Plant lipid's response to frigid temperature revealed (1/21/2008)

Chinese scientists are learning how plants survive extremely cold temperatures by testing Arabidopsis thaliana

Low-temperature stress is a chief environment factor that hinders plant growth, development as well as its geographic distribution and yield. Cell membrane is the major part of a plant where the harm takes place and the molecular changes in the membrane and membrane lipid are one of the initial signals in plant adaptation to and survival after freezing.

Plant response to cold and freezing involves three distinct phases: cold acclimation, freezing, and post-freezing recovery. Considerable progress has been made toward understanding lipid changes during cold acclimation and freezing, but little is known about lipid alteration during post-freezing recovery.

In collaboration with its co-workers at home and abroad, a research team headed by Prof. LI Weiqi with CAS Kunming Institute of Botany has made progress in revealing mechanisms behind the changes in the plant lipid's response to frigid temperature when the plant's tissue freezes or thaws. The research paper has been published by the monographic Journal of Biological Chemistry, 283:461-468.

Under the title of "Differential degradation of extraplastidic and plastidic lipids during freezing and post-freezing recovery in Arabidosis thaliana," the researchers give a comparative analysis of the changing details in the molecular structure taking place in 120 membrane lipids sampled from the plant Arabidosis thaliana in the wild and its mutated strains during their tissue's freezing and thawing processes.

They took advantage of the well-established methods of lipidomics to make a detailed and systematic analysis of the changes in the three stages occurring in the molecular structure of A. thaliana's membrane lipid. The research work shows that large-scale changes in the lipid's profile come into being during the two stages of freezing and post-freezing recovery. But, the molecular alternations in different kinds of the lipid vary. In a freezing process, the lipid hydrolysis occurs mostly in phospholipids outside the cell's major organelles known as plastids, i.e. extraplastidic phospholipids while in the post-freezing recovery, the hydrolysis of lipids takes place mostly in plastidic lipids. When the degradation of extraplastidic lipids ceases, the degradation of plastidic lipids increases.

The research also indicates the activation of lipid-degradng enzymes is triggered at specific sites in the cell in the different phases of the freezing and thawing processes. In addition, the researchers further investigated the role played by two kinds of phospholipase PLD?1 and PLD?. They found the former can help the hydrolysis of plastic lipids in freezing and post-freezing recovery and phospholipid hydrolysis in post-freezing recovery is also increased in PLD?-deficient plants. These findings suggest a negative role shown by PLD?l and a positive role displayed by PLD? in freezing tolerance.

Note: This story has been adapted from a news release issued by the Chinese Academy of Sciences

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