Abscisic Acid Antagonizes Ethylene Production through the ABI4-Mediated Transcriptional Repression of ACS4 and ACS8 in Arabidopsis
Zhijun Dong, Yanwen Yu, Shenghui Li, Juan Wang, Sajun Tang and Rongfeng Huang
Increasing evidence has revealed that abscisic acid (ABA) negatively modulates ethylene biosynthesis, although the underlying mechanism remains unclear. To identify the factors involved, we conducted a screen for ABA-insensitive mutants with altered ethylene production in Arabidopsis. A dominant allele of ABI4, abi4-152, which produces a putative protein with a 16-amino-acid truncation at the C-terminus of ABI4, reduces ethylene production. By contrast, two recessive knockout alleles of AB14, abi4-102 and ahid-103, result in increased ethyene evolution. indicatina that ABI4 negatively reaulates ethylene produc tion. Further analyses showed that expression of the ethylene biosynthesis genes ACS4, ACS8, and ACO2.was sianificantly decreased in abi4-152 but increased in the knockout mutants, with partial dependence on.ABA. Chromatin immunoprecipitation-quantitative PCR assays showed that ABI4 directly binds the pro moters of these ethylene biosynthesis genes and that ABA enhances this interaction. A fusion protein containing the truncated AB14-152 peptide accumulated to higher levels than its full-length counterpart in transgenic plants, suggesting that ABI4 is destabilized by its C terminus. Therefore, our results demonstrate that ABA negatively regulates ethylene production through ABI4-mediated transcriptional repression of the ethylene biosynthesis genes ACS4 and ACS8 in Arabidopsis.