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.
Highlights
Flower senescence is an important coordinated process regulated by internal and environmental changes.[1]
PhFBH4 is involved in flower senescence by modulating ethylene biosynthesis In this study, we identified a basic helix-loop-helix (bHLH) transcription factors (TFs), named PhFBH4 because of its sequence similarity to Arabidopsis FBH4
We found that its transcript abundance increased dramatically during flower senescence, and increased in response to a range of abiotic stressors and to treatments with plant hormones, ethylene
Summary
Flower senescence is an important coordinated process regulated by internal and environmental changes.[1]. Expression profiles of the ethylene-responsive element-binding factor (ERF) family genes were studied in detail.[3] Some of ERFs appear to be associated with fruit ripening and with corolla senescence.[4,5,6,7] Among the HB TFs upregulated in Arabidopsis petals was KNAT1, a member of the Class I KNOX family known to modulate cytokinin levels.[8] The expression of genes encoding AUX-IAA proteins in Arabidopsis suggests the role of auxin in petal senescence. Petunia plants in which bHLH expression was downregulated by VIGS or antisense silencing showed extended flower longevity while overexpression of the PhFBH4 in petunia resulted in earlier flower senescence. These data suggest an important role for PhFBH4 in the control of flower senescence
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