Abstract：

This study presents a groundbreaking approach to enhancing the economic value of cotton by genetically engineering the synthesis of astaxanthin, a high-value lipid-soluble carotenoid with potent antioxidant properties. Through synthetic biology and metabolic engineering, researchers introduced two algal-derived genes (CrBKTandHpBHY) into cotton (Gossypium hirsutumcv. Zhongmian49) under the control of a constitutive promoter (CmpL), enabling efficient astaxanthin production.

Tissue-Specific Accumulation: Transgenic cotton lines (TY) exhibited orange-red pigmentation in leaves, boll shells, and cotyledons, with leaves accumulating up to 61.03 mg/kg astaxanthin (fresh weight)—comparable to astaxanthin-rich maize seeds.

By-Product Valorization: Astaxanthin-enriched leaves and boll shells offer novel opportunities as livestock feed additives, while astaxanthin-colored cottonseed oil (410 μg/kg) enhances market value.

Fiber Limitations: Despite co-expressing additional genes (PaCrtI and ZmPSY1) to boost precursor supply, astaxanthin synthesis in fibers remained undetectable, likely due to insufficient metabolic flux.

Future Directions: The study highlights the need to re-engineer terpene pathways in fibers for sustainable colored cotton production, positioning this work as a foundation for advancing green biotechnology in agriculture.

Key Words: Astaxanthin, cotton, livestock feed