Sauter Margret
Plant Developmental Biology and Plant Physiology, University of Kiel, Am Botanischen Garten 5, 24118 Kiel, Germany
J Exp Bot. 2015 Aug;66(17):5161-9. doi: 10.1093/jxb/erv071. Epub 2015 Mar 9.
Phytosulfokine (PSK) belongs to the group of plant peptide growth factors. It is a disulfated pentapeptide encoded by precursor genes that are ubiquitously present in higher plants, suggestive of universal functions. Processing of the preproprotein involves sulfonylation by a tyrosylprotein sulfotransferase in the trans-golgi and proteolytic cleavage in the apoplast. The secreted peptide is perceived at the cell surface by a membrane-bound receptor kinase of the leucine-rich repeat family. The PSK receptor PSKR1 from Arabidopsis thaliana is an active kinase and has guanylate cyclase activity resulting in dual-signal outputs. Receptor activity is regulated by calmodulin. While PSK may be an autocrine growth factor, it also acts non-cell autonomously by promoting growth of cells that are receptor-deficient. In planta, PSK has multiple functions. It promotes cell growth, acts in the quiescent centre cells of the root apical meristem, contributes to funicular pollen tube guidance, and differentially alters immune responses depending on the pathogen. It has been suggested that PSK integrates growth and defence signals to balance the competing metabolic costs of these responses. This review summarizes our current understanding of PSK synthesis, signalling, and activity.
植物磺肽素（PSK）属于植物肽生长因子组。它是一种双硫酸化五肽，由高等植物中普遍存在的前体基因编码，这表明其具有普遍功能。前体蛋白的加工过程包括在反式高尔基体中由酪氨酰蛋白磺基转移酶进行磺酰化以及在质外体中进行蛋白水解切割。分泌的肽在细胞表面被富含亮氨酸重复序列家族的膜结合受体激酶识别。来自拟南芥的PSK受体PSKR1是一种活性激酶，具有鸟苷酸环化酶活性，产生双重信号输出。受体活性受钙调蛋白调节。虽然PSK可能是一种自分泌生长因子，但它也通过促进缺乏受体的细胞生长来非细胞自主地发挥作用。在植物中，PSK具有多种功能。它促进细胞生长，在根尖分生组织的静止中心细胞中起作用，有助于珠柄花粉管引导，并根据病原体差异地改变免疫反应。有人提出，PSK整合生长和防御信号以平衡这些反应的竞争性代谢成本。本综述总结了我们目前对PSK合成、信号传导和活性的理解。
