Abstract Detail



Reproductive Processes

Majetic, Cassie [1], Farragher, Bridget [2], Richmond, Alana [2].

Floral scent plasticity and associated scent gene expression patterns in wild-derived Petunia species in response to soil nitrogen conditions..

Many plants rely on floral scent to attract pollinators to spread their gametes. However, previous research suggests that levels of scent emission can be altered by environmental factors, indicating plasticity in floral scent that may lead to key pollinator behavior changes. In particular, soil nitrogen content has shown potential to impact production of benzenoid volatiles in hybrid Petunia (a floral scent model system), with emission rate of eugenol increasing with increasing soil nitrogen concentrations. We therefore hypothesized that this linear plastic relationship would also be found for three inbred lines of wild-derived P. axillaris, a species with strong benzenoid and phenylpropanoid scent emission. In contrast, we hypothesized that plastic responses of scent emission to soil nitrogen would be absent from three inbred lines of weakly-scented P. exserta. To test these hypotheses, plants from each line were exposed to one of three possible nitrogen treatments (no additional nitrogen, low (0.6 g nitrogen), or high (1.2 g nitrogen)) and scent emission rate of five benzenoid/phenylpropanoid compounds was determined using dynamic headspace extraction and gas chromatography/mass spectroscopy. MANOVA analysis of emission rate data provided partial support for our hypotheses. P. axillaris lines generally show greater plasticity of scent in response to soil nitrogen concentration than P. exserta lines, but a great deal of genetic variability is present in scent plasticity, with additional variability associated with the identity of the scent compound. However, scent emission in P. axillaris line generally and unexpectedly peaked with the low concentration of nitrogen treatment, with implications for the impacts that variable soil nutrient levels might have on pollinator behavior due to fluctuating scent profiles.  To further assess potential mechanisms for this variation in scent emission rate, we performed an initial examination of gene expression patterns for key floral scent pathway genes EMISSIONS OF BENZENOIDS II (EOBII) and ODORANT1 (ODO1). RNA was extracted from eighteen plants for reverse transcription and rtPCR, representing each experimental line-treatment combination. Comparison of normalized Cq values suggested that gene expression was highly variable among treatments in each P. axillaris and exserta line. Unexpectedly, for the majority of the plant lines, additional nitrogen down-regulated gene expression, even when scent emission rates were quite high. These contradictory patterns suggest that future research should explore other candidate genes for regulation of scent emissions in response to nitrogen, as well as regulation of volatilization of endogenous benzenoid pools as an alternative mechanism for plasticity in this system.


1 - Saint Mary's College, Dept Of Biology, SR 933 North, Notre Dame, IN, 46556, United States
2 - Saint Mary's College, Department of Biology, State Route 933, Notre Dame, IN, 46556, USA

Keywords:
Petunia
Benzenoids
Phenylpropanoids
Floral Scent
Gene Expression
Plasticity
Soil Nitrogen.

Presentation Type: Oral Paper
Number: 0006
Abstract ID:233
Candidate for Awards:None


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