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

Abstract

The Antirrhinum genus has a considerable complexity in the scent profiles produced by different species. We have analyzed the genetic differences between A. majus and A. 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 two loci with simple or epistatic interactions. Several lines lacked methyl benzoate, a major Volatile Organic Compound emitted by A. majus but missing in A. linkianum. Using a candidate gene approach, we found that the BENZOIC ACID CARBOXYMETHYL TRANSFERASE from A. linkianum 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 A. linkianum as compared to A. majus. However, it showed multiple polymorphisms in the 5′ promoter region including two insertions, one harboring an IDLE MITE transposon with additional sequences with high homology to the PLENA locus and a second one with somewhat lower homology to the regulatory region of the VENOSA locus. It also had a 778 bp deletion as compared to the A. majus BAMT promoter region. Our results show that the differences in scent emission between A. majus and A. linkianum 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.

A comparison of semi-quantitative methods suitable for establishing volatile profiles

“…An appropriate quantification of compounds ideally requires the use of a specific standard for each compound present in the sample [ 12 , 13 ]. Considering that plant VOCs may be present in dozens, their quantifications based on the inclusion of standards for each VOC increases the economic costs considerably [ 14 ].…”

A Proposed Methodology to Analyze Plant Growth and Movement from Phenomics Data

“…In this work we present a set of experiments using different plant materials, growth conditions and developmental stages in order to come up with a general procedure to analyze plant growth using phenomics-generated images. Four types of plants with different growth habits have been analyzed: Antirrhinum with a spike inflorescence, represented by A. majus, an erect plant, A. linkianum, a trailing plant showing low negative gravitropism in the shoot [35], petunia with a typical cymose inflorescence and strawberries forming a rosette. We used linear, polynomial, exponential, logarithmic and GAM fittings to identify the growth habit and movement in these plants.…”

“…Four different species were used with different growth habits. The Antirrhinum species A. majus and A. linkianum have a classic spike inflorescence but differ in the erect habit of A. majus and trailing growth habit of A. linkianum [35]. Petunia x hybrida is a Solanaceae close to tomato with a sympodial inflorescence [36,37].…”

“…The inbred line from Antirrhinum majus 165E and the wild species A. linkianum [35,39] were used. Petunia experiments were performed with the double haploid Petunia x hybrida W115 Mitchell [40].…”

The Snapdragon LATE ELONGATED HYPOCOTYL Plays A Dual Role in Activating Floral Growth and Scent Emission

“…Non-transgenic plants and plants belonging to T2 generations were sampled. Three or four flowers per line from 2 to 3 days post anthesis were used as described previously [47]. We collected volatiles starting at ZT3, for a period of 6 h during 24 h. All plants were acclimated to 12 h light/12 h dark (12LD) and 18/23 ºC cycle.…”