Molecular biology of Ethylene


Provide a detailed knowledge of ethylene physiology in plants, and its role in developmental processes with particular emphasis on these related to horticultural produce Analyze the processes and the mechanisms involved in ethylene biosynthesis, perception and signal transduction. Provide a general knowledge and information of the role of ethylene in processes such as leaf growth and development, and senescence and abscissionIdentify the role of ethylene under abiotic stress conditionsDescribe the role of ethylene in modulating  ripening  of fleshy fruit Describe the main processes, in particular at molecular level,  characterizing fruit ripening and relate them with the evolution of the extrinsic and intrinsic parameters used to monitor quality at harvest Describe the relationship between the gaseous hormone and the expression of ripening-related genes (ethylene-dependent and ethylene-independent pathways). Provide specific and detailed information about the pathways of both primary and secondary metabolic ripening-related processes and describe  the effects of ethylene and its inhibitors on the regulation of these pathways


 Biochemistry, Plant Physiology, Plant Molecular biology,  Cell and Molecular Biology, Molecular biology techniques, Principles of Horticulturae

Learning Outcomes

After completing the unit, students will be able to:   Describe the role of ethylene in plants and the main hormonal cross-talk  Define the different processes occurring in plant tissues concerning ethylene biosynthesis, perception and signal trasnduction Analyze and evaluate  the different processes characterizing horticultural plants in which ethylene plays a major roleDefine the phyisiological role of ethylene in climacteric and non-climacteri fruit ripening Relate the quality parameters of fruit at harvest  to the underlying molecular and biochemical mechanisms Support and understand  decisions concerning horticultural production and agronomical practices affecting ethylene phsyology Identify and judge the critical points in quality management of different fruit commodities Demonstrate their ability in evaluating ripening-related technical and  scientific issues Apply their knowledge to formulate hypotheses and set up applied research protocols in the field of horticultural science Communicate with appropriate descriptions and terms the specific issues and subject matters described in the unit.  


 Molecular Biology of Ethylene  course contents. Ethylene is the gaseous plant hormone and it is involved in controlling events throughout the life cycle of plants. This growth regulator plays important roles in several processes, such as seed germination, tissue (roots and shoots) growth, cell separation, senescence, plant-pathogen interactions, and fruit ripening. A bulk of information is now available concerning processes and regulatory mechanisms related to the biosynthesis of the hormone, the receptors effective in binding ethylene, and several steps of the transduction system. Although most of the dicoversies have been obtained using the model species Arabidopsis and its mutants,  important advancements in andesting the role of the gaseous hormone have been the result of specific studies carried out in crop plants (including horticultural plants) concerning key events such as senescence and absission. In addition , considering the role played by ethylene in fruit ripening, tomato has been identified as the model species for such studies. In climacteric fruit, ripening is  charcaterized by the increase in respiration and ethylene production.  Fruit ripening is a developmentally- and hormonally-regulated process that encompasses a wide range of cellular changes including fruit softening, chlorophyll degradation, pigment production, aroma development etc.  A detailed knowledge of the molecular regulation of both  the ethylene production and  perception mechanisms as well as the signal transduction pathways has allowed a better comprehension of the relationship between this hormone and the typical changes occurring in ripening fruit.  This is particularly true in tomato, where the existence of a plethora of ripening mutants, detailed genetic maps and common transformation protocols have made this species the model system for genetic, molecular and biochemical studies of fruit ripening. Besides ethylene physiology, emphasis will be given to biochemical and molecular aspects of primary metabolic processes (respiration), cell wall  modifications, secondary metabolisms such as pigmentation changes and aroma compound production during ripening and in relation to different storage conditions affecting general metabolism (including ethylene physiology). Genomics and system biology approaches will be described and results, in a context of  a comparative approach, discussed and analyzed to identify common and divergent key molecular components of the ripening syndrome in climacteric and non-climacteric species.

Content Delivery

Considering the background (see prerequisites) of the students attending the Unit and the topics of the Unit, the delivery of the component will be done through lectures as a typical University course Power point presentations will be used. The Unit will be divided in 3 different modules: Module 1- Introduction. Ethylene as the gaseous plant hormone: the hormone biosynthesis and the signalling pathways. Module 2:  The role of ethylene in plant processes affecting  yield and productivity, with particular emphasis on leaf senescence and fruit abscission in horticultural plants. Modul e3.   Fruit ripening as a genetically-regulated syndrome and the biology  of ethylene in climacteric fruit.  Primary and secondary metabolisms and the changes occurring during fruit ripening, considering in particular ethylene-dependent and ethylene-independent processes.  All these aspects will be discussed mostly at biochemical and molecular level, but with strong links also to practical aspects.

Coursework And Assignment Details

The assignment of this unit will be and  Individual written examination  that will consist of two parts: A) Multiple choice and B) essay.   A)   Multiple choice (40%). Students will be asked to answer  up to 15 specific questions or statements concerning topics discussed during the week course B)   Essay (60%). Students will appropriately describe and analyze a specific ripening-related process discussed during the week course   Assessment criteria - Appropriate scientific language and description of the biochemical and molecular events characterizing the specific process -  Demonstration of a detailed and broad knowledge of the process in a general view of the ripening syndrome and the storage procedures.