Nam, Hong Gil, Ph.D.

Professor
Department of Life Science
Division of Molecular and Life Sciences
Plant Molecular Biology and Genetics

Publications Abstract
E-mail nam@postech.ac.kr
Phone +82-54-279-2111(office)
          +82-54-279-2972(lab.)
Laboratory Nam Laboratory for Complex Biology

Profile |  Research Interests  |  Selected Publications

Profile

Research Interests

Plant Molecular Genetics
Advances in plant molecular genetics and genomics provide a new opportunity to elucidate new knowledge in plant sciences. Utilizing and developing these approaches, this laboratory, now assigned as a national research lab, is involved in the following topics. In addition, we are also conducting some biotechnological application of these studies, including development of transgenic crop plants with stress-tolerance, flowering timing, and delayed senescence, etc. In these topics, we are utilizing the in planta transformation procedures established for a few crop plants. 

1. Plant functional genomics.
Random antisense mutagenesis. Most of cellular processes in an organism depend on functions of expressed sequences. Thus, an efficient large-scale functional assignment of expressed sequences is crucial for ultimate understanding of cellular processes. Toward this goal in plants, we designed random antisense mutagenesis (RAM) approach. In this approach, a library of transgenic plants that express random cDNA molecules in the antisense orientation is generated by in planta transformation with an Agrobacterium culture harboring a plant antisense cDNA library. Cellular functions of random cDNA clones are identified by screening mutant phenotypes in the transgenic plant pool. A cDNA clone responsible for a mutation, then, can be isolated by a simple cloning procedure involving polymerase chain reaction (PCR). We already isolated a few genes that control plant development by this approach. Through this approach, it should be possible to assign a large number of expressed sequences with known in vivo functions in plants.
We are also applying activation

2. Molecular Genetic analysis of plant senescence   
Senescence, although a deteriorative cellular process in its nature, is assumed to be an evolutionarily acquired, active genetic trait that makes an important contribution to fitness of plants, for example by remobilizing nutrient from vegetative tissues to reproductive organs. Elucidating the genetic mechanism of leaf senescence should be essential for the understanding of the senescence phenomenon itself and also for practical purposes such as the improvement of plant productivity, pre- or post-harvest storage, stress tolerance, etc. However, in spite of the biological and practical importance of leaf senescence, the genetic mechanism controlling the leaf senescence process remains poorly understood. We are conduction genetic and molecular analysis of plant senescence utilizing Arabidopsis. We have identified 5 delayed senescence mutants and cloned two genes by map-based cloning. We are also identifying senescence-regulating genes by assaying the functions of senescence-induced clones.

3. Light-mediated control of plant development.
Light plays a pivotal role in plant growth and development not only as an energy source for photosynthesis but also as a environmental stimuli for many developmental processes. We are taking genetic and molecular approaches to dissect the phytochrome-mediated developmental control. Our focus is identification of phyA-mediated signal transduction components and of interaction between light and auxin in plant morphorgenesis. Photoperiodic responses in plants include day-length dependent flowering. We are studying the mechanism of photoperiodic flowering responsses, focuing on the role of the GI gene in Arabidopsis. Mutations in the Arabidopsis thaliana GIGANTEA (GI) gene cause photoperiod-insensitive flowering and alteration of circadian rhythms. The GI gene encodes a protein containing 6 putative transmembrane domains. Circadian expression patterns of the GI gene and the clock-associated genes, LHY and CCA1, are altered in gi mutants, showing that GI is required for maintaining circadian amplitude and appropriate period length of these genes. The gi-1 mutation also affects light signaling to the clock, suggesting that GI participates in a feedback loop of the plant circadian system.

Selected Publications 

1. Jin Hee Kim, Hye Ryun Woo, Jeongsik Kim, Pyung Ok Lim, In Chul Lee, Seung Hee Choi, Daehee Hwang and Hong Gil Nam (2009) Trifurcate feed-forward regulation of age-dependent cell death involving miR164 in Arabidopsis. Science 323, 1053-1057
2. Hyo Jung Kim, Sung Aeong Oh, Lynette Brownfield, Sung Hyun Hong, Hojin Ryu, Ildoo Hwang, David Twell, Hong Gil Nam (2008) Control of plant male germ cell proliferation by SCF^FBL17 mediated degradation of cell cycle inhibitors. Nature 455, 1134-1137.
3. Pyung Ok Lim, Hyo Jung Kim, Hong Gil Nam (2007) Leaf Senescence. Annual Review of Plant Biology 58. 115-136.
4. Hyo Jung Kim, Hojin Ryu, Sung Hyun Hong, Hye Ryun Woo, Pyung Ok Lim, In Chul Lee, Jen Sheen, Hong Gil Nam and Ildoo Hwang (2006) Cytokinin-mediated control of leaf longevity by AHK3 through phosphorylation of ARR2 in Arabidopsis. Proc. Natl. Acad. Sci. USA, 103, 814-819
5. Jong Sang Ryu, Jeong-Il Kim, Tim Kunkel, Byung Chul Kim, Dae Shik Cho, Sung Hyun Hong, Seong-Hee Kim, Aurora Piйas Fernandez, Yumi Kim, Jose M. Alonso, Joseph R. Ecker, Ferenc Nagy, Pyung Ok Lim, Pill-Soon Song, Eberhard Schefer, and Hong Gil Nam (2005) Phytochrome-specific type 5 phosphatase controls light signal flux by enhancing phytochrome stability and affinity for a signal transducer. Cell 120, 395-406.

Division of Molecular & Life Sciences| POSTECH