Genetic Analysis of Natural Variation inAntirrhinumScent Profiles Identifies BENZOIC ACID CARBOXYMETHYL TRANSFERASE As the MajorLocusControlling Methyl Benzoate Synthesis.
TheAntirrhinumgenus has a considerable complexity in the scent profiles produced by different species. We have analyzed the genetic differences betweenA. majusandA. linkianum, 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 twolociwith simple or epistatic interactions. Several lines lacked methyl benzoate, a major Volatile Organic Compound emitted byA. majusbut missing inA. linkianum. Using a candidate gene approach, we found that theBENZOIC ACID CARBOXYMETHYL TRANSFERASEfromA. linkianumappeared 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 inA. linkianumas compared toA. majus. However, it showed multiple polymorphisms in the 5' promoter region including two insertions, one harboring anIDLEMITE transposon with additional sequences with high homology to thePLENA locusand a second one with somewhat lower homology to the regulatory region of theVENOSA locus. It also had a 778 bp deletion as compared to theA. majus BAMTpromoter region. Our results show that the differences in scent emission betweenA. majusandA. linkianummay 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.
Genetics, Instituto de Biotecnología Vegetal, Universidad Politécnica de Cartagena Cartagena, Spain.
Victoria
V
Ruiz-Hernández
Genetics, Instituto de Biotecnología Vegetal, Universidad Politécnica de Cartagena Cartagena, Spain.
Benjamin
B
Hermans
Genetics, Instituto de Biotecnología Vegetal, Universidad Politécnica de Cartagena Cartagena, Spain.
Julia
J
Weiss
Genetics, Instituto de Biotecnología Vegetal, Universidad Politécnica de Cartagena Cartagena, Spain.
Marcos
M
Egea-Cortines
IDLE MITE; acetophenone; floral scent; methyl benzoate; methyl cinnamate; recombinant inbred lines; transposable element; β-ocimene