Abstract
As an ideal model for studying ethylene effects on cell elongation, Arabidopsis hypocotyl growth is widely used due to the unique characteristic that ethylene stimulates hypocotyl elongation in the light but inhibits it in the dark. Although the contrasting effect of ethylene on hypocotyl growth has long been known, the molecular basis of this effect has only gradually been identified in recent years. In the light, ethylene promotes the expression of PHYTOCHROME INTERACTING FACTOR 3 (PIF3) and the degradation of ELONGATED HYPOCOTYL 5 (HY5) protein, thus stimulating hypocotyl growth. In the dark, ETHYLENE RESPONSE FACTOR 1 (ERF1) and WAVE-DAMPENED 5 (WDL5) induced by ethylene are responsible for its inhibitory effect on hypocotyl elongation. Moreover, CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and PHYTOCHROME B (phyB) mediate the light-suppressed ethylene response in different ways. Here, we review several pivotal advances associated with ethylene-regulated hypocotyl elongation, focusing on the integration of ethylene and light signaling during seedling emergence from the soil.
Highlights
As cell division rarely occurs in the Arabidopsis hypocotyl, this system is considered an ideal model for studying cell elongation (Vandenbussche et al, 2005; Boron and Vissenberg, 2014)
As seedlings grow toward the soil surface, ethylene production is reduced with decreased mechanical stress; the gradual increase in light penetrating through the soil will suppress CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) activity, promoting EIN3-BINDING F BOX PROTEIN 1 (EBF1)/2-mediated EIN3 degradation and relieving the inhibitory effect of ethylene on hypocotyl growth (Shi et al, 2016a)
This mini review aimed to concisely summarize the crosstalk between ethylene and light signaling in the regulation of hypocotyl growth, focusing on detailing the function of ethylene in hypocotyl growth during seedling emergence
Summary
As cell division rarely occurs in the Arabidopsis hypocotyl, this system is considered an ideal model for studying cell elongation (Vandenbussche et al, 2005; Boron and Vissenberg, 2014). The hypocotyl is highly responsive to both internal and external cues, such as plant hormones, light, temperature, and gravity (Vandenbussche et al, 2005; Van de Poel et al, 2015) Among these growth regulators, ethylene is special because of its contradictory effect on hypocotyl elongation (Ecker, 1995; Smalle et al, 1997). The application of ethylene or its precursor 1aminocyclopropane-1-carboxylic acid (ACC) stimulates hypocotyl elongation, whereas in the dark, ethylene suppresses hypocotyl growth (Zhong et al, 2012; Yu et al, 2013). Light signaling is perceived by various photoreceptors and leads to the modulation of downstream transcription factors such as PHYTOCHROME INTERACTING FACTORs (PIFs) and HYPOCOTYL 5 (HY5) (Lau and Deng, 2010). We present an overview of ethylene function during hypocotyl elongation, focusing on the interaction between ethylene and light signaling, especially during seedling emergence
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