BPM-CUL3 E3 ligase modulates thermotolerance by facilitating negative regulatory domain-mediated degradation of DREB2A in Arabidopsis
Thursday, 2017/10/05 | 08:17:04
|
Kyoko Morimoto, Naohiko Ohama, Satoshi Kidokoro, Junya Mizoi, Fuminori Takahashi, Daisuke Todaka, Junro Mogami, Hikaru Sato, Feng Qin, June-Sik Kim, Yoichiro Fukao, Masayuki Fujiwara, Kazuo Shinozaki, and Kazuko Yamaguchi-Shinozaki PNAS October 3 2017; vol.114; no.40: E8528–E8536 SignificanceDEHYDRATION-RESPONSIVE ELEMENT-BINDING PROTEIN 2A (DREB2A) is a key transcription factor for plant adaptation to drought and heat. DREB2A activity is strictly regulated via proteolysis mediated by the negative regulatory domain (NRD), although the molecular basis for this regulation has remained unclear for a decade. We reveal that BTB/POZ AND MATH DOMAIN proteins (BPMs), substrate adaptors for Cullin3-based E3 ubiquitin ligase, are the long-sought factors responsible for NRD-dependent DREB2A degradation. Through DREB2A degradation, BPMs negatively regulate the heat stress response and prevent the adverse effects of excess DREB2A on plant growth. Furthermore, we found the BPM recognition motif in various transcription factors, implying a general contribution of BPM-mediated proteolysis to divergent cellular responses via an accelerated turnover of transcription factors. AbstractDEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN 2A (DREB2A) acts as a key transcription factor in both drought and heat stress tolerance in Arabidopsis and induces the expression of many drought- and heat stress-inducible genes. Although DREB2A expression itself is induced by stress, the posttranslational regulation of DREB2A, including protein stabilization, is required for its transcriptional activity. The deletion of a 30-aa central region of DREB2A known as the negative regulatory domain (NRD) transforms DREB2A into a stable and constitutively active form referred to as DREB2A CA. However, the molecular basis of this stabilization and activation has remained unknown for a decade. Here we identified BTB/POZ AND MATH DOMAIN proteins (BPMs), substrate adaptors of the Cullin3 (CUL3)-based E3 ligase, as DREB2A-interacting proteins. We observed that DREB2A and BPMs interact in the nuclei, and that the NRD of DREB2A is sufficient for its interaction with BPMs. BPM-knockdown plants exhibited increased DREB2A accumulation and induction of DREB2A target genes under heat and drought stress conditions. Genetic analysis indicated that the depletion of BPM expression conferred enhanced thermotolerance via DREB2A stabilization. Thus, the BPM-CUL3 E3 ligase is likely the long-sought factor responsible for NRD-dependent DREB2A degradation. Through the negative regulation of DREB2A stability, BPMs modulate the heat stress response and prevent an adverse effect of excess DREB2A on plant growth. Furthermore, we found the BPM recognition motif in various transcription factors, implying a general contribution of BPM-mediated proteolysis to divergent cellular responses via an accelerated turnover of transcription factors.
See: http://www.pnas.org/content/114/40/E8528.abstract.html?etoc
Figure 1: BPM2 is a DREB2A-interacting protein. (A) Validation of interactions between DREB2A and the candidate interactors by Y2H assay. The growth of yeast strains on nonselective medium (−LW) and selective medium (−LWHA) is shown. (B) Subcellular localization of DREB2A, BPM2, and BPM4 in transgenic plants under normal and heat stress conditions. These plants express N-terminal GFP-fused proteins under the control of the 35S promoter. (Upper) Images of true leaves. (Lower) Images of roots. Differential interference contrast (DIC) and GFP fluorescence images as well as merged images are shown. (Scale bars: 20 µm.) (C and D) Validation of interaction between DREB2A and BPM2 by co-IP from transgenic plants either co-overexpressing NSF-BPM2 and GFP-DREB2A (GFP-D2A) in the background of the dreb2a mutant (C) or overexpressing GFP-BPM2 in the WT background (D).
|
Back Print View: 526 |
[ Other News ]___________________________________________________
|