| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 101 === Changes of light and various stress signals are essential for plant physiological determination. ERF1(Ethylene Response Factor 1) is a component in both jasmonic acid(JA) and Ethylene(ET) signaling, and has been reported undergoing degradation under dark condition. Our previous study showed ERF1 could differentially regulate stress-related genes by binding to their promoters in response to different stress signals. However, the underlying mechanisms of degradation and downstream regulation of ERF1 remain unclear. Here, we confirmed that ERF1 was degraded under dark through 26S proteasome system. Using yeast two-hybrid(Y2H) screening, an E2 ligase, SCE1, and a mediator subunit (At4g25210) were found to physically interact with ERF1. Bimolecular fluorescence complementation(BiFC) assays were carried out to further confirm the interactions between ERF1 and its interacting candidates. Y2H also confirmed the interaction between ERF1 and COP1, which is an important negative regulator and an E3 ligase in light signaling. Moreover, our quantitative reverse transcription PCR(qRT-PCR) results revealed that the direct downstream genes of ERF1, such as delta1-Pyrroline-5-Carboxylate Synthase 1(P5CS1), would be down-regulated under dark. The higher proline level in ERF1 overexpressing plants quickly decreased under dark, which resulted in the less-tolerant phenotype to salt stress in short-day condition. These results indicate that the degradation of ERF1 under dark might be regulated by COP1, and ERF1 regulates the proline level rhythmically by directly activating P5CS1 expression.
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