Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.25 (MEKK1)
 1,856 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The enhanced disease resistance 1 (edr1) mutation of Arabidopsis confers resistance to powdery mildew disease caused by the fungus Erysiphe cichoracearum. Resistance mediated by the edr1 mutation is correlated with induction of several defense responses, including host cell death. Double mutant analysis revealed that all edr1-associated phenotypes are suppressed by mutations that block salicylic acid (SA) perception (nim1) or reduce SA production (pad4 and eds1). The NahG transgene, which lowers endogenous SA levels, also suppressed edr1. In contrast, the ein2 mutation did not suppress edr1-mediated resistance and associated phenotypes, indicating that ethylene and jasmonic acid-induced responses are not required for edr1 resistance. The EDR1 gene was isolated by positional cloning and was found to encode a putative MAP kinase kinase kinase similar to CTR1, a negative regulator of ethylene responses in Arabidopsis. Taken together, these data suggest that EDR1 functions at the top of a MAP kinase cascade that negatively regulates SA-inducible defense responses. Putative orthologs of EDR1 are present in monocots such as rice and barley, indicating that EDR1 may regulate defense responses in a wide range of crop species.
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PMID:Negative regulation of defense responses in plants by a conserved MAPKK kinase. 1115 43

Ethylene signaling in Arabidopsis begins at a family of five ethylene receptors that regulate activity of a downstream mitogen-activated protein kinase kinase kinase, CTR1. Triple and quadruple loss-of-function ethylene receptor mutants display a constitutive ethylene response phenotype, indicating they function as negative regulators in this pathway. No ethylene-related phenotype has been described for single loss-of-function receptor mutants, although it was reported that etr1 loss-of-function mutants display a growth defect limiting plant size. In actuality, this apparent growth defect results from enhanced responsiveness to ethylene; a phenotype manifested in all tissues tested. The phenotype displayed by etr1 loss-of-function mutants was rescued by treatment with an inhibitor of ethylene perception, indicating that it is ethylene dependent. Identification of an ethylene-dependent phenotype for a loss-of-function receptor mutant gave a unique opportunity for genetic and biochemical analysis of upstream events in ethylene signaling, including demonstration that the dominant ethylene-insensitive phenotype of etr2-1 is partially dependent on ETR1. This work demonstrates that mutational loss of the ethylene receptor ETR1 alters responsiveness to ethylene in Arabidopsis and that enhanced ethylene response in Arabidopsis not only results in increased sensitivity but exaggeration of response.
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PMID:Loss-of-function mutations in the ethylene receptor ETR1 cause enhanced sensitivity and exaggerated response to ethylene in Arabidopsis. 1217 68

In this work, four cDNA clones (Pd-ACS1,AJ890088; Pd-ETR1 and Pd-ERS1, AJ890092, AJ890091; and Pd-CTR1, AJ890089) encoding an ACC-synthase, two putative ethylene (ET) receptors, and a putative MAPKKK, respectively, were isolated and phylogenetically characterized in Prunus domestica L. subsp. insititia. Their expression was studied by real-time PCR during flower (closed, open and senescent) and fruit (early green, late green, maturation and ripening) development of damson plum, which is climateric. While two peaks of ET production were quantified at early green and ripening stages in whole fruits, the seed was not able to produce it during maturation and ripening stages. All studied genes were differentially expressed during flower and fruit development. In general, the level of transcripts of Pd-ACS1 was higher in fruits than in flowers. However, it was noteworthy that: (1) Pd-ACS1 expression was hardly detected in closed flowers and at low levels during early green stage; and fruit development provoked a notable differential expression in seeds, and pericarp; (2) the results of Pd-ACS1 expression during fruit development suggest a preponderant role of this gene from late green stage onward. The stamen was the only floral organ in which expression of both Pd-ETR1 and Pd-ERS1 receptor genes was not significantly altered during development; however, their expression decreased concomitantly with development of pistil (only floral organ to register a net ET production when fertilized) and during first days of ovary development (the highest ET production during all fruit development). Contrary to Pd-ERS1, the level of Pd-ETR1 mRNA was temporally quite similar in the seed. With regard Pd-ETR1, even its expression was very scarce during maturation of mesocarp, was stimulated during ripening. In the epicarp, Pd-ERS1 and Pd-ETR1 were low expressed during pit hardening increasing onward and decreasing during ripening. Pd-CTR1 expression was in the seed>mesocarp>>epicarp. Spatial and temporal levels of Pd-ACS1, Pd-ETR1, Pd-ERS1 and Pd-CTR1 mRNAs described in this work demonstrate that the expression of these genes is not always constitutive and that control of its transcription may play an important role in regulating the development of reproductive organs of damson plum.
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PMID:Stage- and tissue-expression of genes involved in the biosynthesis and signalling of ethylene in reproductive organs of damson plum (Prunus domestica L. subsp. insititia). 1741 34

Phosphatidic acid (PA) has only recently been identified as an important eukaryotic lipid-signalling molecule. In plants, PA formation is triggered by various biotic and abiotic stresses, including wounding, pathogen attack, drought, salinity, cold, and freezing. However, few molecular targets of PA have been identified so far. One of the best characterized is Raf-1, a mammalian MAPKKK. Arabidopsis thaliana CTR1 (constitutive triple response 1) is one of the plant homologues of Raf-1 and functions as a negative regulator of the ethylene signalling pathway. Here, it is shown that PA binds CTR1 and inhibits its kinase activity. Using different PA-binding assays, the kinase domain of CTR1 (CTR1-K) was found to bind PA directly. Addition of PA resulted in almost complete inhibition of CTR1 kinase activity and disrupted the intramolecular interaction between CTR1-K and the CTR1 N-terminal regulatory domain. Additionally, PA blocked the interaction of CTR1 with ETR1, one of the ethylene receptors. The basic amino acid motif shown to be required for PA binding in Raf-1 is conserved in CTR1-K. However, mutations in this motif did not affect either PA-binding or PA-dependent inhibition of CTR1 activity. Subsequent deletion analysis of CTR1's kinase domain revealed a novel PA-binding region at the C-terminus of the kinase.
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PMID:Phosphatidic acid binds to and inhibits the activity of Arabidopsis CTR1. 1800 17

The signal transduction pathway of the plant stress and defense hormone, ethylene, has been extensively elucidated using the plant genetic model Arabidopsis over the last two decades. Among others, a MAPKKK CTR1 was identified as a negative regulator that has led to the speculation of MAPK involvement in ethylene signaling. However, it remained unclear how the MAPK modules acting downstream of the receptors to mediate ethylene signaling. We have recently presented new evidence that the MKK9-MPK3/6 modules identified by combined functional genomic and genetic screens mediate ethylene signaling, which is negatively regulated by the genetically identified CTR1-dependent cascades. Our genetic studies show consistently that the MKK9-MPK3/MPK6 modules act downstream of the ethylene receptors. Biochemical and transgenic analyses further demonstrated that the positive-acting and negative-acting MAPK activities are integrated and act simultaneously to control the key transcription factor EIN3 through dual phosphorylations to regulate the EIN3 protein stability and downstream transcription cascades. This study has revealed a novel molecular mechanism that defines the specificity of complex MAPK signaling. Comprehensive elucidation of MAPK cascades and the underlying molecular mechanisms would provide more precise explanations for how plant cells utilize MAPK cascades to control specific downstream outputs in response to distinct stimuli.
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PMID:MAPK signaling in plant hormone ethylene signal transduction. 1970 18