A transcriptomic view to wounding response in young Scots pine stems.

Area of Science:

• Plant Biology
• Forestry Science
• Molecular Biology

Background:

• Scots pine (Pinus sylvestris) xylem plays a crucial role in tree structure and defense.
• Mechanical wounding triggers complex physiological and molecular responses in plants.
• Understanding xylem's reaction to injury is vital for forest health and wood quality.

Purpose of the Study:

• To investigate the temporal gene expression patterns in Scots pine xylem following mechanical wounding.
• To identify key molecular pathways involved in the wound response.
• To compare wound-induced responses with those during natural developmental processes like heartwood formation.

Main Methods:

• RNA sequencing was employed to analyze gene expression in five-year-old Scots pine xylem at multiple time points post-wounding (3 hours, 1 day, 4 days).
• Quantitative analysis of transcriptomic data identified differentially expressed genes and pathways.
• Comparative analysis with existing data on heartwood formation was performed.

Main Results:

• A bimodal gene expression pattern was observed in response to wounding.
• Early response (3 hours) included induction of water deficit, defense, and cell wall modification genes, with down-regulation of growth processes.
• Later response (1-4 days) involved activation of secondary metabolism, including stilbene and lignan biosynthesis; pine resin biosynthesis was not induced within four days.
• Wounding-induced processes showed overlap with heartwood formation, particularly in defense and desiccation stress pathways, but with distinct transcript regulation.

Conclusions:

• Scots pine xylem mounts a dynamic, multi-phase defense strategy against mechanical injury.
• Stilbene biosynthesis is a key component of the wound response, serving as a defense mechanism.
• The study highlights both conserved and unique molecular mechanisms underlying wound response and heartwood formation in Scots pine.