Biological Clock Controls Carbohydrate Metabolism in Arabidopsis at night

Plants are fueled through phosynthesis during daytime, while at nighttime, the plants break down starch for growth. In previous studies, Arabidopsis was observed to have linear rate of starch degradation at night and starch is almost completely consumed by dawn. Alexander Graf from the Department of Metabolic Biology in the United Kingdom, together with other scientists, conducted experiments to test the hypothesis that starch degradation at night is under circadian control, and investigate the consequences for growth. When Arabidopsis was exposed to dark earlier than usual, normal degradation of starch took place. However, when the plant was exposed to abnormal day lengths (28 hours or 17 hours), the starch was exhausted even before the actual time of dawn.

A mutant without LHY and CCA1 clock components used up its starch at dawn by its initial circadian clock, instead of the actual dawn time. Reduced growth was observed in wild plants exposed to 28-hour day length and the mutants exposed to 24-hour day length. This reduction of growth is attributed to the inappropriate starch degradation and the subsequent carbon shortage at the end of the night. Therefore, starch usage is controlled by the 24-hour circadian rhythym to ensure that there is efficient carbohydrate degradation until next anticipated dawn, and this is important for maintaining plant productivity.

The research paper is available at http://www.pnas.org/content/107/20/9458.full.