Fig. 6: Translational regulation of ethylene signaling is dependent on MHZ9.

Analysis of ethylene-induced alterations at a RNA, b translational, and c translation efficiency (TE) levels in WT. Two-day-old etiolated seedlings were treated with or without 10 μL/L of ethylene for 4 h and then were subjected to RNA-seq and ribosome footprints (Ribo-seq) analysis with two bioreplicates, respectively. The genes with RPM more than 0 were selected for differential genes identification. The black dashed line indicates the 0.05 P value cutoff. d Comparison of the ethylene-responsive genes at mRNA (top), translational (middle), and TE (bottom) levels in WT and mhz9. The significantly differentially expressed genes in WT were compared with that in mhz9 using Venn diagrams (Venny 2.0). e Distribution of log₂ fold-changes of the 1956 TE-differential genes in WT and mhz9. The alterations of mRNA (f), translational (g), and TE (h) levels of the 555 MHZ9-binding genes (with both RNA-seq and Ribo-seq read > 0 RPM) in WT and mhz9 during ethylene response. f–h **P < 0.01, NS, not significant. i KEGG analysis at the translational, mRNA, and translation efficiency (TE) levels in response to ethylene. The log₂FC (ET/Air) of each pathway was the average of log₂FC of its contained genes. The pathways with statistically significant differences compared to the average of all pathway genes were selected and divided into up-regulated (top) and down-regulated (bottom) based on Ribo-seq (*P < 0.05, **P < 0.01; Mann–Whitney U test). The number of n indicates gene numbers contained in each pathway. j A proposed MHZ9 working model. In the absence of ethylene, MHZ9 remains at low-affinity-binding states to OsEBFs mRNA. OsEBFs proteins accumulate and lead to the degradation of OsEIL1. Ethylene-response is OFF. With ethylene, MHZ9 possibly receives a signal from OsEIN2-C through direct interaction, and then binds to the 3′UTR of OsEBFs mRNA and other targets for translational inhibition, which contributes to the OsEIL1 protein accumulation and downstream ethylene signaling. The residual OsEBF1/2 may decay through unknown mechanisms.