The Role of GIGANTEA in mediating metabolic input in to the Arabidopsis circadian clock

点击翻译按钮获取中文摘要

Most living organisms measure time. We are familiar with our human 'body clock' which acts as an internal watch allowing us to sleep and wake up at regular time intervals. In particular, we experience the physiological effects of disruption of the clock when we cross time zones and get jet-lag. Plants also measure time and use this information to measure the length of the seasons and to control flowering. Many plant behaviours only occur at specific times of the day, for example water lily flowers are only open in the middle of the day and close long before dusk. We have recently found that plants with a functional clock grow faster than plants that do not have a working clock. The time-keeper in plants is present in every cell and is known as a circadian clock. We have new data that demonstrate that sugar can regulate the behaviour of the circadian clock. This is important because in plants, there are rhythmic changes in the content of sugar in the cells. In the day, using the energy from sunlight, plants make sugar by photosynthesis. At night the sugar content of cells is low because there is no photosynthesis. Our finding that sugar regulates the behaviour of the circadian clock suggests a mechanism by which the metabolism of plants regulates daily rhythms of other activities. We have identified one of the genes required for the sensing of sugar by the plant circadian clock. This is GIGANTEA (GI), a gene already known to be part of the clock. We now want to understand how GI responds to sugar and how this affects the function of the clock. We will measure how sugar affects the GI gene and interactions between the GI protein with other proteins. Sugar does not only regulate the circadian clock. Sugar affects the development of the plant and regulates many genes. We will find out if GI has a role in sugar-mediated changes in development and gene activity, in addition to its role in sugar regulation of the clock. This will find out if GI is part of a general sugar sensing mechanism. We hope to find other genes important for sugar sensing by the circadian clock. We will look for effects of other genes of the circadian clock on sugar sensing. We also will investigate whether other genes already known to have a role in other sugar-sensing pathways also have an effect on sugar sensing by the clock. A major goal of our project is to find out why sugar affects the plant circadian clock. We will do this by studying the growth and physiology of plants with genetically-manipulated levels of the GI gene in environments that affect the sugar content of the plant. This understanding of the physiological role of GI and sugar sensing is an essential step in planning how to produce crop plants that grow faster, are healthier, larger or produce new products, such as biofuels.