Biochemical insights on degradation of Arabidopsis DELLA proteins gained from a cell-free assay system.
The phytohormone gibberellic acid (GA) regulates diverse aspects of plant growth and development. GA responses are triggered by the degradation of DELLA proteins, which function as repressors in GA signaling pathways. Recent studies in Arabidopsis thaliana and rice (Oryza sativa) have implied that the degradation of DELLA proteins occurred via the ubiquitin-proteasome system. Here, we developed an Arabidopsis cell-free system to recapitulate DELLA protein degradation in vitro. Using this cell-free system, we documented that Lys-29 of ubiquitin is the major site for ubiquitin chain formation to mediate DELLA protein degradation. We also confirmed the specific roles of GA receptors and multisubunit E3 ligase components in regulating DELLA protein degradation. In addition, blocking DELLA degradation with a PP1/PP2A phosphatase inhibitor in our cell-free assay suggested that degradation of DELLA proteins required protein Ser/Thr dephosphorylation activity. Furthermore, our data revealed that the LZ domain of Arabidopsis DELLA proteins is essential for both their stability and activity. Thus, our in vitro degradation system provides biochemical insights into the regulation of DELLA protein degradation. This in vitro assay system could be widely adapted for dissecting cellular signaling pathways in which regulated proteolysis is a key recurrent theme.
Wang
Feng
F
National Institute of Biological Sciences, Zhongguancun Life Science Park, Beijing 102206, China.
Zhu
Danmeng
D
Huang
Xi
X
Li
Shuang
S
Gong
Yinan
Y
Yao
Qinfang
Q
Fu
Xiangdong
X
Fan
Liu-Min
LM
Deng
Xing Wang
XW
D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002474:Cell-Free System / Q000378:metabolism*; D044842:Cullin Proteins / Q000235:genetics / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005875:Gibberellins / Q000378:metabolism; D047468:Immunoprecipitation; D010766:Phosphorylation / Q000187:drug effects; D017354:Point Mutation; D055550:Protein Stability; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; C100318:Cullin 1; D044842:Cullin Proteins; D004791:Enzyme Inhibitors; D005875:Gibberellins; D025801:Ubiquitin; C007842:gibberellic acid