Greasing endocytosis in plants - understanding the role of S-acylation in receptor kinase function and internalisation

受体蛋白是植物在细胞外环境中感知物理信号的主要方式。这包括致病微生物和有益微生物、植物自身细胞壁的状态以及各种植物激素。因此，受体激酶对于控制植物在生长过程中如何平衡资源分配、交易对病原菌的抗性与种子产量或营养生产力是至关重要的。鉴于它们强大的控制和平衡植物对环境反应的能力，它们受到非常严格的监管和控制也就不足为奇了。这一规定的一部分涉及确保在一段时间后从植物表面移除感受到信号的受体激酶，以允许测量和分级的环境监测和竞争感知事件的整合，而不是单一的刺激事件压倒植物。这是通过一种被称为内吞作用的过程实现的，即细胞外缘的蛋白质被内化和破坏。这需要一系列的事件，包括用另一种称为泛素的蛋白质“标记”蛋白质。这标志着标记的蛋白质具有内吞作用。我们最近发现，受体激酶的另一种修饰会影响内吞作用。这种修饰被称为S酰化，涉及一旦受体激酶感受到刺激就向其添加脂肪酸。我们发现，S酰化对于受体的正确作用是必不可少的，也是适当的内吞作用所必需的。S酰化的缺失实际上会通过未知的途径导致更快的内吞作用，从而导致信号强度下降和对刺激的无效反应。在这项工作中，我们想了解为什么失去S-酰化会导致更快的内吞作用，是什么决定了受体S-酰化的发生，以及不能被S-酰化的受体采取的内化途径。这将有助于我们了解受体激酶信号是如何被调控的，从而对外部环境做出适当的反应。受体激酶是植物感知其所处世界的最前线；因此，了解受体激酶的功能对于支持育种和转基因方法以提高病原菌抗性、植物生长和产量或环境或气候挑战(如干旱、洪水、高或低温度或盐度)至关重要。

Receptor kinases are proteins that act as the primary means by which plants perceive physical signals in their extracellular environment. This includes pathogenic and beneficial microbes, the state of the plant's own cell wall and various plant hormones. As a result, receptor kinases are critical to controlling how plants balance resource allocation during growth, trading resistance to pathogens against seed yield or vegetative productivity. Given their powerful ability to control and balance how plants respond to their environment it is no surprise that they are very tightly regulated and controlled. Part of this regulation involves ensuring that receptor kinases that have perceived a signal are removed from the plant surface after a period of time to allow for measured and graded environmental monitoring and integration of competing perception events, rather than a single stimulation event overwhelming the plant. This is achieved through a process known as endocytosis whereby proteins on the outer edge of the cell are internalised and destroyed. This requires a number of events including the "tagging" of the proteins with another protein known as ubiquitin. This marks the tagged protein for endocytosis. We recently discovered that another modification of receptor kinases affects endocytosis. This modification, known as S-acylation, involves adding fatty acids to receptor kinases once they have perceived a stimulus. We found that S-acylation is essential for correct action by a receptor and is necessary for appropriate endocytosis. Loss of S-acylation actually causes more rapid endocytosis through an unknown route and, as a result, leads to poor signal strength and ineffective response to the stimulus. In this work we want to understand why loss of S-acylation causes more rapid endocytosis, what dictates that receptor S-acylation will occur and the route of internalisation taken by receptors that can't be S-acylated. This will help us to understand how receptor kinase signalling is regulated to deliver appropriate responses to the external environment. Receptor kinases are the frontline of how plants perceive their world; understanding how receptor kinases function could therefore be key towards supporting breeding and transgenic approaches to improve pathogen resistance, plant growth and yield or environmental or climate challenge such as drought, flooding, high or low temperature or salinity.