Shaltiel-Harpaz - Migal Galilee Research Institute, Kiryat Shmona , Israel
H. Reuveny - Migal Galilee Research Institute, Kiryat Shmona , Israel
Almond (Prunus dulcis) (Mill.) D.A.Webb is an agriculturally and economically important fruit tree from the Rosaceae family extensively used in the food industry. The monoterpenes and sesquiterpenes perform important ecological functions such as insecticidal and antifeedant activities against various insects. In this study, biochemical bioinformatical and molecular methodologies were integrated to evaluate the differential accumulation of volatile terpenes from different organs of a diverse collection of almond varieties. The leaves, flowers and fruits of the almond varieties accumulate various terpene compounds among which geraniol is most abundant in leaves, while linalool is the dominant monoterpene in fruit tissue. To identify terpene synthases (TPSs) involved in the production of these volatile terpenes, existing genome databases of the Rosaceae were screened for almond genes with significant sequence similarity to plant TPSs. The bioinformatic analysis led to the identification of seven putative TPSs genes with complete open reading frames. Further, we characterized the enzymes encoded by these seven complementary DNAs using the heterologous E. coli system. All seven were found to be functional of which four monoterpene synthases; PdTPS1, PdTPS3, PdTPS5, and PdTPS6 belong to the TPS-b clade and catalyze the formation β-phellandrene, geraniol, linalool, and farnesene, respectively. The sesquiterpene synthases; PdTPS2 and PdTPS4 belonging to the TPS-a, catalyzes the formation of bergamotene as a major product while another sesquiterpene synthase, PdTPS7 from TPS-g clade showed nerolidol synthase activity. The qRT-PCR analysis revealed that the various tissues of almond varieties studied showed differential transcription for all these PdTPSs genes. The TPS genes described here and potential other TPS genes from P. dulcis may be developed into molecular markers to aid in breeding and improvement of cultivars with superior ecological functions such as repelling insects e.g. almond seed wasp, Eurytoma amygdali Enderlein, as is one of the major obstacles to efficient integrated pest management (IPM) in almond orchards. This is the first and foremost investigation from almonds which identified and characterized the TPSs functional diversity parallels the diversity of volatile emissions from different tissues and forms the basis for further understanding this chemical diversity at the molecular and mechanistic levels in almond.
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