL1 played an important role in the growth and development by participating in ethylene signaling pathway in maize (Shi et al., 2017).