A basic helix-loop-helix transcription factor, PhFBH4, regulates flower senescence by modulating ethylene biosynthesis pathway in petunia

Abstract

The basic helix-loop-helix (bHLH) transcription factors (TFs) play important roles in regulating multiple biological processes in plants. However, there are few reports about the function of bHLHs in flower senescence. In this study, a bHLH TF, PhFBH4, was found to be dramatically upregulated during flower senescence. Transcription of PhFBH4 is induced by plant hormones and abiotic stress treatments. Silencing of PhFBH4 using virus-induced gene silencing or an antisense approach extended flower longevity, while transgenic petunia flowers with an overexpression construct showed a reduction in flower lifespan. Abundance of transcripts of senescence-related genes (SAG12, SAG29) was significantly changed in petunia PhFBH4 transgenic flowers. Furthermore, silencing or overexpression of PhFBH4 reduced or increased, respectively, transcript abundances of important ethylene biosynthesis-related genes, ACS1 and ACO1, thereby influencing ethylene production. An electrophoretic mobility shift assay showed that the PhFBH4 protein physically interacted with the G-box cis-element in the promoter of ACS1, suggesting that ACS1 was a direct target of the PhFBH4 protein. In addition, ectopic expression of this gene altered plant development including plant height, internode length, and size of leaves and flowers, accompanied by alteration of transcript abundance of the gibberellin biosynthesis-related gene GA2OX3. Our results indicate that PhFBH4 plays an important role in regulating plant growth and development through modulating the ethylene biosynthesis pathway.

Ethylene Role in Plant Growth, Development and Senescence: Interaction with Other Phytohormones

“…Thus, RhHB1 mediates the antagonistic effect of GAs on ABA and ethylene during rose petal senescence, and the induction of petal senescence by ABA or ethylene operates through a RhHB1-RhGA20ox1 regulatory checkpoint. Another recent study suggests that a reduction in the bioactive GA content enhances the ethylene-mediated flower senescence (Yin et al, 2015). In this study, the overexpression of a basic helix-loop-helix ( bHLH ) transcription factor, PhFBH4 , increased the abundance of transcripts of ethylene biosynthesis genes and also increased ethylene production.…”

“…In this study, the overexpression of a basic helix-loop-helix ( bHLH ) transcription factor, PhFBH4 , increased the abundance of transcripts of ethylene biosynthesis genes and also increased ethylene production. Moreover, the increased expression of the GA metabolic gene GA2ox3 in PhFBH4-OX transgenic plants would raise bioactive GAs content, while silencing PhFBH4 would reduce their levels (Yin et al, 2015). Another study reported that the transcriptome changes associated with delayed flower senescence on transgenic petunia by inducing the expression of etr1-1 , down-regulated genes involved in gibberellin biosynthesis, response to gibberellins stimulus, and ethylene biosynthesis, at different time points (Wang H. et al, 2013).…”

The regulatory module MdPUB29‐MdbHLH3 connects ethylene biosynthesis with fruit quality in apple

“…bHLH TFs have been identified as key regulators in controlling anthocyanin biosynthesis in various plant species (Jaakola, 2013). In addition to their function in mediating pigment formation, some of these bHLH TFs can also influence ethylene biosynthesis by activating the expression of ACO or ACS genes (Yin et al, 2015;Li et al, 2017;Alessio et al, 2018), suggesting their vital roles in the regulation of ethylene biosynthesis.…”

Spatial and temporal transcriptome changes occurring during flower opening and senescence of the ephemeral hibiscus flower,Hibiscus rosa-sinensis

“…These include ETHYLENE INSENSITIVE3 (EIN3)-like genes in carnation ( Dianthus caryophyllus ; Iordachescu and Verlinden, 2005) and ETHYLENE-RESPONSIVE ELEMENT BINDING FACTORS (ERFs) in daffodils (Hunter et al , 2002) and petunia ( Petunia hybrida ; Liu et al , 2010). More recently, virus-induced gene silencing and overexpression studies have revealed a basic helix-loop-helix transcription factor, PhFBH4, that positively controls the timing of petunia flower senescence, likely by regulating induction of the ethylene biosynthetic pathway (Yin et al , 2015). …”