Front Plant Sci. 2016 Apr 13;7:462. doi: 10.3389/fpls.2016.00462. eCollection 2016.
- 1Department of Biology, University of Washington, Seattle WA, USA.
Abstract
To
successfully recruit pollinators, plants often release attractive
floral scents at specific times of day to coincide with pollinator
foraging. This timing of scent emission is thought to be evolutionarily
beneficial to maximize resource efficiency while attracting only useful
pollinators. Temporal regulation of scent emission is tied to the
activity of the specific metabolic pathways responsible for scent
production. Although floral volatile profiling in various plants
indicated a contribution by the circadian clock, the mechanisms by which
the circadian clock regulates timing of floral scent emission remained
elusive. Recent studies using two species in the Solanaceae family
provided initial insight into molecular clock regulation of scent
emission timing. In Petunia
hybrida, the floral volatile benzenoid/phenylpropanoid (FVBP) pathway
is the major metabolic pathway that produces floral volatiles. Three
MYB-type transcription factors, ODORANT 1 (ODO1), EMISSION OF BENZENOIDS
I (EOBI), and EOBII, all of which show diurnal rhythms in mRNA
expression, act as positive regulators for several enzyme genes in the
FVBP pathway. Recently, in P. hybrida and Nicotiana attenuata, homologs
of the Arabidopsis clock gene LATE ELONGATED HYPOCOTYL (LHY) have been
shown to have a similar role in the circadian clock in these plants, and
to also determine the timing of scent emission. In addition, in P.
hybrida, PhLHY directly represses ODO1 and several enzyme genes in the
FVBP pathway during the morning as an important negative regulator of
scent emission. These findings facilitate our understanding of the
relationship between a molecular timekeeper and the timing of scent
emission, which may influence reproductive success.
KEYWORDS:
Solanaceae; circadian clock; floral volatile; metabolic pathway; petunia; pollinator; tobacco
