The Phytohormone Ethylene and Transcriptional Repression
Zhang et al. investigate histone deacetylase in the ethylene response. Plant Cell (2017). https://doi.org/10.1105/tpc.17.00671
By Fan Zhang
Background: Ethylene is the only gaseous hormone in plants, and is a key hormone controlling plant growth and resistance to stress. Epigenetic mechanisms are an important means of gene regulation, including histone acetylation and deacetylation, controlled by histone acetyltransferases and histone deacetylases, respectively. Generally, histone acetylation promotes transcriptional activation, whereas histone deacetylation mediates transcriptional repression.
Question: We previously demonstrated how ethylene promotes transcriptional activation through histone acetylation, but we want to know whether ethylene also regulates transcriptional repression, and if histone deacetylase participates in this process. We tested this by screening the interaction of histone deacetylase with the key components of ethylene signaling pathway and then checking how they regulate gene expression.
Findings: We found that the Arabidopsis srt1 srt2 double mutant shows ethylene insensitive phenotype, and histone deacetylases SRT1 and SRT2 interact with ENAP1 protein, which is important for histone acetylation. Further, by transcriptome analysis, we found that SRT1/SRT2 mainly acts on ethylene down-regulated genes to repress their expression. In addition, SRT1/SRT2 mainly functions on H3K9 acetylation (H3K9Ac) to maintain the low level of this histone mark in response to ethylene. Finally, we demonstrated that srt1 srt2 can suppress the ethylene hypersensitive phenotype of an ENAP1 overexpression transgenic line, further confirming that SRT1/SRT2 is involved in ethylene-mediated transcriptional repression.
Next steps: The most important question is how does SRT1/SRT2 recognize the specific loci of ethylene-repressed genes in response to ethylene? And how is SRT1/SRT2 recruited to these sites by interacting with ENAP1?
Fan Zhang, Likai Wang, Eun Esther Ko, Kevin Shao and Hong Qiao. (2017). Histone Deacetylases SRT1 and SRT2 Interact with ENAP1 to Mediate Ethylene-induced Transcriptional Repression. Published January 2018. DOI: https://doi.org/10.1105/tpc.17.00671
