Zhi-Yan (Rock) Du

  • Feb 6, 2018

Date & Location: February 6, 2018, at 12p; Room 168 Plant Biology Building

Subject: Chlamydomonas Galactoglycerolipid Lipase PGD1 is involved in thylakoid membrane remodeling in response to adverse environmental conditions

Abstract: Photosynthesis occurs in the thylakoid membrane where the predominant lipid is monogalactosyldiacylglycerol (MGDG). As environmental conditions change, photosynthetic membranes have to adjust. Here we used a loss-of-function mutant deficient in the MGDG-specific lipase PGD1 (PLASTID GALACTOGLYCEROLIPID DEGRADATION1) to investigate the link between MGDG turnover, ultrastructure of chloroplasts and the production of reactive oxygen species (ROS) in response to different adverse environmental conditions. The pgd1 mutant showed altered MGDG abundance and acyl composition and altered abundance of photosynthesis complexes with an increased PSII/PSI ratio. Subsequent transmission electron microscopy showed hyperstacking of the thylakoid grana in the pgd1 mutant, which also exhibited increased ROS production during N deprivation and high light exposure.

Supplementation of the medium with bicarbonate or treatment with DCMU protected the cells against oxidative stress in the light and reverted chlorosis of pgd1 cells during N deprivation. Furthermore, exposure to stress conditions such as cold and high osmolarity induced the expression of PGD1, and loss of PGD1 in the mutant led to increased ROS production and inhibited cell growth. These findings suggest essential roles for PGD1 in maintaining appropriate thylakoid membrane composition and structure, affecting growth and stress tolerance when cells are challenged during adverse conditions.

Rock is a post-doc in the lab of Christoph Benning.