Enhanced polyhydroxybutyrate production in transgenic sugarcane.

Area of Science:

• Biotechnology
• Plant Molecular Biology
• Biomaterials Science

Background:

• Polyhydroxybutyrate (PHB) is a biodegradable polyester with properties similar to conventional plastics.
• Plant-based production of PHB offers a sustainable alternative to petrochemical plastics.
• Previous studies achieved 1.8% PHB in transgenic sugarcane leaves without impacting biomass.

Purpose of the Study:

• To enhance PHB production in transgenic sugarcane.
• To evaluate the efficacy of different plant and viral promoters for increasing PHB levels.
• To identify optimal promoter strategies for high-yield PHB accumulation in sugarcane.

Main Methods:

• Transgenic sugarcane lines were generated using various constructs (single-gene and multigene).
• Different promoters were tested, including maize and rice polyubiquitin (Ubi) promoters, maize chlorophyll A/B-binding protein promoter, and a Cavendish banana streak badnavirus promoter.
• PHB levels were quantified using leaf dry weight measurements.

Main Results:

• The Cavendish banana streak badnavirus promoter initially yielded high PHB but showed silencing in mature plants.
• Rice and maize Ubi promoters resulted in comparable PHB production levels.
• The maize chlorophyll A/B-binding protein promoter achieved 4.8% PHB in leaf dry weight, a ~2.5-fold increase over previous records.
• High-PHB lines exhibited reduced biomass and slight chlorosis compared to wild-type sugarcane.

Conclusions:

• The maize chlorophyll A/B-binding protein promoter is effective for significantly boosting PHB production in sugarcane.
• While high yields were achieved, associated phenotypic changes require further investigation for commercial viability.
• Optimized promoter selection is crucial for advancing sugarcane as a platform for biorenewable plastic production.