what has gene cloning revealed?
Takamiya KI; Tsuchiya T; Ohta H Dept of Biological Sciences, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8501, Japan. The mechanism responsible for the degreening of plants and the degradation of chlorophyll was unclear for many years. However, recent studies have identified the colorless intermediates and helped to construct a basic pathway for degradation. After the successive removal of phytol and Mg21 from the chlorophyll molecule by chlorophyllase and ‘Mg dechelatase’, pheophorbide a is cleaved and reduced to yield a colorless, open tetrapyrrole intermediate. After further modifications, this is finally transported to the vacuole. Cloning the genes for chlorophyllase isozymes and the reductase should help to elucidate the physiological roles of each enzyme at a molecular level.
