Jin, Jing Bo , Jin, Yin Hua , Lee, Jiyoung , Miura, Kenji , Yoo, Chan Yul , Kim, Woe-Yeon , Hyun, Youbong , Somers, David. E , Lee, Ilha , Yun, Dae-Jin , Bressan, Ray A. , Hasegawa, Paul M. .
Arabidopsis SUMO-E3 ligase, AtSIZ1 modulates FLD activity through SUMO modification.
This study establishes that loss-of-function siz1 mutations (siz1-2 and siz1-3) cause substantial early flowering under short days, which is suppressed by expressing SIZ1. siz1 mutations down-regulate expression of FLOWERING LOCUS C (FLC) compared to wild type and partially suppress late flowering of FRI-Col plant. These results indicate that SIZ1 represses transition to flowering and promotes expression of FLC. Genetic and molecular analyses of double mutants show that the early flowering phenotype and down-regulated FLC transcript level caused by siz1 mutation are suppressed by mutations to autonomous floral promotion pathway gene, FLOWERING LOCUS D (FLD), indicating that SIZ1 functions upstream of FLD within the autonomous pathway. FLD is sumoylated in wild type but to a less extent in siz1-2. FLD has three predicted sumoylation motifs and mutations to lysine residues in these (FLDK3R) abolish SUMO modification of the protein. These results indicate that SIZ1 facilitates SUMO conjugation to sumoylation motif(s) of FLD. Expression of FLDK3R (sumoylation defective) reduces acetylation status of histone H4 in FLC chromatin relative to the expression of native FLD. These results indicate that SIZ1-mediated SUMO modification of FLD represses its activity to facilitate deacetylation of histones in FLC chromatin, and implicate sumoylation as a post-translational control process of the autonomous floral promotion pathway. The siz1 plant accumulates higher level of salicylic acid (SA) and expression of nahG protein in siz1 (SA deficient plant) strongly suppressed early flowering phenotype of siz1. This result suggests that SIZ1 may negatively regulate SA dependent stress induced flowering under non-stress conditions.
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1 - Purdue University, Center for Plant Environmental Stress Physiology, 625 Agriculture Mall Dr, West Lafayette, IN, 47907, USA
2 - Purdue University, Center for Plant Environmental Stress Physiology
3 - Ohio State University, Department of Plant Cellular and Molecular Biology
4 - Seoul National University, Department of Biological Sciences
5 - Gyeongsang National University, Division of Applied Life Science (BK21 program), and Environmental Biotechnology National Core Research Center
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM