Genomic Analysis of the Upstream Sequences of Limonene Synthase Genes in Sweet Orange

Genomes from Citrus clementina (clementine mandarin) and Citrus sinensis (sweet orange) were recently made available for the community. In addition to that another sequence of the sweet orange genome, which was assembled in chromosomes, was released allowing a deeper evaluation of the genus.

An important focus of our work is the biosynthesis of essential oil in citrus. We had already done analysis of yield and quality of essential oils extracted from the flavedo of citrus fruits in different developmental stages together with expression analysis of some terpene synthase genes, including two limonene synthases that showed different expression patterns. We then decided to carry a genomic analysis of these genes and used the genomes available. After rounds of blast analysis we came out with more than eighty putative terpene synthase gene sequences. These were filtered and got those encoding limonene synthases for a total of eight different complete coding sequences. We isolated the 2 Kb fragment upstream of them when we verified that two were not complete and therefore they were not used furthermore. Comparison of these upstream sequences reveals that they are not very similar and evaluation for presence of plant regulatory sequences with TSSP/Prediction of PLANT Promoters (Using RegSite Plant DB, Softberry Inc.) showed a different distribution of the regulatory elements in the sequences. This result could explain the different gene expression pattern verified before for two different limonene synthases.

Financial support: FAPESP (08/57909-2), and CNPq (573848/08-4 and 475339/2011-8).