Regulation of Methylbenzoate Emission after Pollination in Snapdragon and Petunia Flowers

Abstract

The molecular mechanisms responsible for postpollination changes in floral scent emission were investigated in snapdragon cv Maryland True Pink and petunia cv Mitchell flowers using a volatile ester, methylbenzoate, one of the major scent compounds emitted by these flowers, as an example. In both species, a 70 to 75% pollination-induced decrease in methylbenzoate emission begins only after pollen tubes reach the ovary, a process that takes between 35 and 40 h in snapdragon and ‫ف‬ 32 h in petunia. This postpollination decrease in emission is not triggered by pollen deposition on the stigma. Petunia and snapdragon both synthesize methylbenzoate from benzoic acid and S -adenosyl-L -methionine (SAM); however, they use different mechanisms to downregulate its production after pollination. In petunia, expression of the gene responsible for methylbenzoate synthesis is suppressed by ethylene. In snapdragon, the decrease in methylbenzoate emission is the result of a decrease in both S -adenosyl-L -methionine:benzoic acid carboxyl methyltransferase (BAMT) activity and the ratio of SAM to S -adenosyl-L -homocysteine ("methylation index") after pollination, although the BAMT gene also is sensitive to ethylene.

The composition and timing of flower odour emission by wild Petunia axillaris coincide with the antennal perception and nocturnal activity of the pollinator Manduca sexta

“…and accessions. Rhythmic emissions of methyl benzoate, benzaldehyde, isoeugenol, benzeneacetaldehyde and benzyl benzoate have also been detected in Petunia hybrida (Kolosova et al 2001;Verdonk et al 2003;Negre et al 2003). The non-rhythmic emission of hexadecadienal methyl ester and Z-9,17-octadecadienol (Fig.…”

“…A shortened period of volatile production probably serves to save energy and resources. Soon after pollination, the production of methyl benzoate, benzaldehyde and benzeneacetaldehyde decreases in Petunia (Negre et al 2003), another indication of a strategy to reduce costs of volatile production. The production of flower volatiles restricted to the night could also be an adaptation of the plant to avoid seed predators, as was shown by Baldwin et al (1997) for N. attenuata.…”

ODORANT1Regulates Fragrance Biosynthesis in Petunia Flowers

“…The expression pattern of ODO1, as determined by RNA gel blot analyses, displays all characteristics predicted from a scent regulator. First, it is only expressed in the tube and limb of the petals ( Figure 1C), the two tissues responsible for scent production (Verdonk et al, 2003), which specifically express BSMT and BPBT (Negre et al, 2003;Boatright et al, 2004). Second, its increase in transcript levels precedes the emission of volatile benzenoids ( Figures 1A and 1B).…”

“…These volatile benzenoids are mostly produced by the petals (Verdonk et al, 2003), and emission decreases upon pollination (i.e., when the pollen tubes reach the base of the style). This communication between the various flower organs is mediated by ethylene (Negre et al, 2003).…”

“…Only two corresponding cDNAs have been identified from petunia petals, S-adenosyl-L-Met:benzoic acid carboxyl methyltransferase (BSMT) and benzoyl-CoA:benzyl alcohol/phenylethanol benzoyltransferase (BPBT) (Negre et al, 2003;Boatright et al, 2004). The steady state transcript levels of petunia BPBT change rhythmically and peak in the afternoon, preceding the peak levels of its product benzylbenzoate (Boatright et al, 2004).…”