Emission of volatiles at advanced stages of flower development is a strategy used by plants to lure pollinators to the flower. We reveal that GA negatively regulates floral scent production in petunia. We used Agrobacterium-mediated transient expression of GA-20ox in petunia flowers and a virus-induced gene silencing approach to knock down DELLA expression, measured volatile emission, internal pool sizes and GA levels by GC-MS or LC–MS/MS, and analyzed transcript levels of scent-related phenylpropanoid-pathway genes. We show that GA has a negative effect on the concentrations of accumulated and emitted phenylpropanoid volatiles in petunia flowers; this effect is exerted through transcriptional/post-transcriptional downregulation of regulatory and biosynthetic scent-related genes. Both overexpression of GA20-ox, a GA-biosynthesis gene, and suppression of DELLA, a repressor of GA-signal transduction, corroborated GA's negative regulation of floral scent. We present a model in which GA-dependent timing of the sequential activation of different branches of the phenylpropanoid pathway during flower development may represent a link between the showy traits controlling pollinator attraction, namely color and scent.
Bibliographical noteFunding Information:
We thank Danziger ‘Dan’ Flower Farm for providing the plant material. We thank Drs Sun and Hu from Duke University for providing 35S:GFP–RGA, Drs Avni and Aloni from Tel-Aviv University for providing 35S:GA20-ox–GFP and Drs Huberman, Riov and Goren from The Hebrew University of Jerusalem for providing CPAS. This work was funded by Israel Science Foundation grant 247/14. A.V. is an incumbent of the Wolfson Chair in Floriculture.
© 2017 The Authors. New Phytologist © 2017 New Phytologist Trust
- floral scent
- showy trait