Rojo E, Titarenko E, León J, Berger S, Vancanneyt G, Sánchez-Serrano J J
Centro Nacional de Biotecnología CSIC, Madrid, Spain.
Plant J. 1998 Jan;13(2):153-65. doi: 10.1046/j.1365-313x.1998.00020.x.
Plants responses to mechanical injury are complex and include the induced expression of defence-related genes. The phytohormone JA has been reported to mediate some of these responses. To elucidate further the signal transduction processes involved, the action of specific agonists and antagonists of known signalling effectors on the response of Arabidopsis thaliana plantlets to JA and wounding was investigated. The identification and characterization of a reversible protein phosphorylation step in a transduction pathway leading to JA-induced gene transcription is reported. This phosphorylation event involved the opposing activities of a staurosporine-sensitive protein kinase, negatively regulating the pathway, and a protein phosphatase, most probably of type 2 A, which activated JA-responsive gene expression. JA activation via this pathway was blocked in the A. thaliana JA-insensitive mutants jin1, jin4 and coi1, and by exogenous application of cycloheximide or auxins. Wound-induced activation of JA-responsive genes was also regulated by this protein phosphorylation step. An alternative wound signalling pathway, independent of JA, was also identified, leading to the transcriptional activation of a different set of genes. This JA-independent pathway was also regulated by a protein phosphorylation switch, in which the protein kinase positively regulated the pathway while the protein phosphatase negatively regulated it. Moreover, a labile protein apparently repressed the expression of these genes. One of the genes analysed, JR3, had a complex pattern of expression, possibly because it was regulated via both of the wound signalling pathways identified. According to the function of an homologous gene, JR3 may be involved in feedback inhibition of the JA response.
植物对机械损伤的反应是复杂的，包括防御相关基因的诱导表达。据报道，植物激素茉莉酸（JA）介导了其中一些反应。为了进一步阐明所涉及的信号转导过程，研究了已知信号效应器的特异性激动剂和拮抗剂对拟南芥幼苗对JA和创伤反应的作用。本文报道了在导致JA诱导基因转录的转导途径中一个可逆蛋白磷酸化步骤的鉴定和特征。该磷酸化事件涉及一种对星形孢菌素敏感的蛋白激酶的相反活性，该激酶对该途径起负调节作用，以及一种蛋白磷酸酶，很可能是2A型，其激活JA反应基因的表达。通过该途径的JA激活在拟南芥JA不敏感突变体jin1、jin4和coi1中以及通过外源施用环己酰亚胺或生长素被阻断。创伤诱导的JA反应基因的激活也受该蛋白磷酸化步骤的调节。还鉴定了一条独立于JA的替代创伤信号通路，导致一组不同基因的转录激活。这条独立于JA的通路也受蛋白磷酸化开关的调节，其中蛋白激酶对该通路起正调节作用，而蛋白磷酸酶对其起负调节作用。此外，一种不稳定蛋白明显抑制这些基因的表达。所分析的基因之一JR3具有复杂的表达模式，可能是因为它是通过所鉴定的两条创伤信号通路进行调节的。根据同源基因的功能，JR3可能参与JA反应的反馈抑制。
