School of Interdisciplinary Bioscience and Bioengineering and Department of Computer Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea and Department of New Biology and Center for Plant Aging Research, Institute for Basic Science, Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873, Korea School of Interdisciplinary Bioscience and Bioengineering and Department of Computer Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea and Department of New Biology and Center for Plant Aging Research, Institute for Basic Science, Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873, Korea.