The lack of floral synthesis and emission of isoeugenol in Petunia axillaris subsp. parodii is due to a mutation in the isoeugenol synthase gene

Abstract

SUMMARYFloral scent has been extensively investigated in plants of the South American genus Petunia. Flowers of Petunia integrifolia emit mostly benzaldehyde, while flowers of Petunia axillaris subsp. axillaris emit a mixture of volatile benzenoid and phenylpropanoid compounds that include isoeugenol and eugenol. Flowers of the artificial hybrid Petunia hybrida, a cross between P. integrifolia and P. axillaris, emit a similar spectrum of volatiles as P. axillaris subsp. axillaris. However, the flowers of P. axillaris subsp. parodii emit neither isoeugenol nor eugenol but contain high levels of dihydroconiferyl acetate in the petals, the main scentsynthesizing and scent-emitting organs. We recently showed that both isoeugenol and eugenol in P. hybrida are biosynthesized from coniferyl acetate in reactions catalyzed by isoeugenol synthase (PhIGS1) and eugenol synthase (PhEGS1), respectively, via a quinone methide-like intermediate. Here we show that P. axillaris subsp. parodii has a functional EGS gene that is expressed in flowers, but its IGS gene contains a frame-shift mutation that renders it inactive. Despite the presence of active EGS enzyme in P. axillaris subsp. parodii, in the absence of IGS activity the coniferyl acetate substrate is converted by an as yet unknown enzyme to dihydroconiferyl acetate. By contrast, suppressing the expression of PhIGS1 in P. hybrida by RNA interference also leads to a decrease in isoeugenol biosynthesis, but instead of the accumulation of dihydroconiferyl acetate, the flowers synthesize higher levels of eugenol.

Multiple Biochemical and Morphological Factors Underlie the Production of Methylketones in Tomato Trichomes

“…The presence of two distinct enzymes that contribute to the production of the same compound in the same organ, and even in the same cell, is not unprecedented, and such functional redundancy was recently reported for eugenol biosynthesis in Clarkia (Koeduka et al, 2009). In the case of MKS1 and MKS2, however, genetic evidence for epistatic interactions between the two loci suggests that they do not act independently of each other and therefore raises some questions.…”

Unraveling the regulation of floral fragrance biosynthesis

“…However, different species, cultivars, and/or varieties of flowers may emit a comparable volatile profile in regard to identity of the chemical composition, but the levels of individual compounds can be drastically different. 13,18 Other than through selective mutations, 19 how does the flower achieve such a precise floral volatile array? In MD, the FVBP gene network is transcriptionally regulated in a concerted manner, 13 resulting in a specific floral volatile array.…”

The Small Subunit of Snapdragon Geranyl Diphosphate Synthase Modifies the Chain Length Specificity of Tobacco Geranylgeranyl Diphosphate Synthase in Planta

“…The binary vector pCAMBIA 1303 (http://www.cambia.org/daisy/cambia/ 585) was modified by replacing the cauliflower mosaic virus 35S promoter, gusA, and monomeric green fluorescent protein (bases 11,600 to 2564) with the Clarkia breweri LIS promoter (1038 bp) (Orlova et al, 2006;Koeduka et al, 2009) containing the introduced NcoI site at its 39 end. The coding region of snapdragon (Antirrhinum majus) Am GPPS.SSU of 891 bp in size was then inserted into the NcoI-PstI site of the modified binary vector (plasmid pEF1.LIS-AmGPPS.SSU).…”