Project description:A complex interplay between ethylene, ETP1/ETP2 F-box proteins, and degradation of EIN2 is essential for triggering ethylene responses in plants. The gaseous plant hormone ethylene can trigger myriad physiological and morphological responses in plants. While many ethylene signaling pathway components have been identified and characterized, little is known about the function of the integral membrane protein EIN2, a central regulator of all ethylene responses. Here, we demonstrate that Arabidopsis thaliana EIN2 is a protein with a short half-life that undergoes rapid proteasome-mediated protein turnover. Moreover, EIN2 protein accumulation is positively regulated by ethylene. We identified two F-box proteins, EIN2 TARGETING PROTEIN and 2 (ETP1 and ETP2), that interact with the EIN2 carboxyl-terminal domain (CEND), which is highly conserved and sufficient to activate most ethylene responses. Overexpression of ETP1 or ETP2 disrupts EIN2 protein accumulation, and these plants manifest a strong ethylene insensitive phenotype. Furthermore, knocking down the levels of both ETP1 and ETP2 mRNAs using an artificial microRNA (amiRNA) leads to accumulation of EIN2 protein, resulting in plants that display constitutive ethylene response phenotypes. Finally, ethylene down-regulates ETP1 and ETP2 proteins, impairing their ability to interact with EIN2. Thus, these studies reveal that a complex interplay between ethylene, the regulation of ETP1/ETP2 F-box proteins, and subsequent targeting and degradation of EIN2 is essential for triggering ethylene responses in plants. Keywords: ethylene treatment, genetic modification
Project description:A complex interplay between ethylene, ETP1/ETP2 F-box proteins, and degradation of EIN2 is essential for triggering ethylene responses in plants. The gaseous plant hormone ethylene can trigger myriad physiological and morphological responses in plants. While many ethylene signaling pathway components have been identified and characterized, little is known about the function of the integral membrane protein EIN2, a central regulator of all ethylene responses. Here, we demonstrate that Arabidopsis thaliana EIN2 is a protein with a short half-life that undergoes rapid proteasome-mediated protein turnover. Moreover, EIN2 protein accumulation is positively regulated by ethylene. We identified two F-box proteins, EIN2 TARGETING PROTEIN and 2 (ETP1 and ETP2), that interact with the EIN2 carboxyl-terminal domain (CEND), which is highly conserved and sufficient to activate most ethylene responses. Overexpression of ETP1 or ETP2 disrupts EIN2 protein accumulation, and these plants manifest a strong ethylene insensitive phenotype. Furthermore, knocking down the levels of both ETP1 and ETP2 mRNAs using an artificial microRNA (amiRNA) leads to accumulation of EIN2 protein, resulting in plants that display constitutive ethylene response phenotypes. Finally, ethylene down-regulates ETP1 and ETP2 proteins, impairing their ability to interact with EIN2. Thus, these studies reveal that a complex interplay between ethylene, the regulation of ETP1/ETP2 F-box proteins, and subsequent targeting and degradation of EIN2 is essential for triggering ethylene responses in plants. Experiment Overall Design: Six samples were analyzed. There were three treatments with two biological replicates each. The treatments are as follows: 8 week old Col-0 plants (air control), 8 week old Col-0 plants treated for 24 hours with ethylene gas (10 ppm), and artificial microRNA knockdown mutants, amiR-ETP1/2.
Project description:Ethylene gas is essential for many developmental processes and stress responses in plants. ETHYLENE INSENSITIVE2 (EIN2), an NRAMP-homologous integral membrane protein, plays an essential role in ethylene signaling but its function remains enigmatic. Here we report that phosphorylation-regulated proteolytic processing of EIN2 triggers its endoplasmic reticulum (ER)-nucleus translocation, which is essential for hormone signaling and response in Arabidopsis. Without ethylene, or in hormone receptors mutants, ER-tethered EIN2 shows CTR1 kinase-dependent phosphorylation. Ethylene exposure triggers dephosphorylation and proteolytic cleavage, resulting in rapid nuclear translocation of a carboxyl-terminal EIN2 fragment (C’). Plants containing mutations that mimic EIN2 dephosphorylation, or inactivate CTR1, show constitutive cleavage and nuclear localization of EIN2-C’, and EIN3/EIL1-dependent activation of ethylene responses. These findings uncover a mechanism of subcellular communication whereby ethylene gas stimulates rapid phosphorylation-dependent cleavage and nuclear movement of the EIN2-C’ peptide, thus linking hormone perception and signaling components located in the ER with nuclear-localized transcriptional regulators.
Project description:Ethylene is a gaseous plant growth regulator that controls a multitude of developmental and stress responses. Recently, the levels of Arabidopsis EIN3 protein, a key transcription factor mediating ethylene-regulated gene expression, have been demonstrated to increase in response to the presence of ethylene gas. Furthermore, in the absence ethylene, EIN3 is quickly degraded through a ubiquitin/proteasome pathway mediated by two F box proteins, EBF1 and EBF2 (1-3). Here, we report the identification of ETHYLENE INSENSITIVE5 as the 5’?3’ exoribonuclease XRN4. Specifically, we demonstrate that EIN5 is a component of the ethylene signal transduction cascade acting downstream of CTR1 that is required for ethylene-mediated gene expression changes. Furthermore, we find that the ethylene insensitivity of ein5 mutant plants is a consequence of the over-accumulation of EBF1 and EBF2 mRNAs resulting in the under-accumulation of EIN3 even in the presence of ethylene gas. Together, our results suggest that the role of EIN5 in ethylene perception is to antagonize the negative feedback regulation on EIN3 by promoting EBF1 and EBF2 mRNA decay, which consequently allows the accumulation of EIN3 protein to trigger the ethylene response. Keywords: total RNA profiling, proteolysis, plant hormoine, ethylene
Project description:Ethylene is a gaseous plant hormone that regulates plant growth and development. Broad reprogramming of gene expression is required for ethylene responses. The primary ethylene transcription factor (TF) ETHYLENE INSENSITIVE3 (EIN3) drives expression of secondary TFs including the ETHYLENE RESPONSE DNA-BINDING FACTORS (EDFs), but the role of the EDFs within the ethylene genome regulatory network is not understood. Here, we describe an investigation into the function of the EDFs in ethylene signalling and hormonal cross-regulation. We determined the target genes and binding dynamics of EDFs 1, 2, 3 during an ethylene response and the effects of edf1234 quadruple mutation on gene expression. The EDFs and EIN3 shared a large proportion of their target genes but had different functions. The EDFs were associated with repression of target genes, but this was superseded by activation when EIN3 bound the same genes. Genes important in other hormone signalling pathways, in particular abscisic acid (ABA), were targets of the EDFs. This demonstrates how ethylene engages hormonal cross-regulation to repress genes in competing signalling pathways and prioritize itself.
Project description:We report that CBP20 phosphorylation can regulate root growth in ethylene. We examined the small RNA expression in roots and shoots of wild type (Col) and cbp20 mutant (in Col background). Ethylene is one of the most essential hormones for plant developmental processes and stress responses. EIN2 is a key factor in ethylene signaling pathway and its function is regulated by phosphorylation. However, the phosphorylation regulation in the ethylene signaling pathway is largely unknown. Here we report the phosphorylation of CBP20 is regulated by ethylene, and the phosphorylation is involved in root elongation. The constitutive phosphorylation format of CBP20 rescues the cbp20 root ethylene hyposensitive phenotype, while the constitutive de-phosphorylation format of CBP20 is unable to rescue the root phenotype of cbp20 in response to ethylene. Genome wide study on ethylene regulated gene expression and microRNA expression in the roots and shoots of both Col and cbp20, together with the result of genetics validation suggest that ethylene induced phosphorylation of CBP20 is involved in root growth and one pathway is through the regulation of microRNAs and their target genes in roots.