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,2019-01-18,#,Abstract,Ethylene is a gaseous plant hormone involved in several important physiological processes throughout a plants life cycle,.,Decades of scientific research devoted to deciphering how plants are able to sense and respond to this key molecule have culminated in the establishment of one of the best characterized signal transduction pathways in plants.,The ethylene signaling pathway starts with the perception of this gaseous hormone by a family of membrane-anchored receptors followed by a Raf-like kinase CTR1 that is physically associated with the receptors and actively inhibits downstream components of the pathway.,A major gap is represented by the mysterious plant protein,EIN2,that,genetically works downstream of CTR1 and upstream of the key transcription factor,EIN3,.,Transcriptional regulation by EIN3 and EIN3-family members has emerged as a key aspect of ethylene responses.,The major components of this transcriptional cascade have been characterized and the involvement of post-transcriptional control by ubiquitination has been determined.Nevertheless,many aspects of this pathway still remain unknown.,Recent genomic studies aiming to provide a more comprehensive view of modulation of gene expression have further emphasized the ample role of ethylene in a myriad of cellular processes and particularly in its crosstalk with other important plant hormones.,This review aims to serve as a guide to the main scientific discoveries that have shaped the field of ethylene biology in the recent years,AbstractEthylene is a gaseous,1,EFFECTS OF ETHYLENE,Fruit,Ripening,Abscission,;leaf flower fruits(thinning,harvesting),Hook Closure Maintenance,Initiates Germination in Grains,Activates dormant buds(potatoes in storage),Stem elongation in deep-water rice,Induces Flowering in Pineapple,Promotes Female Expression in Flowers,Flower and Leaf Senescence:Ag preventative(vase life),Ethylene,EFFECTS OF ETHYLENEEthylene,2,1.Introduction,Hormones act as chemical messengers in the control of the,molecular,biochemical,and physiological,events underlying growth and development.,Hormones also serve as,essential integrators of developmental programs with the environmental signals,.A basic challenge in biology is,therefore,to understand the molecular mechanisms that underlie hormone action,in other words,how those chemical signals are sensed by and communicated within the cells to trigger the relevant responses,.,This process can be divided into three main steps:,(1)signal perception,(2)signal transduction or a cascade of biochemical events that ultimately leads to the induction of the final step,(3)the response.,Among the plant hormones,ethylene distinguishes itself by its simple hydrocarbon chemical structure(C2H4)and its gaseous nature.This simple molecule,however,plays a major role in plant growth and development by influencing a wide range of complex physiological processes throughout the entire plant life cycle,from seed germination to flowering,fruitripening,and senescence,1.Introduction Hormones act,3,One of the most dramatic effects of ethylene on plant morphogenesis is the classical triple response exhibited by dark-grown seedlings exposed to ethylene.The triple response in Arabidopsis is characterized by(1),exaggerated curvature of the apical hook,(2),radial swelling of the hypocotyl,and(3),inhibition of hypocotyl and root growth,Fig.1 Phenotypes of dark-grown three-day-old seedlings of,Arabidopsis thaliana.The plant on the left was grown without hormonal supplementation,whereas the plant on the right was exposed to 10,m,M ethylene precursor ACC and thus shows a typical triple response.,A,series of elegant genetic,molecular,and biochemical studies,are uncovering a largely,linear pathway that transduces the ethylene signal from the,endoplasmic reticulum membrane to the nucleus,Fig.2 The ethylene signaling pathway and its genetically characterized components.The signaling pathway components are shown in their sequential order of action.Components drawn in white represent active forms,whereas gray ovals represent their inactive versions.Binding of ethylene to the receptors,represented by ETR1,leads to activation of ethylene responses.Dotted oval represents EIN3 degradation by the 26S proteasome pathway due to action of EBF1 and EBF2.Arrows indicate activation steps,whereas a blocked arrow depicts repression of downstream elements by CTR1.,This review aims to,summarize the current state of knowledge in the ethylene field,.We will start with the description of the main experimental breakthroughs that resulted in the discovery of the known ethylene signaling components to then describe the,genomic approaches employed to characterize the molecular aspects of the ethylene response.,One of the most dramatic eff,4,2.Ethylene perception is mediated by a small family of receptors,The development of modern molecular genetic approaches and the selection of,Arabidopsis as a plant,model system,opened a new door not only f
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