Calcium signatures are decoded by plants to give specific gene responses.
Calcium signatures are decoded by plants to give specific gene responses.
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DOI：
10.1111/nph.12087
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发表时间：
2013-02
期刊：
影响因子：
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通讯作者：
Helen J. Whalley;M. Knight
中科院分区：
文献类型：
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作者：
Helen J. Whalley;M. Knight
钙是一种普遍存在的细胞第二信使，将外界的信息传递给植物细胞。在植物中，许多刺激导致细胞内钙浓度的瞬时升高，这被认为激活了适当的反应（McAinsh & Pittman，2009）。植物能够对任何给定的刺激做出适当的反应，这对生存当然是至关重要的。然而，这导致了一个难题：细胞如何能够区分不同刺激引起的钙升高？一个有吸引力的假设是不同钙升高的特定特征（“钙信号”）可能编码植物中的特定信息（艾伦等人，2001; Love等人，2004; Miwa等人，2006; McAinsh & Pittman，2009; Dodd等人，2010年; Short等人，2012年）。通过将细胞溶质游离钙浓度（[Ca 2 +] c）特征谱与基因表达相关联，研究人员已经假设这种高阶信息编码在响应于例如臭氧而产生的[Ca 2 +] c特征谱中（Short等人，2012）、防御诱导子（Lecourieux et al.，2005）或节点因子（Miwa等人，2006年）。[Ca2+] c信号分布也被假设为编码控制气孔开度的信息（艾伦等人，2001年）。还提出[Ca 2 +] c的昼夜节律和昼夜振荡来指定有关细胞过程计时的信息（Loveet al.，2004年）。我们先前已经证明，在许多情况下，例如氧化应激、寒冷和干旱，钙是刺激感知和基因表达之间的中间体（Knight等人，1996，1997;克莱顿等人，1999; Rentel & Knight，2004;沃利等人，2011年）。由这些不同的应力中的每一个产生的钙信号的具体特征的比较显示它们是实质上不同的（例如相位的数量、幅度和持续时间），与钙信号编码的刺激特异性信息的想法一致。一种更直接的方法来验证钙信号对特定反应的模式，是测试人工施加在植物细胞上的信号的效果。文献报道很少，但在一项研究中，人工施加的[Ca 2 +] c振荡显示能够被保卫细胞解码，需要特定的频率和振幅来介导闭合（艾伦et al.，2001年）。我们希望将联合收割机这种强有力的方法与基因表达的全球测量结合起来，以解决新的钙标记是否可能导致不同的转录组反应这一更广泛的问题。由于钙振荡的频率已显示控制哺乳动物细胞中某些转录因子活化的特异性（Dolmetsch等人，1998），并且细胞内钙的振荡已经在对几种刺激的植物中被证实（坎贝尔等人，1996; Moyen等人，1998;艾伦等人，2001; Miwa等人，2006），我们假设钙振荡的不同特征可能定义植物中不同的转录组学响应。振荡的参数（振幅、频率和脉冲数）可以很容易地定义和比较，这使得这种类型的钙信号非常适合解决钙信号是否可以编码下游基因表达的特异性的问题。
Calcium is a ubiquitous cellular second messenger communicating information about the outside world to plant cells. In plants, many stimuli lead to a transient rise in intracellular calcium concentration, which is thought to activate the appropriate response (McAinsh & Pittman, 2009). It is certainly vital for survival that a plant is able to respond appropriately to any given stimulus. This leads to a conundrum, however: how is the cell able to distinguish between calcium elevations elicited by different stimuli? One attractive hypothesis is that the specific characteristics of different calcium elevations (‘calcium signatures’) might encode specific information in plants (Allen et al., 2001; Love et al., 2004; Miwa et al., 2006; McAinsh & Pittman, 2009; Dodd et al., 2010; Short et al., 2012). By correlating cytosolic free calcium concentration ([Ca2+] c) signature profiles to the expression of genes, researchers have postulated that that such higher-order information is encoded in [Ca2+] c signatures produced in response to, for example, ozone (Short et al., 2012), elicitors of defence (Lecourieux et al., 2005) or nod factors (Miwa et al., 2006).[Ca2+] c signature profiles are also hypothesized to encode information that controls stomatal aperture (Allen et al., 2001). Circadian and diurnal oscillations of [Ca2+] c have also been proposed to specify information on timing of cellular processes (Loveet al., 2004). We have previously demonstrated that calcium is an intermediate between stimulus perception and gene expression in a number of situations, for example oxidative stress, cold and drought (Knight et al., 1996, 1997; Clayton et al., 1999; Rentel & Knight, 2004; Whalley et al., 2011). Comparison of the specific characteristics of the calcium signatures produced by each of these different stresses shows them to be substantially different (eg number of phases, magnitude and duration), consistent with the idea of calcium signature-encoded stimulus-specific information. A moredirectapproachtocorrelatingpatternsofcalciumsignaturesto specific responses is to test the effect of signatures that are artificially imposedonplantcells. Reportsintheliteraturehavebeenfew, butin one study, artificially imposed [Ca2+] c oscillations were shown to be able to be decoded by guard cells, with specific frequencies and amplitudes being required to mediate closure (Allen et al., 2001). We wished to combine this powerful approach of imposing calcium signatures upon plants with global measurement of gene expression to address the broader question of whether novel calcium signatures mightleadtodifferenttranscriptomicresponses. Asthefrequencyof calcium oscillations has been shown to control the specificity of activation of certain transcription factors in mammalian cells (Dolmetsch et al., 1998), and oscillations in intracellular calcium havebeenreportedinresponsetoseveralstimuliinplants (Campbell et al., 1996; Moyen et al., 1998; Allen et al., 2001; Miwa et al., 2006), we hypothesized that different characteristics of calcium oscillations might define different transcriptomic responses in plants. The parameters of oscillations (amplitude, frequency and number of pulses) can be easily defined and compared, making this type of calcium signature ideal for addressing the question of whether calcium signatures can encode specificity to downstream gene expression.