Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universidad Politécnica de Valencia, 46022 Valencia, Spain.
Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Mol Plant. 2016 Jan 4;9(1):136-147. doi: 10.1016/j.molp.2015.10.003. Epub 2015 Oct 21.
Optimal response to drought is critical for plant survival and will affect biodiversity and crop performance during climate change. Mitotically heritable epigenetic or dynamic chromatin state changes have been implicated in the plant response to the drought stress hormone abscisic acid (ABA). The Arabidopsis SWI/SNF chromatin-remodeling ATPase BRAHMA (BRM) modulates response to ABA by preventing premature activation of stress response pathways during germination. We show that core ABA signaling pathway components physically interact with BRM and post-translationally modify BRM by phosphorylation/dephosphorylation. Genetic evidence suggests that BRM acts downstream of SnRK2.2/2.3 kinases, and biochemical studies identified phosphorylation sites in the C-terminal region of BRM at SnRK2 target sites that are evolutionarily conserved. Finally, the phosphomimetic BRM(S1760D S1762D) mutant displays ABA hypersensitivity. Prior studies showed that BRM resides at target loci in the ABA pathway in the presence and absence of the stimulus, but is only active in the absence of ABA. Our data suggest that SnRK2-dependent phosphorylation of BRM leads to its inhibition, and PP2CA-mediated dephosphorylation of BRM restores the ability of BRM to repress ABA response. These findings point to the presence of a rapid phosphorylation-based switch to control BRM activity; this property could be potentially harnessed to improve drought tolerance in plants.
对干旱的最佳响应对于植物的生存至关重要，并且会在气候变化期间影响生物多样性和作物表现。有丝分裂可遗传的表观遗传或动态染色质状态变化被认为与植物对干旱胁迫激素脱落酸（ABA）的反应有关。拟南芥 SWI/SNF 染色质重塑 ATP 酶 BRM（BRM）通过在萌发期间防止应激反应途径的过早激活来调节对 ABA 的响应。我们表明，核心 ABA 信号通路成分与 BRM 物理相互作用，并通过磷酸化/去磷酸化对 BRM 进行翻译后修饰。遗传证据表明 BRM 作用于 SnRK2.2/2.3 激酶的下游，生化研究在 BRM 的 C 末端区域鉴定到在 SnRK2 靶标位点处的磷酸化位点，这些位点在进化上是保守的。最后，磷酸模拟 BRM（S1760D S1762D）突变体表现出 ABA 超敏性。先前的研究表明，BRM 在存在和不存在刺激的情况下都位于 ABA 途径的靶位，但仅在不存在 ABA 的情况下才具有活性。我们的数据表明，BRM 的 SnRK2 依赖性磷酸化导致其抑制，而 PP2CA 介导的 BRM 去磷酸化恢复了 BRM 抑制 ABA 反应的能力。这些发现表明存在一种基于快速磷酸化的开关来控制 BRM 活性；这种特性可能被潜在地利用来提高植物的耐旱性。
