Genetic Analysis of Natural Variation in Scent Profiles Identifies BENZOIC ACID CARBOXYMETHYL TRANSFERASE As the Major Controlling Methyl Benzoate Synthesis

The genus has a considerable complexity in the scent profiles produced by different species. We have analyzed the genetic differences between and , two species divergent in the emission of methyl benzoate, methyl cinnamate, acetophenone, and ocimene. The genetic analysis showed that all compounds segregated in a Mendelian fashion attributable to one or two with simple or epistatic interactions. Several lines lacked methyl benzoate, a major Volatile Organic Compound emitted by but missing in . Using a candidate gene approach, we found that the from appeared to be a null allele as we could not detect mRNA expression. The coding region did not show significant differences that could explain the loss of expression. The intron-exon boundaries was also conserved indicating that there is no alternative splicing in as compared to . However, it showed multiple polymorphisms in the 5' promoter region including two insertions, one harboring an MITE transposon with additional sequences with high homology to the and a second one with somewhat lower homology to the regulatory region of the . It also had a 778 bp deletion as compared to the promoter region. Our results show that the differences in scent emission between and may be traced back to single genes involved in discrete biosynthetic reactions such as benzoic acid methylation. Thus, natural variation of this complex trait maybe the result of combinations of wild type, and loss of function alleles in different genes involved in discrete VOCs biosynthesis. Furthermore, the presence of active transposable elements in the genus may account for rapid evolution and instability, raising the possibility of adaptation to local pollinators.