Constitutive activation of stress-inducible genes in a brassinosteroid-insensitive 1 (bri1) mutant results in higher tolerance to cold
Constitutive activation of stress-inducible genes in a brassinosteroid-insensitive 1 (bri1) mutant results in higher tolerance to cold
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DOI：
10.1111/j.1399-3054.2009.01304.x
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发表时间：
2010-02-01
影响因子：
6.4
通讯作者：
Nam, Kyoung Hee
中科院分区：
文献类型：
--
作者：
Kim, Sun Young;Kim, Beg Hab;Nam, Kyoung Hee
许多植物激素参与协调植物在胁迫下的生长反应。然而，很少有机制研究探讨植物如何维持生长和胁迫反应之间的平衡。类甾醇（BR）是植物特有的甾体激素，在植物的一生中影响植物生长发育的许多方面。在这项研究中，我们确定，BR的外源处理有助于植物克服寒冷条件下，只有当预处理小于1 nM，和油菜素类固醇不敏感1（bri 1）突变，这导致缺陷BR信号和随后的侏儒症，产生增加的耐冷性。相比之下，BRI 1过表达的植物对相同的胁迫比野生型更敏感。我们发现，bri 1突变体和BRI 1过表达的转基因植物含有比野生型更高的CBFs/DREB 1 s的基础表达水平。然而，在野生型、bri 1 -9和BRI 1过表达植物中，代表性的冷胁迫相关基因以相同的模式被调控。为了检查全局基因表达并比较在bri 1 -9和BRI 1-GFP植物中除了CBFs/DREB 1 s之外显示差异表达模式的基因，我们使用cDNA微阵列分析在不存在胁迫的情况下分析差异mRNA表达。内源性表达的两个应力诱导基因以及基因编码的转录因子，驱动应力诱导基因的表达维持在较高的水平比野生型或BRI 1过表达植物中的bri 1 -9。这表明bri 1 -9突变体可以始终对可能在任何时候通过组成性激活防御子集而施加的压力保持警惕。
Many plant hormones are involved in coordinating the growth responses of plants under stress. However, not many mechanistic studies have explored how plants maintain the balance between growth and stress responses. Brassinosteroids (BRs), plant-specific steroid hormones, affect many aspects of plant growth and development over a plant's lifetime. In this study we determined that exogenous treatment of BR helped the plant overcome the cold condition only when pretreated with less than 1 nM, and the brassinosteroid-insensitive 1 (bri1) mutation, which results in defective BR signaling and subsequent dwarfism, generates an increased tolerance to cold. In contrast, BRI1-overexpressing plants were more sensitive to the same stress than wild-type. We found that the bri1 mutant and BRI1-overexpressing transgenic plants contain higher basal level of expression of CBFs/DREB1s than wild-type. However, representative cold stress-related genes were regulated with the same pattern to cold in wild-type, bri1-9 and BRI1 overexpressing plants. To examine the global gene expression and compare the genes that show differential expression pattern in bri1-9 and BRI1-GFP plants other than CBFs/DREB1s, we analyzed differential mRNA expression using the cDNA microarray analysis in the absence of stress. Endogenous expression of both stress-inducible genes as well as genes encoding transcription factors that drive the expression of stress-inducible genes were maintained at higher levels in bri1-9 than either in wild-type or in BRI1 overexpressing plants. This suggests that the bri1-9 mutant could always be alert to stresses that might be exerted at any times by constitutive activation of subsets of defense.