Transcriptome analysis of enzyme activities regulating ROS metabolism in olive (Olea europaea L.) reproductive tissues

Abstract

Transcriptome analysis of the olive stigma and pollen grain was carried out at different developmental stages and during in vitro pollen germination, respectively. Isolated mRNA was used to build cDNA libraries, which were subjected to 454+ sequencing. Readings were combined with sequences obtained from subtractive libraries, in order to produce a de novo assembly of the olive reproductive transcriptome. The presence of transcripts corresponding to major enzymes regulating ROS metabolism was assessed. Sequences corresponding to catalases, superoxide dismutase, dehydroascorbate reductase, GSNO reductase, NADPH oxidase, lipoxygenase and thioredoxins were retrieved and analysed using basic descriptive tools. Expression of transcripts in pollen and pistil was analysed by semiquantitative RT-PCR. Cellular localization of several enzymes was also carried out by using immunocytochemistry. We discuss how these enzyme activities may be involved in the olive pollen metabolism through germination, in the olive stigma over the periods before, after and during receptivity, and how they may contribute to the interaction pollen-stigma.