Análise de sequências de genes de limoneno sintases em genomas de citros

Abstract

Limonene, a terpene found in essential oil extracted from citrus peel, has great applicability on industry. Is it known that there are great limonene concentration differences among citrus varieties, however, limonene remains the principal component of essential oils from this group. In this study, it was hypothesized that genomic differences could be related to the variations of limonene observed between different species. In order to prove this, an in silico analysis was performed and limonene synthase sequences were searched on Citrus sinensis variety “Valencia” genome, available on “Citrus Genome Database”. Those results were used to obtain highly similar sequences from species such as C. sinensis (sweet orange “Ridge Pineapple”), C. reticulata (tangerine), C. ichangensis (papeda), C. maxima (pomelo) and C. medica (cider). Results indicate that there are thirteen gene sequences coding for limonene synthases in Valencia. Those thirteen sequences were aligned. The results of the alignments served to have an initial idea ofthe real similarity between the sequences, we see that there are conserved regions in several of the alignments performed, which implies that the varieties have phylogenetic relationships, which is expected since they all belong to the same genus. At no time, the sequences were 100% identical, which shows an interesting result, after all, studies have proven that different varieties/species have different amounts of limonene in their essential oils. There is high sequence similarity among the sweet oranges, C. maxima and C. reticulate, which confirms the ancestral origin of those varieties, since C. sinensis is a hybrid among C. maxima, C. reticulata and another unknown citrus species. Another analysis that was performed was a sequence similarity search using the translated sequence from the thirteen limonene synthase proteins from Valencia against the same varieties used on genomic similarity search. This analysis resulted the same pattern of similarity among C. sinensis, C. maxima and C. reticulate found on genomic similarity results, and the phylogenetic analysis confirmed those results. The analysis of the promoter region did not show the similarities found in the analysis of gene and protein sequences, which may be the expected result, these differences between promoters may be related to the regulation of genes and thereby explain the difference in limonene synthases between species and variety of citrus. Although eukaryotic promoter analysis is one of the most difficult computation problems, an in-depth study of the referred promoter regions is needed to elucidate our interpretation of genomic and proteomic comparisons.