De novo assembly of the olive tree (Olea europaea L.) reproductive transcriptome

Abstract

Olive transcriptome has been recently built as the result of library screening through the use of different NGS strategies. Such transcriptome mainly relies on vegetative reads. However, the peculiarity of the reproductive tissues, and the widely reported presence of numerous tissue-specific transcripts in both stigma and pollen grains made us to attempt a similar approach in the later tissues. mRNA was isolated from olive stigmas and pollen grains at different developmental stages and during in vitro pollen germination, respectively. cDNA libraries were built from the isolated mRNA, and subjected to 454/Roche Titanium+ sequencing. Moreover, NGS readings were combined with additional sequences obtained from subtractive libraries, in order to produce a de novo assembly of the olive reproductive transcriptome. Several public software and other tools developed by authors were used for this purpose. Sequences were assembled together into 58 098 (stigma) and 26 422 (pollen) contigs, respectively. Functional annotation is currently underway, however numerous gene products have been previously analysed, particularly those corresponding to major enzymes regulating ROS metabolism. Some of them, including catalases, superoxide dismutase, dehydroascorbate reductase, GSNO reductase, NADPH oxidase, lipoxygenase and thioredoxins, have been further analysed using basic descriptive tools.