Abstract
Copper ions play an important role in ethylene receptor biogenesis and proper function. The copper transporter RESPONSIVE-TO-ANTAGONIST1 (RAN1) is essential for copper ion transport in Arabidopsis thaliana. However it is still unclear how copper ions are delivered to RAN1 and how copper ions affect ethylene receptors. There is not a specific copper chelator which could be used to explore these questions. Here, by chemical genetics, we identified a novel small molecule, triplin, which could cause a triple response phenotype on dark-grown Arabidopsis seedlings through ethylene signaling pathway. ran1-1 and ran1-2 are hypersensitive to triplin. Adding copper ions in growth medium could partially restore the phenotype on plant caused by triplin. Mass spectrometry analysis showed that triplin could bind copper ion. Compared to the known chelators, triplin acts more specifically to copper ion and it suppresses the toxic effects of excess copper ions on plant root growth. We further showed that mutants of ANTIOXIDANT PROTEIN1 (ATX1) are hypersensitive to tiplin, but with less sensitivity comparing with the ones of ran1-1 and ran1-2. Our study provided genetic evidence for the first time that, copper ions necessary for ethylene receptor biogenesis and signaling are transported from ATX1 to RAN1. Considering that triplin could chelate copper ions in Arabidopsis, and copper ions are essential for plant and animal, we believe that, triplin not only could be useful for studying copper ion transport of plants, but also could be useful for copper metabolism study in animal and human.
Highlights
The phytohormone ethylene (C2H4) plays important roles in plant growth and development
Arabidopsis wild type Columbia-0 (Col-0) were grown and screened against a synthetic small molecule library with 12,000 compounds in the dark for 3 days. Those compounds that caused a triple response in seedlings were selected and their chemical genetics effects were retested. From this plant chemical screening, we acquired 14 compounds which cause a triple response in dark-grown Arabidopsis seedlings
Using the ethylene perception inhibitor, AgNO3, and the ethylene insensitive mutant ein2-5, we found that only a compound we called triplin (1-(1-morpholino-1-(thiophen-2-yl) propan-2-yl)-3-(2-(trifluoromethoxy) phenyl) thiourea) worked through the ethylene signaling pathway (Fig 1 and S1 Fig)
Summary
The phytohormone ethylene (C2H4) plays important roles in plant growth and development. When exposed to ethylene gas for 3 days, dark-grown Arabidopsis seedling shows a typical triple response phenotype including a short hypocotyl and root, larger diameter hypocotyl, and an exaggerated apical hook [1,2]. ETHYLENE RESPONSE1 (ETR1), ETHYLENE RESPONSE2 (ETR2), ETHYLENE RESPONSE SENSOR1 (ERS1), ETHYLENE RESPONSE SENSOR2 (ERS2) and ETHYLENE INSENSITIVE4 (EIN4) are five ethylene receptors in Arabidopsis which function redundantly and negatively to regulate ethylene signaling and responses. The receptors signal is transferred to a downstream Raf-like protein kinase CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) [3,4]. CTR1 interacts with and phosphorylates an endoplasmic reticulum (ER) membrane-localized Nramp homolog ETHYLENE IN SENSITIVE 2 (EIN2). This prevents EIN2 from activating downstream components of ethylene signaling including ETHYLENE INSENSITIVE3 (EIN3) and EIN3-LIKE1 (EIL1). When ethylene binds to the receptors, the phosphorylation of EIN2 by CTR1 is reduced, leading to accumulation of EIN2 and proteolytic cleavage of the cytosolic C-terminal domain of EIN2, which enters the nucleus to initiate ethylene signaling [5,6,7,8,9,10]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
