Ph.D Thesis

Ph.D StudentYariv Yoela
SubjectThe Isolation and Characterization of Fruit Ripening-related
Genes in Melon (Cucumis melo L.)- a Genomic
DepartmentDepartment of Biology
Supervisors PROF. Gadi Schuster
PROF. Nurit Katzir
PROF. Ron Pinter
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Melon (Cucumis melo L.), of the Cucrbitaceae family, is an important crop that includes a wide range of wild and cultivated varieties. Fruit quality is determined by a combination of traits, such as flavor, aroma, color, shape and duration of shelf life. These quality traits are affected by the biochemical and physiological changes that occur in the process of fruit ripening. These changes take place as a result of the conjoint, coordinated and controlled expression of a very large number of genes in the course of fruit ripening, and they determine fruit quality. The properties of the melon fruit are economically important nowadays, and there is an increasing demand for fruit with improved characteristics. The detection of genes filling important functions in melon ripening will enable the improvement of fruit quality in the future. So far, only few genes associated with melon maturation and ripening processes have been identified.

The objective of this study was detecting genes involved in melon maturation processes and in the determination of melon fruit properties, understanding their expression patterns and categorizing them into functional groups. An effective infrastructure was constructed in order to enable comprehensive detection of genes that are expressed uniquely in melon fruit. Genes expressed during the various stages of melon development and maturation and genes representing various fruit quality traits have been located.

In order to further explore the function of a gene that has been identified by the aforementioned infrastructure, we proceeded from the general case to individual ones, choosing a gene that was salient in its differential expression within the ripe melons. One such gene was found fully homologous with a clone isolated previously from melon; called pMel7, whose function has not yet been discovered. Its resemblance to other proteins shows that it shares an origin with three large protein families: PR-10, MLP and Bet V 1. No significant catalytic activity of members of the three families, nor of pMel7 in melon, has yet been identified, but various studies have presented clues suggesting its existence. Tests conducted within the frame of this study have shown that contrary to previous evidence in other fruits, pMel7 in melon does not manifest RNase or lipase enzymatic activity. In addition, we have shown its significant structural resemblance to plant allergens, and primary evidence that it constitutes an allergen in melon. However, it has a thus far unknown yet possibly important function in fruit ripening.