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

RrOSC5, encoding a functional cycloartenol synthase, is dynamically upregulated by UV-B in Rosa roxburghii and overexpression increases sterol accumulation and UV-B resistance.

• Why it matters: Plant sterols are critical for Rosa roxburghii UV-B adaptation, but the regulatory pathway controlling sterol biosynthesis under UV-B stress was unknown.
• What they did: The study identified RrOSC5 and showed RrNAC2 directly binds a non-canonical AC-rich repeat in the RrOSC5 promoter to activate transcription; RrHY5 physically interacts with RrNAC2.
• The result: Heterologous overexpression of RrNAC2 in tobacco conferred enhanced UV-B tolerance, supporting a hierarchical RrHY5–RrNAC2–RrOSC5 cascade for UV-B-induced sterol defence and related antioxidant/osmotic adjustments.

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