Ryan C A, Pearce G
Institute of Biological Chemistry, Washington State University, Pullman 99164-6340, USA.
Annu Rev Cell Dev Biol. 1998;14:1-17. doi: 10.1146/annurev.cellbio.14.1.1.
Damage to leaves of several plant species by herbivores or by other mechanical wounding induces defense gene activation throughout the plants within hours. An 18-amino acid polypeptide, called systemin, has been isolated from tomato leaves that is a powerful inducer of over 15 defensive genes when supplied to the tomato plants at levels of fmol/plant. Systemin is readily transported from wound sites and is considered to be the primary systemic signal. The polypeptide is processed from a 200-amino acid precursor called prosystemin, analogous to polypeptide hormones in animals. However, the plant prohormone does not possess typical dibasic cleavage sites, nor does it contain a signal sequence or any typical membrane-spanning regions. The signal transduction pathway that mediates systemin signaling involves linolenic acid release from membranes and subsequent conversion to jasmonic acid, a potent activator of defense gene transcription. The pathway exhibits analogies to arachidonic acid/prostaglandin signaling in animals that leads to inflammatory and acute phase responses.
食草动物或其他机械损伤对几种植物叶片造成的损害会在数小时内诱导整株植物的防御基因激活。一种由18个氨基酸组成的多肽，称为系统素，已从番茄叶片中分离出来，当以飞摩尔/株的水平提供给番茄植株时，它是15种以上防御基因的强力诱导剂。系统素很容易从伤口部位运输，被认为是主要的系统性信号。该多肽由一种名为前系统素的200个氨基酸的前体加工而成，类似于动物体内的多肽激素。然而，植物激素原不具有典型的双碱性切割位点，也不包含信号序列或任何典型的跨膜区域。介导系统素信号传导的信号转导途径涉及从膜中释放亚麻酸，随后将其转化为茉莉酸，茉莉酸是防御基因转录的有效激活剂。该途径与动物体内导致炎症和急性期反应的花生四烯酸/前列腺素信号传导类似。
