The SWI2/SNF2 Chromatin Remodeling ATPase BRAHMA Represses Abscisic Acid Responses in the Absence of the Stress Stimulus in Arabidopsis
The SWI2/SNF2 Chromatin Remodeling ATPase BRAHMA Represses Abscisic Acid Responses in the Absence of the Stress Stimulus in Arabidopsis
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DOI：
10.1105/tpc.112.105114
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发表时间：
2012-12-01
期刊：
影响因子：
11.6
通讯作者：
Wagner, Doris
中科院分区：
文献类型：
--
作者：
Han, Soon-Ki;Sang, Yi;Wagner, Doris
植物作为固着生物体的生存取决于它们应对环境挑战的能力。这方面的关键是植物激素脱落酸(ABA)。ABA不仅促进种子休眠，而且在遇到水分胁迫的萌发后胚胎中也会触发生长停滞。伴随而来的是更强的脱水耐受性。拟南芥萌发后的ABA反应在很大程度上是由ABA诱导的碱性结构域/亮氨酸拉链转录因子ABA INSENSITIVE5(ABI5)介导的。在这里，我们证明了SWI2/SNF2染色质重塑ATPase Brahma(BRM)功能的丧失导致了萌发后生长停滞期间的ABA超敏反应。在缺乏外源ABA的BRM突变体中，ABI5的表达下调，并在ABA感应下积累到高水平。这种影响可能是直接的；染色质免疫沉淀显示BRM与ABI5基因结合。此外，BRM活性的丧失导致核小体的不稳定，可能抑制ABI5的转录。最后，abi5缺失突变体在萌发后生长停滞时对BRM是上位性的。此外，在没有ABA处理的情况下，BRM突变体典型的营养生长缺陷可以通过降低ABA反应而部分克服，BRM突变体表现出更强的抗旱性。我们建议BRM在平衡增长或压力反应方面发挥作用。
The survival of plants as sessile organisms depends on their ability to cope with environmental challenges. Of key importance in this regard is the phytohormone abscisic acid (ABA). ABA not only promotes seed dormancy but also triggers growth arrest in postgermination embryos that encounter water stress. This is accompanied by increased desiccation tolerance. Postgermination ABA responses in Arabidopsis thaliana are mediated in large part by the ABA-induced basic domain/leucine zipper transcription factor ABA INSENSITIVE5 (ABI5). Here, we show that loss of function of the SWI2/SNF2 chromatin remodeling ATPase BRAHMA (BRM) causes ABA hypersensitivity during postgermination growth arrest. ABI5 expression was derepressed in brm mutants in the absence of exogenous ABA and accumulated to high levels upon ABA sensing. This effect was likely direct; chromatin immunoprecipitation revealed BRM binding to the ABI5 locus. Moreover, loss of BRM activity led to destabilization of a nucleosome likely to repress ABI5 transcription. Finally, the abi5 null mutant was epistatic to BRM in postgermination growth arrest. In addition, vegetative growth defects typical of brm mutants in the absence of ABA treatment could be partially overcome by reduction of ABA responses, and brm mutants displayed increased drought tolerance. We propose a role for BRM in the balance between growth or stress responses.