Circadian regulation of plant immunity calcium signalling

为了生存，植物和农作物必须对它们所面临的各种不同的环境刺激做出迅速和适当的反应。关键是区分不同刺激的能力，例如病原体攻击和干旱胁迫。细胞内钙浓度的增加在植物细胞中起到触发作用，激活适当的反应：表达正确的蛋白质来防御特定的胁迫。不同的刺激以不同和独特的特性刺激钙的增加，这种特性被称为“钙信号”，它编码了适当的反应。我们先前已经证明钙调节至少四个不同的转录因子家族(Whalley等人，2011年)，不同的钙信号激活不同的基因集(Whalley和Knight，2013)，我们已经确定了这些钙信号被“解码”的机制(Liu等人，2015；Lenzoni等人，2018)。重要的是，对特定压力的适当反应需要在一天中的不同时间有所不同，以最大限度地保持健康。我们最近发现，对于病原体应激，病原体介导的钙信号的特异性取决于一天中的主观时间，即钙信号，以及随后病原体诱导的基因表达和耐受性，都被生物钟改变。这种由生物钟调节信号通路的形式被称为“门控”，对健康和生存至关重要，但人们对其中涉及的机制或组成部分知之甚少。对这一过程的了解将使育种/工程作物在不断变化的气候中具有更好的适应性。目的：回答以下生物学问题：(I)钙信号是如何受生物钟控制的？这种门控现象涉及哪些时钟成分？(Ii)哪些下游蛋白参与解码这些被昼夜节律时钟修改的新的钙信号？(Iii)哪些转录因子参与识别这些新的钙信号？(Iv)这些新的钙信号被转化为适当的反应的机制是什么？

In order to survive, plants and crops have to respond rapidly, and appropriately, to the multitude of different environmental stimuli they face. Key to this is the ability to discriminate between different stimuli e.g. pathogen attack versus drought stress. An increase in cellular calcium concentration acts as a trigger in plant cells to activate the appropriate response: expressing the correct proteins to defend against a specific stress. Different stimuli provoke calcium increases with different and unique properties, known as "calcium signatures" which encode the appropriate response. We have previously shown that calcium regulates at least four different transcription factor families (Whalley et al., 2011), that different calcium signatures activate different sets of genes (Whalley and Knight, 2013), and we have identified mechanisms by which these calcium signatures are "decoded" (Liu et al., 2015; Lenzoni et al., 2018). Importantly, the appropriate response to a given stress needs to be different at different times of day to maximise fitness. We have most recently found that for pathogen stress the specific nature of pathogen-mediated calcium signature depends on the subjective time-of-day i.e. the calcium signatures, and subsequent pathogen-induced gene expression and tolerance, are modified by the circadian clock. This form of regulation of signalling pathways by circadian clocks is called "gating" and is vital for fitness and survival, yet very little in known about the mechanism or components involved. An understanding of this process would allow the breeding/engineering of crops with improved fitness in a changing climate.Aims:To answer the following biological questions:(i) How are calcium signatures controlled by the circadian clock? What are the clock components involved in this gating phenomenon?(ii) Which downstream proteins are involved in decoding these novel calcium signatures, modified by the circadian clock?(iii) Which transcription factors are involved in recognising these novel calcium signatures?(iv) What is the mechanism by which these novel calcium signatures are converted into the appropriate response?