The RrHY5-RrNAC2-RrOSC5 Module Promotes UV-B-Induced Sterol Defence in Rosa roxburghii

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Rosa roxburghii Tratt. exhibits high ultraviolet-B (UV-B) tolerance, with plant sterols crucial for adaptation.
• The precise regulatory mechanisms governing sterol-mediated UV-B tolerance in this species are largely unknown.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying UV-B-induced sterol biosynthesis and tolerance in Rosa roxburghii Tratt.
• To identify key genes and transcription factors involved in this adaptive pathway.

Main Methods:

• Gene cloning and characterization of RrOSC5, an oxidosqualene cyclase.
• Analysis of RrOSC5 expression under UV-B stress.
• Promoter analysis and transcription factor binding assays for RrNAC2.
• Heterologous expression of RrNAC2 in tobacco.
• Protein-protein interaction studies between RrHY5 and RrNAC2.

Main Results:

• RrOSC5, encoding cycloartenol synthase, is upregulated by UV-B stress and enhances sterol accumulation and UV-B resistance.
• Transcription factor RrNAC2 directly activates RrOSC5 transcription and confers UV-B tolerance upon heterologous expression.
• RrHY5 interacts with RrNAC2, integrating the RrNAC2-RrOSC5 module into the UV-B signaling pathway.
• A hierarchical RrHY5-RrNAC2-RrOSC5 cascade regulates UV-B-induced sterol defense, enhancing antioxidant and osmotic adjustment.

Conclusions:

• A novel signaling cascade involving RrHY5, RrNAC2, and RrOSC5 governs UV-B-induced sterol biosynthesis and tolerance in Rosa roxburghii Tratt.
• This pathway enhances plant defense mechanisms against UV-B stress.
• Findings offer insights for molecular breeding of fruit plants with improved UV-B resistance.