Two showy traits, scent emission and pigmentation, are finely coregulated by the MYB transcription factor PH4 in petunia flowers

Abstract

The mechanism underlying the emission of phenylpropanoid volatiles is poorly understood. Here, we reveal the involvement of PH4, a petunia MYB-R2R3 transcription factor previously studied for its role in vacuolar acidification, in floral volatile emission. We used the virus-induced gene silencing (VIGS) approach to knock down PH4 expression in petunia, measured volatile emission and internal pool sizes by GC-MS, and analyzed transcript abundances of scent-related phenylpropanoid genes in flowers. Silencing of PH4 resulted in a marked decrease in floral phenylpropanoid volatile emission, with a concurrent increase in internal pool levels. Expression of scent-related phenylpropanoid genes was not affected. To identify putative scent-related targets of PH4, we silenced PH5, a tonoplast-localized H(+) -ATPase that maintains vacuolar pH homeostasis. Suppression of PH5 did not yield the reduced-emission phenotype, suggesting that PH4 does not operate in the context of floral scent through regulation of vacuolar pH. We conclude that PH4 is a key floral regulator that integrates volatile production and emission processes and interconnects two essential floral traits - color and scent.

CCoAOMT Down-Regulation Activates Anthocyanin Biosynthesis in Petunia

“…Interestingly, emission of eugenol was not significantly lower in the ir-PhCCoAOMT1 lines, similar to the results obtained when EMISSION OF BENZENOIDS I was silenced (Spitzer-Rimon et al, 2012). This can be explained by an active emission process that lowers internal pools of eugenol while sustaining its emission level in petunia petals (Cna'ani et al, 2015;Widhalm et al, 2015).…”

“…Previous studies revealed that two R2R3-MYB transcription factors, ANTHOCYANIN2 (AN2) and ODORANT1 (ODO1), drive anthocyanin and volatile phenylpropanoid biosynthesis, respectively (Hoballah et al, 2007;Klahre et al, 2011). Interestingly, only a few studies have focused on interactions between phenylpropene and anthocyanin pathways in petunia (Verdonk et al, 2005;Ben Zvi et al, 2008;Cna'ani et al, 2015), leaving an open question about the carbon flux distribution between these two biosynthetic pathways and their coregulation.…”

“…color and scent between petunia cultivars suggest that anthocyanin and phenylpropene pathways are closely regulated (Cna'ani et al, 2015). Previous studies revealed that two R2R3-MYB transcription factors, ANTHOCYANIN2 (AN2) and ODORANT1 (ODO1), drive anthocyanin and volatile phenylpropanoid biosynthesis, respectively (Hoballah et al, 2007;Klahre et al, 2011).…”

PhERF6, interacting with EOBI, negatively regulates fragrance biosynthesis in petunia flowers

“…Previous studies showed that the transcription factors involved in floral scent are mainly R2R3 MYB transcription factors, such as ODO1, EOBI, EOBII, PhMYB4 and PH4 (Colquhoun et al ., ; Spitzer‐Rimon et al ., ; Cna'Ani et al ., ), and here we identified PhERF6, a member of ERF family, as a novel type of transcription factor involved in floral scent. According to the experimental data provided in this study, we suggested a model to explain the involvement of PhERF6 in the FVBP biosynthesis pathway (Fig.…”

The circadian clock contributes to diurnal patterns of plant indirect defense in nature

“…In plants, the flux of isoprenoids, to which sesquiterpenes belong, is known to be controlled both by the clock and by light (Dudareva et al ; Pokhilko et al ). Furthermore, plant volatiles need to cross membranes and the cuticle, or exit through stomata to be emitted, which means the regulation of plant volatile emission can be divided between production and release steps (Cna'ani et al ; Widhalm et al ). Each step of volatile emission, including stomatal opening and metabolic transport processes, may be differently affected by the circadian clock.…”