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Special (비정기세미나)
2004.04.08 00:41

제7회 정기세미나

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1. 연사 : 김정묵 박사 - 전남대 APSRC (Agricultural Plant Stress Research Center)
2. 연제 : Signaling Networks in Plants
3. 일시 : 2004년 4월 13일 (화) 오후 4:00
4. 장소 : 의과학센터 원격강의실

※ 문의 : 최길주 교수님 (2636)

※ Abstract
Low temperature induces expression of a number of genes that encode proteins enhancing tolerance to freezing temperatures in plants. A cis-acting element responsive to cold and drought, the C-repeat/dehydration-responsive element (C/DRE), was identified in the Arabidopsis stress-inducible genes RD29A and COR15a, and found in other cold-inducible genes in various plants. Although C/DRE-binding factor/DRE-binding protein (CBF/DREB) has been established as a critical component during the cold-acclimation response, signaling pathways and networks are mostly unknown. To circumvent the problems associated with the complicated interactive effects of various cis-acting elements in the whole promoter region in studying signaling pathways and networks, we generated transgenic Arabidopsis containing multiple copies of the synthetic C/DRE fused to a GUS reporter gene with a minimal promoter (MP) containing TATA box (4C/DRE-GUS), that responds to cold. We show that light signaling mediated by phytochrome B photoreceptor was shown necessary for cold-induced gene expression through the C/DRE. We employed targeted-genetic approach to isolate Arabidopsis mutants exhibiting altered cold-responsive gene expression (acg), and identify ACG1 as a negative regulator of the CBF/DREB pathway. acg1 showed the late-flowering phenotype with the elevated level of FLOWERING LOCUS C (FLC), a repressor of flowering encoding a MADS-box protein. We showed that acg1 is a null allele of the autonomous pathway gene FVE. FVE encodes a homolog of the mammalian retinoblastoma-associated protein, a component of a histone deacetylase (HDAC) complex involved in transcriptional repression. We also showed that plant senses intermittent cold-stress via FVE and delays the flowering with increasing FLC expression. These results suggest that dual roles of FVE in regulating the flowering-time as well as the stress-response to cold may have an evolutionary advantage for plants increasing their survival rates.
In another approach, we used differential display of mRNA to isolate the genes induced early in response to low temperature, based on reasoning that some of the components playing important roles in signaling will be expressed fast and primarily upon environmental stimuli. We focus on three interesting genes encoding putative signaling components. I will present some of the results that we have obtained with reverse genetic methods to characterize potential roles of these components in plant signaling.
In the end of my talk, I will briefly present some of our results on roles of Aux/IAA genes in plant hormone auxin response.



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