Hwang, Il-Doo, Ph.D.

Associate Professor
Department of Life Science
Division of Molecular and Life Sciences
Plant Biochemistry

Publications Abstract
E-mail  ihwang@postech.ac.kr
Phone  054-279-2291
Laboratory  Development Signaling Network Lab.

Profile |  Research Interests  |  Selected Publications

Profile

Research Interests

Our main interests are to elucidate intracellular signal transduction pathways controlling plant growth and development, and to develop new tools for agricultural and environmental improvement. We are currently focused on the elucidation of cytokinin signal transduction mechanism in plants.

Cytokinins are essential plant hormones that are involved in the regulation of cell division, and diverse processes of plant growth and development. These processes include senescence, apical dominance, shoot meristem initiation, leaf and root differentiation, and chloroplast biogenesis. Cytokinins can reprogram terminally differentiated cells into stem cells and promote subsequent shoot regeneration indefinitely in cultured cells in combination with another phytohormone, auxin. Recent genetic and molecular studies in various plant species have suggested the involvement of two-component signaling proteins in cytokinin signal transduction.

Two-component systems - consisting of a histidine protein kinase that senses the input and a response regulator that mediates the output - control signal transduction pathways in many prokaryotes and in some eukaryotes (Fig. A, B). The signaling pathway is initiated when a histidine protein kinase sensor, modulated by an environmental cue, phosphorylates its own conserved histidine residue and transfers the phosphate to a conserved aspartate residue of a response regulator. In some cases, additional phosphotransfer steps may intervene between the histidine protein kinase and response regulator, mediated by a histidine phosphotransmitter.

The completion of the Arabidopsis genome sequence has revealed 54 genes encoding putative AHK, AHP and ARR proteins, suggesting an important involvement of the ancient and conserved signaling mechanism in many facets of plant cell regulation.

The development of the Arabidopsis protoplast system has enabled a functional genomic analysis of the two-component regulators, and deciphered a cytokinin signaling pathway in Arabidopsis. The pathway integrates multiple histidine protein kinase activities to common AHP proteins, which serve as cytoplasm/nuclear shuttles, and to distinct ARR proteins in the nucleus.

We use a combinational approach with genetic, genomic, and biochemical tools to elucidate the details in cytokinin perception, protein-protein interactions, and target gene expressions essential in cytokinin signaling. We will further determine how cytokinin, with a conserved short signaling circuitry, control cell division, and diverse processes of plant growth at different development stages.

Selected Publications 

1. Jaemyung Choi, Daeseok Choi, Seungchul Lee, Choong-Min Ryu, Ildoo Hwang, 2011, Cytokinins and plant immunity: old foes or new friends? , Trends in Plant Science
2. Jaemyung Choi, Sung Un Huh, Mikiko Kojima, Hitoshi Sakakibara, Kyung-Hee Paek, Ildoo Hwang, 2010, The Cytokinin-Activated Transcription Factor ARR2 Promotes Plant Immunity via TGA3/NPR1-Dependent Salicylic Acid Signaling in Arabidopsis, Developmental Cell, 19: 284-295,
3. Hojin Ryu*, Kangmin Kim*, Hyunwoo Cho, Ildoo Hwang, 2010, Predominant actions of cytosolic BSU1 and nuclear BIN2 regulate subcellular localization of BES1 in brassinosteroid signaling. Mol. Cells 29:291-296.
4. Hojin Ryu, Hyunwoo Cho, Kangmin Kim, lldoo Hwang, 2010, Phosphorylation dependent nucleocytoplasmic shuttling of BES1 is a key regulatory event in brassinosteroid signaling. Mol. Cells 29:283-290.
5. Hejatko J*, Ryu HJ*, Kim GT, Dobesova R, Choi S, Choi SM, Soucek P, Horak J, Pekarova B, Palme K, Brzobohaty B, Hwang I, 2009, The Histidine Kinases CYTOKININ-INDEPENDENT1 and ARABIDOPSIS HISTIDINE KINASE2 and 3 Regulate Vascular Tissue Development in Arabidopsis Shoots. Plant Cell 21:2008-2021.
6. Ryu HJ, Kim KM, Hwang I, 2008, Spatial redistribution of key transcriptional regulators in brassinosteroid signaling. Plant signaling & behavior 3:1-3.
7. Ryu HJ*, Kim KM*, Cho HW, Park JH, Choe SH, and Hwang I, 2007, Nucleocytoplasmic shuttling of BZR1 mediated by phosphorylation is essential in Arabidopsis brassinosteroid signaling. Plant Cell 19:2749-2762.
8. Choi J and Hwang I, 2007, Cytokinin: Perception, signal transduction, and role in plant growth and development.Journal of Plant Biology 50:98-108.
9. Kim HJ, Ryu H, Hong SH, Woo HR, Lim PO, Lee IC, Sheen J, Nam HG, Hwang I, 2006, Cytokinin-mediated control of leaf longevity by AHK3 through phosphorylation of ARR2 in Arabidopsis. PNAS 103:814-819.
10. Hwang I, Sakakibara H, 2006, Cytokinin biosynthesis and perception. Physiologia Plantarum 126:528-538

Division of Molecular & Life Sciences| POSTECH