Diversion of Carbon Flux from Sugars to Lipids Improves the Growth of an Arabidopsis Starchless Mutant

The Science

Researchers hoped to test if redirecting carbon from seed carbohydrate to vegetative lipids relieves growth inhibition. To test the role of lipids in plant growth, transgenic plants overexpressing PDAT1 in adg1 mutants were generated and grown under a 16-h/8-h day/night cycle.

The Impact

• Overexpression of PDAT1 enhances fatty acid and triacylglycerol (TAG) synthesis at the expense of soluble sugars.
• Lipids in the form of TAG can partially replace the function of starch in maintaining energy homeostasis and plant growth in starchless mutants.
• This study improved understanding of how increasing TAG accumulation affects plant growth.

Summary

Inactivation of ADP-glucose pyrophosphorylase1 (ADG1) causes a starchless phenotype in Arabidopsis. Mutants defective in ADG1 show severe growth retardation in day/night conditions but exhibit similar growth to wild type under continuous light, implying that starch plays an important role in supporting respiration, metabolism and growth at night. In addition to carbohydrates, lipids and proteins can serve as alternative respiratory substrates for the energy production in mature plants. Researchers demonstrated that unlike sugars, which were metabolized within a few hours of darkness, TAG breakdown was slow, occurring throughout the entire dark period. The slow pace of TAG hydrolysis provided a sustained supply of fatty acids for energy production, thereby alleviating energy deficiency at night and thereby improving the growth of the starchless mutants. Lastly, researchers conclude that lipids can contribute to plant growth by providing a constant supply of fatty acids as an alternative energy source in mature starchless mutant plants.

Funding

This effort jointly supported by BES Physical Biosciences.

References

Fan, J., C. Zhao, L. Yu, P. Li, J. Shanklin, C. Xu. 2019. “Diversion of Carbon Flux from Sugars to Lipids Improves the Growth of an Arabidopsis Starchless Mutant,” Plants 8(7), 229. DOI:10.3390/plants8070229.