RNA-seq based transcriptomic analysis of CPPU treated grape berries and emission of volatile compounds

Area of Science:

• Plant Science
• Agricultural Chemistry
• Molecular Biology

Background:

• Grapevine (Vitis vinifera L.) is a globally significant fruit crop with numerous value-added products.
• Plant growth regulators, such as CPPU (forchlorfenuron), are used to enhance grape berry development.
• Understanding the molecular mechanisms behind CPPU's effects on grape berry composition is crucial for viticulture.

Purpose of the Study:

• To investigate the influence of CPPU (forchlorfenuron) on the berry development and volatile compound profiles of 'Shine Muscat' grapes.
• To identify differentially expressed genes (DEGs) and associated biosynthesis pathways affected by CPPU treatment using transcriptomic analysis.
• To elucidate the molecular basis of CPPU-induced changes in grape berry volatile metabolism.

Main Methods:

• Field application of varying CPPU (forchlorfenuron) concentrations (0, 5, 10 mgL⁻¹) to grape fruitlets.
• Gas-chromatography mass-spectrometry (GC-MS) analysis to quantify volatile compounds.
• RNA sequencing (RNA-Seq) coupled with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis to identify DEGs and their functions.
• Quantitative real-time PCR (qRT-PCR) to validate RNA-seq findings.

Main Results:

• CPPU (forchlorfenuron) treatment significantly altered volatile profiles, decreasing terpenoids and aromatics (e.g., linalool, geraniol) while increasing aliphatics (e.g., hexanol).
• RNA-Seq identified numerous DEGs, with pathway enrichment analysis highlighting involvement in fatty acid metabolism, phenylpropanoid and carotenoid biosynthesis, and plant hormone signal transduction.
• Key genes including CCDs, LOX, GGDP reductase, and PAL were found to be closely associated with volatile compound formation in CPPU-treated berries.

Conclusions:

• CPPU (forchlorfenuron) treatment significantly impacts grape berry volatile biosynthesis pathways at the transcriptomic level.
• This study provides the first sequential transcriptomic atlas of CPPU-affected grape berries, enhancing understanding of volatile compound regulation.
• The findings offer valuable insights for optimizing viticulture practices and developing new grape varieties with desired flavor profiles.