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Plan Development week 6 notes

by: carte226

Plan Development week 6 notes bio 523

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All notes for week 6, second set of notes for exam 2 material
Plant Development
Dr. Krizek
Class Notes
Ethylene, signaling
25 ?




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This 6 page Class Notes was uploaded by carte226 on Thursday October 13, 2016. The Class Notes belongs to bio 523 at University of South Carolina taught by Dr. Krizek in Fall 2016. Since its upload, it has received 4 views. For similar materials see Plant Development in Plant Biology at University of South Carolina.


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Date Created: 10/13/16
Ethylene receptors: ETR1 Hybrid HIS Kinase ETR1-1: ETHYLENE INSENSITIVE Dominant mutation Don’t know if the receptors are positive or negative regulators of ethylene responses Signaling component: CTR1 Raf-like MAPKKK Ctr1-1: constitutive triple response phenotype - Negative regulator of ethylene responses Genetic Model Ethylene ETR1 CTR1 –I Ethylene responses ERS1 ERS2 ETR2 EIN4 + OFF ON _ ON OFF ^^^ don’t know information yet to explain the gaps sooo…^^^ Need LOF alleles in the ethylene receptors Reverse genetics: single mutant allele Make double and higher order mutants T-DNA insertional mutant allele for all 5 ethylene receptors Single mutants: show no dramatic phenotype Look like WT Respond normally to ethylene Double mutants: etr1-9, ers1-3 showed a constitutive triple response (lost two ethylene receptors) (look like ctr1-1 mutant) Loss of 2 class 1 receptors Triple mutants: etr1 etr2 ein4 (lost three ethylene receptors) Gave a constitutive triple response Quad mutant: etr1, etr2, ein4, ers2 Gave a constitutive triple response LOF in the ethylene receptors is a constitutive triple response (even when there is no added exogenous ethylene, the plants act like they are in ethylene) - So the ethylene receptors are negative regulators of ethylene responses ETR1, ERS1, ETR2, ERS2, EIN4: repress ethylene responses in the absence of ethylene - Ethylene binding inactivates the receptors Model: ETR1 C2H4 –I ETR2  CTR1 --I ethylene responses ERS1 ERS2 EIN4 + OFF OFF ON _ ON ON OFF Mutations in ethylene receptors: 1. Loss of function ethylene receptor mutants a. EX: Etr1-9 ers1-3: constitutive triple response b. Dominant ethylene receptor mutants: i. Etr1-1: gave an ethylene resistance / ethylene insensitive 1. Never gave the triple response even when ethylene added to system ii. Basis for dominance: How are the proteins encoded by the dominant alleles acting? iii. Dominant alleles: 1. Hypermorph: mutation that results in an increase in normal gene function o Constitutively active protein (protein is stuck in the ON signaling state; it cant be turned off) 2. Antimorph: (dominant negative): mutation that acts in opposition to the normal gene function o Mutant protein interferes with the normal protein o In this case, the dominant mutant phenotype is the same as the recessive loss of function phenotype 3. Neomorph: mutation results in a gain of a new function that is different from the normal function of the gene All of the dominant etr1 alleles have mutations in the ethylene binding region of the protein - Normally ethylene binding to the WT receptors inactivates the receptors - Mutant proteins encoded by the dominant alleles could not bind ethylene and thus could not be switched off - Mutant proteins were constitutively active o Acting as hypermorphs Genetic Model WT ethylene –I ethylene receptors  CTR1 --I ethylene responses + OFF OFF ON _ ON ON OFF Etr1-1 dominant allele Ethylene --I receptors  CTR1 --I responses + ON ON OFF _ ON ON OFF Ethylene insensitive Etr1-9, ers1-3 recessive alleles ethylene –I ethylene receptors  CTR1 --I ethylene responses + OFF OFF ON _ OFF OFF ON Constitutive triple response Additional signaling components: 1. EIN2 : positive regulator of ethylene responses  protein has sequence similarity to NRAMP metal ion transporters  consists of an amino terminal hydrophobic region which consists of 12 transmembrane and 9 carboxy terminal hydrophobic region with a NLS  reside in ER membrane; physically interacts with receptors  protein accumulates upon ethylene treatments  required for stabilization of a transcription factor called EIN 3  amino terminal part of the EIN2 detects the status of the early ethylene signaling components (receptors, ( ^ R1) and relays that information to the downstream transcription factors in the nucleus EIN2 in the presence of ethylene: - EIN2 is not phosphorylated - EIN2 is cleaved - C term portion of EIN2 moved from the ER to the nucleus EIN2 in the absence of ethylene: - EIN2 is phosphorylated by CTR1 - EIN2 is not cleaved - No message is related to the nucleus Transcription factors that promotes ethylene responses: 1. EIN3/ EILs a. Short lived proteins that function as fimers b. TFs that bind the promotors of ethylene-inducible gene and activate their expression c. Some targets: (all work in turning down ethylene responses) i. ERFs (ethylene response factors): TFs that bind to ethylene response elements (ERFs) in the promoters of ethylene-inducible gene ii. ETR2 : results in the production of a new batch of ethylene receptors iii. EBF2: F box protein that acts in the degradation of EIN3 EIN2 & EIN3 are regulated by Ubiquitin-proteasome mediated degradation - Involves CULLIN-RING type of E3 ubiquitin ligating enzyme SCF o SKP 1 o CULLIN o F box protein (component of the complex that recognizes the target protein) - EIN2 & EIN3 are stabilized by ethylene (degraded in the absence of ethylene) - EIN2 o ETP1, ETP2 (EIN2 targeting protein) - EIN3 o EBF1, EBF2 (EIN3 binding F box protein) Ethylene –I ethylene receptors  CTR1 –I EIN2  EIN3 ERFs  ethylene responses + OFF OFF ON ON ON ON _ ON ON OFF OFF OFF OFF ^(neg reg of ethylene res)^ ^(pos reg of eth sig)^ EIN2 & EIN3 are regulated post translationally Ethylene present: 1. Perception of ethylene by a family of ethylene receptors (ER; dimerize). Ethylene inactivates the receptors 2. Inactive ethylene receptors cause a conformal change in CTR1 that reduces its kinase activity (CTR1 inactive) 3. EIN2 Is not phosphorylated by CTRa. EIN is cleaved and the C terminal portion moves into the nucleus. 4. EIN2 induces the degradation of EBF1&2. EIN3 accumulates in the nucleus 5. EIN3 turns on ethylene-inducible genes like ERFs 6. ERFs induce additional ethylene inducible genes 7. Ethylene responses turned on Ethylene absence: 1. Ethylene receptors are active and activate CTR1 2. CTR1 phosphorylates EIN2 and this results in inactivating ETR2 3. Degradation of EIN3 in the nucleus 4. Ethylene-induced genes are not expressed 5. No ethylene response


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