Elucidating Scent and Color Variation in White and Pink-Flowered Hydrangea arborescens 'Annabelle' Through...

Area of Science:

• Plant Molecular Biology
• Biochemistry
• Genetics

Background:

• Floral color and scent are key ornamental traits.
• These traits are governed by complex metabolic and transcriptional processes.
• Understanding these mechanisms is crucial for ornamental plant breeding.

Purpose of the Study:

• To elucidate the molecular basis of color and scent differences in Hydrangea arborescens.
• To compare the white-flowered 'Annabelle' (An) and pink-flowered 'Pink Annabelle' (PA) varieties.
• To identify key genes and metabolic pathways involved in floral trait variation.

Main Methods:

• Comparative Gas Chromatography-Mass Spectrometry (GC-MS) for volatile organic compounds (VOCs).
• Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) for metabolomics.
• RNA sequencing (RNA-Seq) for transcriptomic analysis.

Main Results:

• 'PA' showed higher quantities of benzenoid and phenylpropanoid volatiles, contributing to a stronger scent.
• 'PA' exhibited enriched phenylpropanoid biosynthesis pathways and differential expression of key biosynthetic genes (e.g., PAL, 4CL, CHS, DFR, ANS).
• Specific transcription factors (MYB, bHLH, ERF, WRKY) were identified as regulators of color and fragrance pathways.

Conclusions:

• 'PA' achieves enhanced color and aroma through synchronized transcriptional regulation of phenylpropanoid and flavonoid pathways.
• Metabolomic and transcriptomic data integration reveals coordinated activation of floral trait pathways.
• Findings provide molecular insights into the genetic and metabolic control of floral characteristics in Hydrangea.